Replacement Dwelling Plans in Bromley

'Replacement dwelling plans' is the everyday name for the set of drawings and supporting documents needed to demolish an existing house and build a new one in its place. It covers two operations that the planning system treats as one project: the demolition of the existing dwelling, and the erection of a new dwelling on the same site. Because the end result is a brand-new home rather than an alteration of the old one, a replacement dwelling is a much bigger undertaking than an extension or a loft conversion, and the plans have to carry a correspondingly heavier burden — they describe a complete new building, from foundations to roof, and they have to prove that its scale is acceptable in planning terms.

In planning language a house is Use Class C3, the dwellinghouse class, and a replacement dwelling keeps the same use — a house replaces a house. What changes is the physical building, and it is the physical change that the plans have to justify. The key questions Bromley will ask are not about use but about size, siting, design, character, neighbour amenity and, on many plots in this borough, the effect on the openness of the Green Belt. The drawings either answer those questions clearly or leave them open, and on a replacement dwelling the size question dominates everything else.

That is what makes replacement dwelling drawings distinctive. Unlike a straightforward new build on an empty plot, a replacement dwelling is measured against something specific: the dwelling it replaces. The plans therefore have to establish, accurately, what the existing house is — its footprint, its volume, its height, its floor areas — because in the Green Belt the new house is compared directly against the 'original' version of that building, and even outside the Green Belt the existing house sets the baseline against which increases in bulk, height and coverage are judged. Good replacement dwelling plans start by drawing the existing house honestly, then design the new one within what the comparison allows.

So when we talk about replacement dwelling plans for a Bromley house we mean a sequenced package: an accurate measured survey of the existing dwelling; existing plans, elevations and sections that record it; volume and footprint calculations that establish the baseline; proposed plans, elevations and sections that show the new home; a site plan and, on rural plots, a landscape and drainage layout; and the planning, design, structural, energy and other supporting information the site needs. The rest of this page explains how each of those is prepared, and why, for this borough and this kind of project.

Before any proposed line is drawn, we settle the single most important fact about your plot: is it in the Metropolitan Green Belt (or on Metropolitan Open Land), or is it ordinary residential land inside the built-up area? This is not a detail — it is the fork in the road that decides how big your new house can be, which policies apply, and how the whole application has to be argued. In Bromley it is a live question on a huge number of plots, because the borough holds the highest proportion of Green Belt of any London borough: in broad terms around half of its land is Metropolitan Green Belt, and a good deal more is Metropolitan Open Land.

If your existing house sits on normal residential land within the built-up area, a replacement dwelling is judged principally on design and impact: whether the new house respects local character and the pattern of development, whether its scale, height and massing sit comfortably with its neighbours, whether it protects neighbouring amenity (light, outlook, privacy), and whether it meets the borough's housing-design and space standards. There is genuine scope here to build a larger, better home than the one you are replacing, provided the design is right. Many of the borough's most successful replacement dwellings are exactly this — a modest post-war house or bungalow on a suburban plot replaced by a well-designed family home.

If your house is in the Green Belt or on Metropolitan Open Land, a completely different and far more restrictive regime applies. National Green Belt policy and Bromley's own Green Belt policies treat most new building in the Green Belt as 'inappropriate development' — harmful by definition and permitted only in very special circumstances — but they make a specific, important exception for the replacement of a building: a replacement dwelling is not inappropriate provided it is in the same use and not 'materially larger' than the one it replaces. That exception is the door through which almost every Green Belt replacement dwelling in Bromley walks, and the whole scheme has to be designed to fit through it.

So the first job of any competent set of replacement dwelling plans in Bromley is to establish the designation of the plot against the adopted policies map, before recommending a strategy and long before drawing a proposed scheme. Get this right and the design brief writes itself — you know your ceiling and you design to it. Get it wrong, or ignore it, and you can spend months designing a house the site will never accept. We check the designation at feasibility, every time, because it is the fact everything else depends on.

A replacement dwelling almost always needs full planning permission, and it is worth being clear why, because people sometimes hope a new house can be built under permitted development. It cannot. Permitted development rights allow certain works to an existing dwellinghouse — extensions, outbuildings, roof alterations within limits — but they do not permit the demolition of a house and the construction of a new one. Building a new dwelling is 'development' in the fullest sense and requires an express grant of planning permission from Bromley. There is no prior-approval shortcut for a knock-down-rebuild of a house, unlike some change-of-use projects.

The application is normally a full planning application (or, where the new house sits within the same residential curtilage and the works are householder in nature, it can sometimes be dealt with as a householder application — but a genuine demolition and rebuild is almost always full). A full application requires a complete set of drawings — existing and proposed plans, elevations and sections, a site plan and location plan — together with the supporting documents the site calls for, and it is assessed against the full development plan: Bromley's Local Plan (adopted 16 January 2019) and the London Plan (2021), read with national policy in the National Planning Policy Framework.

Demolition itself is worth a word. The demolition of a dwellinghouse is generally not something you can simply do; while the demolition of many buildings can be carried out under a 'prior notification' procedure for demolition, the sensible and usual course for a replacement dwelling is to obtain planning permission for the whole scheme — demolition and rebuild together — so that the new house is consented before the old one comes down. Where a building is listed, or in a conservation area, demolition controls are tighter still and separate consents may be required, and Bromley has a great many conservation areas, so this is checked as part of feasibility.

The practical implication is that a replacement dwelling is a full-fat planning project, not a light-touch one, and the plans have to be prepared accordingly. That is not a drawback — it is an opportunity, because a full application is the vehicle through which a genuinely better home is designed and consented. But it means the drawings, the calculations and the supporting case all have to be right, because the council will scrutinise them properly. The rest of this page is about making sure they are.

For a Green Belt or Metropolitan Open Land plot, the whole scheme turns on one phrase from national Green Belt policy: a replacement dwelling is not inappropriate development provided the new building is in the same use and 'not materially larger' than the one it replaces. If the new house passes that test, it is treated as appropriate development and the openness argument is largely won; if it fails, the new house becomes inappropriate development, harmful by definition, and can only be permitted if very special circumstances are demonstrated — a bar that a bigger house almost never clears. So on a Green Belt plot, staying within 'not materially larger' is not a nicety; it is the difference between a scheme that can be approved and one that cannot.

The obvious question is: how much larger is 'materially larger'? The phrase is deliberately not a fixed number in national policy, but Bromley — like most Green Belt authorities — applies a working interpretation, and the borough's position is that an increase of over about 10% would generally be considered material, although this can also depend on design and on how the increase affects openness. That figure is a guideline, not a hard statutory cap, and the real test is the effect on the openness of the Green Belt as a matter of planning judgement — but it is a strong steer, and a replacement that adds only a modest increase in volume, keeps within the existing footprint and height, and reads as no more prominent than the original is on far safer ground than one that adds a big new storey or wing.

Crucially, 'materially larger' is usually assessed by volume, and often also by reference to footprint, height and general bulk — so the plans have to quantify all of them. We prepare volume calculations for the existing (original) house and for the proposed house, set them side by side, and show the percentage change, so that the case officer can see at a glance that the increase is modest and does not harm openness. We also show that the footprint and the height are controlled, that the new house is not spreading across the plot, and that outbuildings and hard surfacing are not quietly adding to the built volume. On a Green Belt replacement, these calculations are as important as the architecture.

It is worth being honest about what this means for ambition. On a Green Belt plot, a replacement dwelling is fundamentally a like-for-like-plus-a-little project, not an opportunity to double the size of the house. The gains come from quality, layout, light and efficiency within a volume very close to the original, not from bulk. A great deal of our value on Green Belt replacements is designing a genuinely better home within that constraint — and telling clients honestly, at the outset, what the constraint is, so that the design brief is realistic from day one rather than a disappointment later.

If the new house is measured against the one it replaces, everything depends on what 'the one it replaces' means — and here there is a trap that catches many owners. In Green Belt policy, the comparison is not against the house as it stands today, complete with every extension it has gained over the years; it is against the 'original' dwelling. Bromley follows the standard national definition of the 'original building': the building as it existed on 1 July 1948 or, if it was built after that date, as it was originally built. Later extensions do not count towards the baseline.

This matters enormously, and it often works against the owner. Suppose you own a modest 1930s house in the Green Belt that has been extended twice since — a rear extension in the 1980s and a side extension in the 2000s. When you come to replace it, the volume you are allowed to build back is measured not against the extended house you actually live in, but against the original, un-extended 1930s house. The extensions you or previous owners added are, in effect, stripped out of the baseline. A replacement that simply matched the current extended footprint could therefore be well over the 'original' size and fail the 'materially larger' test, even though it is no bigger than the house standing today.

The reverse can also be true, and occasionally helps: a house that was built large in the first place, and never extended, has a generous original baseline. And the definition rewards care in the evidence. Establishing what the original dwelling was — its footprint, volume and height as first built or as at 1948 — can require historic maps, old drawings, aerial photographs and rating or valuation records, especially where the house has been much altered. We assemble that evidence as part of feasibility, because the original-dwelling baseline is the number the whole Green Belt case is built on, and an un-evidenced or optimistic baseline is an easy point for the council to knock down.

There is a further point that owners frequently misunderstand: the fact that a house has permitted-development rights to be extended does not mean those extensions count towards the replacement baseline. You cannot 'bank' notional future extensions into the size of a replacement dwelling. The baseline is the original dwelling as defined, full stop. This is exactly the kind of thing we establish clearly and early, because the difference between the extended house and the original house can be the difference between a scheme that works and one that does not.

On a normal residential plot inside Bromley's built-up area — away from the Green Belt and Metropolitan Open Land — a replacement dwelling is a much more open-ended opportunity, and the plans are argued on design and impact rather than on a volume cap. Here there is no 'not materially larger' constraint, and the size of the new house is governed instead by what the plot and the street can comfortably accommodate: the prevailing pattern of development, the scale and rhythm of neighbouring houses, plot coverage and the amount of garden retained, height and massing, and the effect on neighbours' light, outlook and privacy. A well-designed replacement can be substantially larger and better than the house it replaces.

That said, 'no volume cap' does not mean 'anything goes'. Bromley's design policies — principally the general design policy for development and the housing-design policy — expect new homes to respond to local character and context, to be well proportioned, and to sit properly on their plots. The borough is also protective of its suburban character in many areas, and it designates a number of Areas of Special Residential Character where the spacious, verdant, low-density grain of the neighbourhood is specifically protected and where an over-large or over-dominant replacement will be resisted. Chislehurst, parts of Petts Wood, Bickley and other leafy areas contain exactly this kind of designation, so 'ordinary residential' does not always mean 'unconstrained'.

Neighbour amenity is usually the sharpest issue on a built-up-area replacement. Because the new house typically fills more of the plot and rises higher than the modest post-war home it replaces, the plans have to demonstrate that it does not harm the neighbours — no overbearing bulk close to a boundary, no significant new overlooking of neighbouring gardens or windows, no serious loss of daylight or sunlight. We design and draw the scheme to protect amenity from the outset, using set-backs, careful window positioning, and roof forms that keep the massing down, and we show the relationships clearly on the drawings so the case officer can see the impact is acceptable.

Character and density complete the picture. In some parts of the borough the opportunity on a replacement is not just a bigger single house but, on a generous plot, potentially more than one dwelling — subdivision, or a pair of houses in place of one. That is a different project with its own density, amenity and parking tests, but it is worth flagging at feasibility because it can transform the value of a plot. Whether the right answer is one better house or two well-designed ones, the discipline is the same: design to the character and constraints of the specific street, and prove it on the plans.

Bromley's character can be hard to pin down because it is really two places in one borough. It is a substantial, prosperous suburban part of south-east London — Bromley town, Beckenham, Orpington, Chislehurst, Petts Wood, West Wickham, Penge — with the housing stock of a comfortable outer suburb: Edwardian and inter-war family houses, post-war estates, bungalows and 1960s–80s developments, exactly the kind of stock that generates replacement-dwelling projects. And it is, at the same time, the most rural of all the London boroughs, with a deep southern hinterland of farmland, woodland, chalk downland and small historic villages that feels far more like the Kent and Surrey countryside than inner London. Until 1965 it was part of Kent, and much of it still is Kent in all but name.

That rural south is genuinely significant. At Downe, the Grade I listed Down House was the home of Charles Darwin for forty years, from 1842 until his death in 1882; it was here that he developed his theory of evolution by natural selection and wrote On the Origin of Species. The surrounding 'Darwin landscape' of small fields, hedgerows and ancient woodland around Downe, Cudham, Keston and Luxted was proposed as a World Heritage Site and is protected as some of the most valued countryside in the capital. High Elms Country Park nearby runs to around 200 acres and includes a Site of Special Scientific Interest. These are the settings in which the borough's rural replacement dwellings sit, and they are protected accordingly.

The borough's landmarks run from the celebrated to the surprising. Biggin Hill, to the south-east, is famous for its wartime airfield, one of the principal fighter stations defending London during the Battle of Britain, now marked by the Biggin Hill Memorial Museum and ringed by Green Belt. At Chislehurst, the man-made Chislehurst Caves — miles of former chalk and flint mine tunnels — served as a vast air-raid shelter in 1940. To the north, Crystal Palace Park carries the memory of the great glass exhibition hall, moved to the ridge above Penge in 1854 and destroyed by fire in 1936, and its Victorian dinosaur sculptures still stand. Bromley also holds a great many conservation areas, several covering the historic villages and their surroundings.

For a replacement dwelling this context is not decoration — it is constraint and opportunity in equal measure. A replacement in the leafy, spacious streets of Chislehurst or Bickley faces character and Special Residential Character tests; one in the Darwin landscape or the North Downs villages faces the Green Belt 'not materially larger' test and heightened landscape and heritage scrutiny; one on a normal Beckenham or Orpington street faces mainly design and amenity tests with real scope to improve the home. Knowing exactly where your plot sits in Bromley's map — its designation, its character, its history — is the foundation of plans that stand a chance, which is why we always start with the site rather than the scheme.

Replacement dwellings are one of the most common ways the housing stock in a borough like Bromley renews itself. Across the suburban parts of the borough, modest inter-war and post-war houses and bungalows on generous plots are steadily being replaced by larger, better-insulated, better-planned family homes — a pattern driven by the value of the land, the age and inefficiency of the original houses, and families wanting more space without moving away. In the rural south the story is different and slower: replacement dwellings there are tightly controlled by the Green Belt, and the projects that succeed are careful, well-evidenced schemes that respect the 'not materially larger' limit rather than ambitious rebuilds.

That contrast produces a two-tier market that anyone buying a plot for replacement needs to understand. A tired bungalow on a wide plot in Petts Wood or West Wickham is, in planning terms, a genuine opportunity: replace it with a well-designed two-storey house and the site can gain substantial value. A tired bungalow of the same size in the Green Belt near Downe or Cudham is a very different proposition: you can replace it, but only with something not materially larger than the original, so the uplift is far smaller and the case far more delicate. The gap between the two is enormous, and it is decided entirely by the designation of the plot.

Bromley's planning stance reinforces the distinction. The borough has consistently sought to protect its Green Belt and Metropolitan Open Land through the Local Plan, and it is well aware of the pressure that housing demand and the value of rural plots put on that land. Its replacement-dwelling policy is designed precisely to allow the sensible renewal of existing rural homes while preventing the incremental growth in built volume that would erode openness over time — which is why it fixes the baseline at the original dwelling and applies the 'materially larger' test. In the suburbs, meanwhile, the concern is character and amenity, and the design policies and Special Residential Character designations do the work.

For an owner or buyer, the practical lesson is that 'replacement potential' means very different things in different parts of the borough, and the label on the estate agent's particulars is worth little on its own. Potential for what size of house, under which regime, measured against what original baseline, on what plot? The replacement dwellings that go well in Bromley are the ones where those questions were answered honestly, on paper, before anyone committed to a design — and the ones that become expensive disappointments are the ones where the designation and the baseline were assumed. Good plans begin as honest answers to those questions.

The classic Bromley replacement candidate is a small, dated house or bungalow on a plot that is generous relative to the building on it — a single-storey inter-war or post-war bungalow, a compact 1950s–70s house, or a poorly built or badly extended property that is not worth renovating. What these share is a mismatch between the plot and the building: the site could comfortably hold a better, larger home, and the existing house is at or near the end of its useful life. On the drawings, these plots let us show a genuinely improved dwelling that makes proper use of the site — subject, always, to the designation and character constraints.

Bungalows are a particular Bromley story. The borough has a great many of them, especially in areas like Petts Wood, Orpington and West Wickham, and replacing a bungalow with a two-storey house is one of the most common and most valuable replacement projects in the borough. The gain in floor area can be dramatic, but it is also where amenity and character issues bite hardest: a new two-storey house next to remaining bungalows has to be designed with real care so it does not overbear its single-storey neighbours or overlook their gardens. The plans have to show that added height is handled sensitively, which is a design problem we solve at the drawing board.

In the Green Belt and Metropolitan Open Land, the stock that gets replaced is often older rural cottages, small farmhouses, and modest twentieth-century houses on large plots. Here the design challenge is the opposite of the suburbs: not how much bigger to go, but how to build a genuinely better home while staying within a volume very close to the original. The plans have to demonstrate the modest scale of the increase, keep the footprint and height controlled, and show a design that reads as no more prominent in the landscape than the house it replaces — often a more considered, better-proportioned building of similar bulk.

Some houses are better extended or refurbished than replaced, and honest advice about that is part of the service. A structurally sound house with good bones, in a location where replacement offers little size gain, may be better and more cheaply improved than demolished. And some plots simply will not support the ambition the owner has — a Green Belt plot will never yield a house twice the size of the original, whatever the design. We would rather tell you that at feasibility than take a fee to design a scheme that the site cannot accept, and where a plot is marginal we set out honestly what it can and cannot deliver.

Bromley's statutory development plan is the Bromley Local Plan, adopted on 16 January 2019, used alongside the London Plan (2021) to determine applications, and read with national policy in the National Planning Policy Framework. A replacement dwelling is a full planning matter, so unlike a permitted-development change of use it is judged against the full development plan — and knowing which policies apply, and designing the scheme around them, is central to getting a positive decision.

In the Green Belt and on Metropolitan Open Land, the key policies are the borough's Green Belt policies. Policy 49 sets out the borough's overall approach to the Green Belt, protecting and enhancing it so that it continues to fulfil its functions and keeping it permanently open. Policy 50 deals with development in the Green Belt (and Metropolitan Open Land), applying the national tests on inappropriate development and openness. And Policy 51 deals specifically with residential extensions and replacement dwellings in the Green Belt and MOL — the policy that applies the 'not materially larger than the original' test to replacements, controls disproportionate additions, and, notably, provides that proposals to extend a converted or replacement dwelling will not normally be permitted, so that the openness of the countryside is not eroded by successive enlargements.

For every replacement dwelling, in the Green Belt or not, the design and housing policies apply. The general design policy for development expects proposals to respond to local character and context; the housing-design policy addresses the quality of new homes, including the nationally described space standards adopted through the London Plan; and the borough protects its suburban grain through the Areas of Special Residential Character policy, which resists over-large or over-dominant development in designated leafy, low-density neighbourhoods. Where a plot is in or near a conservation area, the conservation-area policies apply, and demolition and design are scrutinised more tightly.

Alongside these sit the practical policies any new home engages: highways, access and parking; trees, landscaping and biodiversity, which matter greatly on rural and leafy plots and now include biodiversity net gain; sustainable drainage and flood risk; residential amenity; and sustainability and energy. A replacement dwelling in Bromley has to answer all of them, and the drawings — site plan, landscape plan, drainage layout, elevations and sections — carry much of that answer. Our job is to design a scheme, and draw it, so that compliance is demonstrated policy by policy, whether the decisive policy is the Green Belt 'materially larger' test or a suburban character and amenity judgement.

A replacement dwelling is a new home, so it has to be a good one — and the plans have to show it meets the standards that apply to new housing. Bromley, like all London boroughs, applies the nationally described space standards, adopted through the London Plan, to new dwellings: minimum gross internal floor areas by number of bedrooms and occupants (for example, a one-bedroom two-person home must be at least 50 square metres, and a one-bedroom one-person home at least 37–39 square metres), minimum bedroom sizes, minimum built-in storage, and minimum floor-to-ceiling heights. The London Plan goes further than the national baseline on ceiling height, expecting at least 2.5 metres over the great majority of the home's floor area rather than the national 2.3-metre minimum.

For most replacement dwellings the space standards are easily met, because the new house is generous by design — but they still shape the plan, and they matter especially where a scheme is tight against the Green Belt volume limit and every square metre has to work. The London Plan also sets out wider design and residential-quality expectations: adequate private outdoor space, dual aspect where possible, good daylight and sunlight to habitable rooms, proper storage, and accessibility, including a proportion of homes designed to be accessible and adaptable (and, on larger schemes, wheelchair-accessible). We design the internal plan to satisfy these from the outset, so the new home is not just larger but genuinely better.

Daylight, outlook and privacy are the design tests that most often decide a suburban replacement. The new house has to enjoy good light and outlook itself, and — just as important — it must not harm the light, outlook or privacy of its neighbours. On a plot where the replacement is taller or closer to a boundary than the house it replaces, this has to be handled with care: window positions that avoid overlooking, roof forms that keep the massing down, and set-backs that protect neighbouring gardens. We design and draw these relationships deliberately, and we show them on the elevations and sections so the case officer can see the impact is acceptable.

Character and appearance run through all of it. Whether the plot is suburban or rural, the new house has to sit well in its context — proportioned properly, using materials that suit the area, with a roofline and massing that respond to the neighbours. In an Area of Special Residential Character or near a conservation area this is a formal policy test; everywhere else it is simply the difference between a design that reads as an improvement and one that jars. Good replacement dwelling plans design the new home to be an asset to its street or its landscape, not an intrusion — and prove it on the drawings.

A replacement dwelling is a complete new building, so unlike an extension or a conversion it needs a full structural design from the ground up — and Crown handles that structure in-house, alongside the architecture, which matters because on a new build the structure and the architecture have to be conceived together. The starting point is the ground. Bromley's geology varies across the borough, from the London Clay of the northern suburbs to the chalk and clay-with-flints of the North Downs in the south, and clay in particular brings shrink-swell behaviour, seasonal movement and the influence of nearby trees — all of which drive the foundation design.

Foundations are the first big decision. Depending on the ground conditions, the presence and proximity of trees (which is a major issue on Bromley's many leafy and rural plots, where mature trees and clay soils together often dictate deeper foundations), and the loads of the new house, the solution may be traditional strip or trench-fill footings, wider or deeper foundations near trees, a reinforced raft, or piles with ground beams on poorer ground. A ground investigation informs the choice, and we design the foundation to suit the actual site rather than assuming — because getting the foundations wrong is both the most expensive mistake on a new build and the hardest to fix later.

Above ground, the superstructure has to be designed as a coherent load path from roof to foundation. Whether the new house is masonry cavity construction, a timber frame, a steel-and-masonry hybrid or something more bespoke, the structural design has to carry vertical loads, resist wind and provide stability, and accommodate the openings, spans and double-height spaces the architecture wants. On a replacement dwelling with generous glazing, open-plan living and perhaps a large opening onto the garden, that often means steel beams and columns integrated carefully into the design, sized and detailed so the architecture is achievable and the building stands up.

Because we design the architecture and the structure together, the openings the design wants are openings the structure supports, the spans are real, and the drawings the builder receives are coordinated rather than contradictory. That coordination is worth a great deal on a new build, where a structural surprise discovered on site — a beam that has nowhere to bear, a foundation that has to go deeper than assumed — costs time and money. We resolve those questions on the drawing board, and carry the structural design from the planning stage through to the detailed construction information the contractor builds from.

A new house is also a complete set of building services — heating, hot water, ventilation, electrics, plumbing and increasingly renewables — and these are designed as part of the whole rather than added on afterwards. On a replacement dwelling the services strategy is bound up with the energy strategy and the structure: where the plant goes, how the ventilation and heating are distributed, where the drainage runs, and how it all coordinates with the structural frame and the architecture. Designing it together avoids the classic new-build problem of services fighting the structure and the architecture on site.

Heating and hot water are the biggest choice, and the direction of travel is decisively away from gas. New homes are moving to low-carbon heating — principally heat pumps — driven by the tightening of the Building Regulations and the forthcoming Future Homes Standard, and a well-designed replacement dwelling is planned around that from the start: space for a heat pump and hot-water cylinder, a heating system (often underfloor at ground level) suited to low-flow-temperature operation, and a fabric-first design that keeps the heat demand low so the system can be modest. Retro-fitting these decisions late is expensive; designing them in is not.

Ventilation is now a serious design item rather than an afterthought, because a modern, airtight new home needs proper, controlled ventilation to stay healthy and free of condensation — typically continuous mechanical extract or, in the most efficient homes, mechanical ventilation with heat recovery (MVHR), which needs ductwork planned into the structure and ceilings from the outset. Electrical design covers not just lighting and power but electric-vehicle charging, provision for solar PV and battery storage, and the smart controls a modern home expects. Water, foul and surface-water drainage complete the picture, and on rural plots may involve private systems.

By designing the architecture, structure and services as one coordinated package, we make sure the new home works as a whole: the plant has somewhere sensible to live, the ducts and pipes have routes that do not clash with beams, the drainage falls where it needs to, and the energy and services strategy is real rather than aspirational. On a replacement dwelling — a one-off, bespoke home — that integration is what separates a comfortable, efficient, well-built house from one that is a running battle of compromises. It is a core part of what we do under one roof.

A replacement dwelling is a brand-new home, and new homes have to meet the energy and carbon requirements of the Building Regulations in full — there is no allowance for it being a 'replacement' of an older, leakier house. That means a SAP energy assessment demonstrating compliance with Part L (conservation of fuel and power), covering the building fabric (insulation and airtightness), the heating and hot-water systems, ventilation and any renewable generation. The design is assessed at the design stage (a design-stage SAP calculation supports the building-regulations submission) and confirmed on completion (an as-built SAP and the Energy Performance Certificate).

The regulatory bar is rising sharply, and any replacement dwelling being designed now should be designed with the next step in mind. The Future Homes Standard is the government's headline change for new homes: it is intended to make new dwellings substantially lower-carbon than under previous standards — in the order of a 75–80% reduction in carbon emissions compared with the 2013 baseline — which in practice means new homes will not use fossil-fuel heating such as gas boilers, will rely on low-carbon heating (principally heat pumps), will have on-site renewable generation (typically solar PV), tighter fabric performance and better airtightness. It is coming into force during the current regulatory cycle, and a home designed today should anticipate it rather than be caught out by it.

The practical implication is a 'fabric first' design: get the insulation, airtightness and glazing right, keep the form efficient, and the heating and renewables can be modest and the running costs low. On a replacement dwelling this is easier than on a retrofit, because you are building new and can design in high performance from the foundations up — thermal-bridge-free detailing, generous insulation, good airtightness, controlled ventilation and a heat pump sized for a low heat demand. Done well, the new home is dramatically more efficient than the house it replaces, which is one of the real, tangible benefits of a replacement over a renovation.

We design the energy strategy alongside the architecture and services from the start, rather than treating SAP as a box-ticking exercise at the end. That means the fabric, the openings, the plant space and the renewables are all planned in, the SAP calculation supports the design rather than forcing late changes, and the finished home genuinely performs. On a bespoke one-off house, designing to comfortably meet — and ideally exceed — the current and imminent standards is both a compliance requirement and a long-term gift to the people who will live there.

A new dwelling needs a properly designed drainage strategy for both foul water (from kitchens and bathrooms) and surface water (rainwater from roofs and hard surfaces), and on a replacement dwelling this has to be designed afresh rather than assumed to be adequate because 'there was a house here before'. Foul drainage usually connects to the public sewer where one is available, but on rural plots in the south of the borough it may rely on a private system — a package treatment plant or, less commonly now, a septic tank — which has its own siting, capacity and regulatory requirements that the drainage layout has to show.

Surface water is where policy has moved most, and it matters on every replacement. The London Plan and Bromley's policies expect sustainable drainage systems (SuDS) that manage rainwater close to where it falls and mimic natural drainage — soakaways, permeable paving, rainwater harvesting, attenuation and green roofs — with the aim of restricting the rate and volume of run-off leaving the site and reducing flood risk downstream. A replacement dwelling is a good opportunity to improve on the original in this respect, and the drainage layout has to demonstrate a genuine SuDS approach rather than simply piping everything to the sewer.

Flood risk has to be checked. While much of Bromley is not at high risk of river flooding, parts of the borough sit near watercourses or in valley bottoms, and surface-water (pluvial) flood risk affects specific areas. Where a plot is in a flood-risk zone or an area of surface-water flood risk, a flood-risk assessment may be required, and the design of the new house — floor levels, resilience, and the SuDS strategy — has to respond. We check the flood-risk position at feasibility so that any constraint is designed for from the start rather than discovered late.

On rural and leafy plots there is a further dimension: the interaction of drainage, trees and ground conditions. Soakaways cannot always be used near buildings or on clay, private treatment systems need suitable ground and setbacks, and drainage runs have to avoid tree roots and root-protection areas. We design the drainage as part of the coordinated package — foul, surface water, SuDS and the site levels together — so the strategy is buildable and compliant, and shown clearly on the drainage layout that accompanies the application.

A replacement dwelling begins with demolition, and while that is often the least glamorous part of the project it carries real legal and practical requirements that the plans and the process have to account for. The sensible course is to secure planning permission for the whole scheme — demolition and the new house together — before anything comes down, so that you are never left with a cleared plot and no consent for what replaces it. Where the existing house is listed or in a conservation area, demolition is far more tightly controlled and may need separate consent, which is one reason the conservation and listing check at feasibility matters so much in Bromley.

Demolition itself has to be carried out safely and lawfully: a demolition notice or prior approval for the method of demolition may be required, asbestos surveys and safe removal are essential in older houses, and the works have to protect neighbouring properties, trees and services. On many Bromley plots there are mature trees protected by Tree Preservation Orders or by conservation-area status, and both the demolition and the new foundations have to be designed to protect them — another reason the arboricultural position is checked early.

The Party Wall etc. Act 1996 is frequently engaged on a replacement dwelling, because although the new house may not share a party wall, the works often involve excavation for new foundations close to neighbouring buildings, or affect a boundary structure. Where excavation within the distances set by the Act takes place near a neighbour's building, or where a boundary wall is affected, notices have to be served and, if the neighbour does not consent, a party wall award agreed through surveyors. This is a separate legal process running alongside planning and building regulations, and it is best anticipated early so it does not delay the build.

The practicalities of a rebuild — site access for demolition and construction plant, protection of the highway and neighbours, temporary works, and the sequencing of demolition and construction — all benefit from being thought through at the design stage rather than left to the contractor to improvise. We design the scheme with buildability in mind and flag the demolition, party wall and tree issues at feasibility, so the project runs smoothly from a standing house to a finished new home.

A replacement dwelling can attract the Community Infrastructure Levy (CIL), a charge on new floorspace used to fund infrastructure, and it is important to understand how it applies because it can be a significant cost — or, handled correctly, a small one. Two CIL charges can apply in Bromley: the borough's own CIL (adopted on 19 April 2021, with a residential rate in the order of £60 per square metre) and the Mayor of London's CIL (the second Mayoral CIL, which for a borough in Bromley's charging band is around £60 per square metre), both charged on net additional internal floorspace.

The word 'net' is the key to CIL on a replacement dwelling. CIL is charged on the net increase in floorspace, so the floorspace of the demolished house is deducted from the floorspace of the new one — you are charged, broadly, only on the additional floor area the new house creates over the old one, provided the existing building has been in lawful use for the required period (generally six of the previous three years, i.e. in continuous lawful use for at least six months in the three years before permission). On a like-for-like replacement in the Green Belt, where the new house is only modestly larger than the original, the net increase — and therefore the CIL — can be small or, in some cases, nil. On a large suburban replacement of a small bungalow, the net increase and the CIL can be substantial.

There is also a self-build exemption from CIL for people building or commissioning their own home to live in, which can remove the CIL liability on a genuine self-build replacement dwelling entirely — but it has strict procedural requirements: the exemption must be claimed and granted before development starts, the correct forms and a commencement notice must be submitted at the right times, and the home must remain the applicant's principal residence for three years. Missing a step can lose the exemption and trigger the full charge plus surcharges, so the CIL process has to be handled carefully and on time.

Beyond CIL, larger schemes can attract planning obligations through a section 106 agreement — though a single replacement dwelling rarely does. What every replacement dwelling now engages is biodiversity net gain, the statutory requirement to deliver a measurable net gain in biodiversity, which affects the landscape and ecology design of the scheme. We flag the CIL position, the self-build exemption where relevant, and the biodiversity requirement at feasibility, and handle the CIL forms and notices at the right points, so there are no expensive surprises after permission is granted.

A replacement dwelling application has to tell the council two clear stories: exactly what is on the site now, and exactly what will replace it — and, in the Green Belt, that the new house is not materially larger than the original. We prepare a full, measured set of drawings and the supporting documents that carry the planning, design and technical arguments, so the application is complete, consistent and straightforward for Bromley to assess and validate first time.

The work follows the recognised RIBA stages. At feasibility (Stage 0–1) we survey the existing house, establish the designation and the original-dwelling baseline, prepare the volume and footprint calculations, and test what the site can support. At concept and developed design (Stages 2–3) we design the new home and prepare the planning drawings: existing plans, elevations and sections that record the house being replaced; proposed plans, elevations and sections showing the new dwelling; a location plan and site plan; and, where the plot needs them, a landscape plan, tree plan and drainage layout. In the Green Belt we make the volume comparison legible on the drawings, so the 'not materially larger' case is easy to read.

Alongside the drawings we prepare the supporting documents the application needs: a planning/design and access statement setting out the design rationale and engaging the relevant policies (in the Green Belt, the replacement-dwelling test under Policies 49–51 and the openness argument; in the suburbs, the character and amenity case); and, depending on the site, arboricultural, ecology and biodiversity-net-gain, drainage/flood-risk, heritage and energy information. Everything is prepared to be internally consistent — the volume calculations match the drawings, the design statement matches the elevations, the drainage matches the site plan.

Once permission is granted we move into technical design and construction information (Stages 4 onwards): the building-regulations package and the detailed construction drawings the builder works from, coordinating the architecture, the full structural design and the building services into one buildable set. Because the same team takes the project from the first measured survey through consent to construction, the drawings your contractor receives are coordinated and complete, and the home that gets built is the home that was designed and consented — not a diluted version compromised by gaps between disciplines.

The process starts with feasibility, and on a replacement dwelling this stage carries more weight than any other. We visit and survey the existing house, check the designation against Bromley's policies map (Green Belt, Metropolitan Open Land, conservation area, Special Residential Character, listing, TPOs), establish the original-dwelling baseline and prepare the volume and footprint calculations, and confirm the strategy and the realistic size of the new home. This is where we give you an honest view of what the site will support, by which route, before you spend money on a full design.

Bromley offers pre-application advice, and on a replacement dwelling it is often worth using — especially in the Green Belt, in a conservation area, in an Area of Special Residential Character, or on any sensitive or borderline scheme. A written steer from the council on the acceptable scale and design reduces the risk of a refusal, flags concerns while the scheme can still be adjusted, and shows the eventual case officer that the proposal has been developed carefully. We advise whether pre-application is worthwhile for your specific plot and prepare it where it adds value.

We then prepare the drawing package and supporting documents and submit them to Bromley through the Planning Portal — as a full planning application (or householder application where appropriate) — and manage the case through validation and determination. The council consults neighbours and statutory consultees, the case officer assesses the scheme against the development plan, and a decision is issued, usually against the standard eight-week target for a householder or minor application (longer for more complex cases). We respond to the case officer's queries, provide additional information, and negotiate amendments where that will secure a positive decision.

Once permission is granted — with conditions, which on a replacement dwelling typically cover materials, landscaping, drainage, trees, biodiversity and sometimes the removal or restriction of future permitted-development rights (particularly in the Green Belt, to protect openness) — we help discharge those conditions and take the scheme forward into the building-regulations and construction drawings. That continuity, from measured survey through consent to construction under one roof, is a real safeguard on a project as significant as replacing a home.

The cost of a Bromley replacement dwelling depends on the plot, the designation and how much of the full service you need — from a straightforward suburban replacement judged mainly on design and amenity, through to a Green Belt scheme requiring careful volume evidence, heritage and landscape input, and a robust openness case. We scope the work to your specific project and give you a clear, fixed fee for our part before any design begins, so you know where you stand, and we set out the design fee separately from the costs that are outside our control.

Separate from our fee, budget for the council's application fee (set nationally and payable to Bromley on submission — the fee for a full application for a new dwelling differs from a householder fee), any pre-application advice fee if you use that service, and the specialist inputs the site needs: a structural engineer's design (which we provide in-house), a SAP energy assessment, a ground investigation, and — depending on the plot — arboricultural, ecology and biodiversity-net-gain, drainage and flood-risk, and heritage assessments. On the build itself, budget for demolition, and remember the CIL position (which, as above, is charged on net new floorspace and may be reduced or removed by the demolition credit or a self-build exemption).

On timescales, feasibility and the measured survey typically take a couple of weeks once we can access the property, the design and planning drawings a few weeks more, pre-application advice (if used) adds further time, and the application itself runs against its determination period — the standard eight-week target for many applications, longer for complex or contested schemes. Green Belt and conservation-area cases, and any that attract objections, can take longer. We give you a realistic programme for your specific scheme at the outset, and manage the application actively to keep it moving.

It is worth remembering where money is actually lost on replacement dwellings: not on careful feasibility and a well-argued application, but on designing to the wrong size (especially against the Green Belt limit), on buying a plot on an optimistic assumption about what it will support, or on a refusal because the volume evidence or the design case was weak. Spending properly on establishing the designation and the baseline, and on getting the design and the drawings right first time, is by far the most cost-effective way to bring a Bromley replacement dwelling to fruition.

Understanding why applications fail is the best way to make sure yours does not, and on replacement dwellings the reasons cluster around a few predictable themes. In the Green Belt, by far the most common reason for refusal is that the new house is materially larger than the original — too much extra volume, a larger footprint, greater height, or a bulkier form — so that it is inappropriate development that harms openness and for which very special circumstances have not been shown. A scheme measured against the current extended house rather than the original, or one that simply overreaches, walks straight into this.

The next most common Green Belt refusal is harm to openness or to the purposes of the Green Belt even where the volume is close to the limit — for example where the new house is more spread out, more prominent in the landscape, or accompanied by extensive new outbuildings, hard surfacing and domestic paraphernalia that collectively erode the open character. Poor design, or a house that fails to respect the rural character of its setting, adds further grounds. This is why the openness case, and the treatment of the curtilage, matters as much as the headline volume figure.

On suburban plots the dominant reasons are different: harm to neighbour amenity (an overbearing or overshadowing house, or one that overlooks neighbours), harm to the character of the area (a house that is too big, too tall or out of keeping with the street, especially in an Area of Special Residential Character or near a conservation area), overdevelopment of the plot (too little garden, too much coverage), and inadequate parking or unsafe access. Failing to meet housing-design and space standards, or losing protected trees, can compound the problem.

Our approach is to anticipate every one of these reasons and answer it in the drawings and documents themselves. We establish the designation and baseline honestly at feasibility, size the scheme to what the site will genuinely support, prepare the volume evidence and the openness or amenity case robustly, and design the new home to respect its context. We are candid with clients when an ambition is unrealistic — a Green Belt plot will not yield a house half as large again as the original, however it is designed — because there is no value in preparing an application designed to fail.

To make the process concrete, consider a common Bromley scenario: a modest 1960s bungalow on a good-sized plot on the rural fringe near Chelsfield, in the Green Belt, that an owner wants to replace with a family house. It is exactly the kind of project the borough sees often, and exactly the kind whose plans have to be threaded carefully through the 'not materially larger' test rather than designed around an ambitious wish list.

At feasibility we survey the bungalow and check the designation. It is in the Green Belt, so Policies 49–51 apply and the new house must not be materially larger than the original. We establish the original-dwelling baseline — here the bungalow as first built in the 1960s, with a small later conservatory stripped out of the baseline because it is not part of the original — and prepare volume and footprint calculations. That fixes the ceiling: the new house has to sit within roughly the original volume, with only a modest increase, and keep its footprint and height controlled. We tell the owner honestly that a two-storey house of double the size is not achievable here, but a well-designed replacement of similar volume, making far better use of the space, is.

The design works within that envelope. Rather than sprawling, the new house uses the roof space and a carefully judged, modest increase in volume to deliver a genuinely better home than the bungalow — more usable rooms, better light, proper insulation and a heat pump — while keeping the footprint close to the original, the ridge height controlled, and the massing no more prominent in the landscape than the bungalow it replaces. The volume comparison is shown clearly on the drawings, side by side, so the case officer can see at a glance that the increase is modest and openness is preserved. The curtilage and hard surfacing are kept restrained so the plot continues to read as part of the countryside.

On the application we prepare existing and proposed plans, elevations and sections, a site plan, the volume and footprint calculations, a design and access statement engaging the Green Belt replacement-dwelling test and the openness argument, and the arboricultural, drainage, biodiversity and energy information the plot needs. Submitted through the Planning Portal and managed through Bromley's determination, a scheme like this goes in as a genuine, well-evidenced replacement the council can approve — not an over-large rebuild hoping to slip through. Once permission is granted, the same coordinated team engineers and details the new home through to construction, so the house that gets built is the house that was designed and consented.

Getting consent is not the end of the story, particularly in the Green Belt, and it pays to understand what the permission does and does not allow afterwards. Replacement dwellings in the Green Belt are frequently granted with conditions that remove or restrict the usual householder permitted-development rights — the rights that ordinarily let a homeowner extend, add outbuildings, or put up hard surfacing without a fresh application. The council imposes these conditions precisely to protect openness, so that the modest volume it has just permitted is not incrementally enlarged later by extensions and outbuildings that would each erode the countryside a little more.

This links directly to Bromley's replacement-dwelling policy, which provides that proposals to extend a converted or replacement dwelling will not normally be permitted. The logic is straightforward: the whole basis on which a Green Belt replacement is allowed is that it is not materially larger than the original, so allowing it to be extended afterwards would undo the very control that made it acceptable. In practice this means that, once a Green Belt replacement is built, the owner should expect little or no scope to extend it further — a point worth understanding before the design is finalised, so that the new house is planned to be the finished article rather than a first phase.

The practical consequence is that the design brief for a Green Belt replacement should assume the house is complete on completion. If a family needs more space, that space has to be designed in from the start, within the permitted volume, rather than left for a future extension that will not be allowed. This is one more reason the feasibility and the design matter so much: the volume you are permitted is, realistically, the volume you keep, so it has to be used to its very best effect in the original design.

On suburban plots the position is more relaxed — a replacement dwelling generally retains normal permitted-development rights unless a specific condition removes them — but even there, over-development of the plot can be resisted and future extensions judged on their own merits. We advise on the conditions likely to attach to your specific scheme, and design the new home so that it is the home you actually want, complete, rather than one that depends on future works that may never be permitted.

A great deal of the risk in a replacement dwelling is decided before you own the property, at the point of purchase — and in Bromley, where the designation of the plot makes the difference between a straightforward, valuable suburban replacement and a tightly capped Green Belt one, due diligence before you buy is the most valuable money you can spend. A house marketed as having 'huge potential' or 'scope to extend or replace' may in fact be in the Green Belt, where the replacement can be barely larger than the original, so the potential is a fraction of what a buyer assumes.

The questions to answer before committing are the same ones that decide the application. Is the plot in the Green Belt or on Metropolitan Open Land, or is it ordinary residential land? If it is in the Green Belt, what is the original-dwelling baseline, and how big a house does the 'not materially larger' test actually allow? Is the plot in a conservation area or an Area of Special Residential Character, which will constrain design and scale? Are there protected trees, or clay and mature trees that will drive deep, expensive foundations? Is the existing house listed, which changes demolition entirely? What is the flood-risk and drainage position? Each of these can turn a promising purchase into a very different, or much smaller, opportunity.

We are frequently asked to assess a property before purchase, and it is work we are glad to do, because it protects buyers from expensive mistakes. A short, honest feasibility assessment before you exchange can confirm the designation, establish the likely baseline and the realistic size of a replacement, flag the trees, drainage and heritage issues, and give you a clear-eyed view of what the plot will support. That is far cheaper than buying on an assumption and discovering afterwards that the Green Belt caps the replacement at a size you did not expect.

For self-builders and investors alike, the discipline is the same: never rely on a selling agent's optimism, and never assume that a big plot means a big replacement house. In this borough the answer lies in the designation, the original-dwelling baseline and the site constraints — and all of them can be checked before you commit. Getting that assessment done up front, expressed as a short feasibility view, turns a risky purchase into an informed decision and sets the whole project up to succeed.

Crown Architecture designs, engineers and details replacement dwellings across Bromley and the surrounding Kent and Surrey area, and we do it as a single coordinated service: the planning and designation strategy, the architectural design, the full structural engineering and the building services under one roof. On a replacement dwelling — a complete new home — that integration is not a nicety. The structure and the architecture have to be conceived together, the energy and services strategy has to be designed in from the start, and the whole package has to be coordinated so the house that gets built is the house that was designed. Splitting these disciplines up is how new builds go over budget and lose quality.

We know the Bromley context: a borough that is roughly half Green Belt and Metropolitan Open Land, rich in conservation areas and Areas of Special Residential Character, where the designation of the plot decides the size of the house, where the 'not materially larger' test and the original-dwelling baseline decide real applications, and where clay soils and mature trees shape the foundations. We use that knowledge to give you honest advice at feasibility — including telling you plainly what the site will and will not support — and to design and draw applications, whether a generous suburban replacement or a carefully judged Green Belt one, that are designed to pass.

Just as importantly, we are straightforward to work with. We establish the designation and the baseline early and honestly; we quote a clear fixed fee; and we prepare a coordinated, self-consistent package — drawings, volume evidence, design statement and technical information that all line up — that a case officer can approve without having to fill in the gaps. Then, once permission is granted, the same team engineers and details the new home through to the construction drawings your builder needs, keeping the design intent intact from the first sketch to the finished house.

We also stay with the project after the drawings are done. We manage the application through Bromley's validation and determination, respond to the case officer, negotiate amendments where that will secure a positive decision, help discharge conditions, and carry the scheme into building regulations and construction. The aim is a single, accountable point of contact from the first measured survey to a finished, better home on your plot — and the confidence that comes from having architecture, structure and services designed together by one practice. If you are considering replacing a house in Bromley, we would be glad to give you a free, honest assessment of what your plot will support.