Knock Down and Rebuild in Bexley

In everyday language, a knock-down-and-rebuild is exactly what it sounds like: you demolish the house that is there and build a new one in its place. In planning terms this is called a 'replacement dwelling', and the phrase matters because it captures the two things the council is really deciding on — the loss of the existing building through demolition, and the creation of a new dwelling to replace it. Both sit within Use Class C3, the dwellinghouse class, but the important point is that you are not changing a use or adapting a building. You are removing one home and constructing another.

That distinction shapes everything that follows. Because you are proposing a genuinely new building, the design of the replacement dwelling is assessed on its own merits, from a blank sheet, against Bexley's Local Plan. There is no starting assumption that 'it was a house before, so a house is fine' — the council looks at whether the specific new home you propose is acceptable in its size, height, footprint, siting, appearance, relationship to neighbours and impact on the character of the street. A replacement dwelling can be refused even though the plot has always had a house on it, if the new house is the wrong size, in the wrong place, or out of keeping with its surroundings.

It is also worth being clear about what a replacement dwelling is not. It is not an extension, however large — an extension keeps and adapts the existing house, whereas a rebuild removes it. It is not a conversion, which changes a building's use while keeping the fabric. And it is not, in the normal course of things, permitted development: while there are narrow permitted development routes to demolish certain buildings and, separately, to build new homes in very specific circumstances, a standard knock-down-and-rebuild of a family house is a full planning application for a new dwelling. Anyone who has heard that 'you can rebuild what was there without permission' should set that idea aside — the rebuilt house has to earn its own consent.

Finally, a knock-down-and-rebuild is a project with two halves that have to be handled together: the demolition of the old house and the construction of the new one. Each has its own controls — demolition has its own notification and safety requirements and its own party-wall implications for neighbours, while the new dwelling needs full planning permission and a complete set of Building Regulations. A well-run rebuild treats these as one continuous project, designed and sequenced together, rather than as two disconnected exercises, so there are no gaps between tearing down and building up.

For a knock-down-and-rebuild in Bexley, the answer is almost always yes — the replacement dwelling needs full planning permission. Building a new house is not something you can do under the permitted development rights that let existing homeowners add extensions or convert lofts, because those rights apply to alterations of an existing dwelling, not to the creation of a new one. When you demolish the existing house and build another, you are proposing a new dwelling, and a new dwelling is a full planning matter.

This surprises some people, because there are permitted development rights connected with both demolition and new homes — but neither delivers a normal rebuild without permission. There is a permitted development right that allows the demolition of certain buildings subject to a 'prior approval' process for the method and timing of demolition, but that controls how you demolish, not whether you can build a replacement, and it does not grant you a new house. Separately, recent permitted development rights allow, in narrow circumstances, the construction of new homes — for example additional storeys on existing blocks, or the replacement of certain vacant commercial and light-industrial buildings with homes — but these are tightly drawn and do not cover the everyday case of flattening a suburban house and rebuilding it. For the great majority of Bexley rebuilds, the route is a full planning application for the replacement dwelling.

The practical consequence is that you should never start demolition on the assumption that the rebuild is 'permitted'. Doing so risks a situation where the old house is gone but the new one has no consent, which is the worst of all positions — an empty plot, no home, and a design that then has to satisfy the council from a position of weakness. The correct order is always to secure planning permission for the replacement dwelling first, deal with the demolition controls and party-wall obligations, and then demolish and build. That sequence protects your investment and keeps the whole project on solid legal ground.

There is one important nuance for demolition itself. Even where you have planning permission for the new house, the demolition of the old one usually requires a separate 'prior notification' to the council under the demolition permitted development right, giving details of the demolition method and any site restoration, and the council has a short period to decide whether it needs to approve those details. In conservation areas, demolition is controlled more tightly still. We handle the demolition notification and the planning application as parts of one coordinated process, so nothing falls through the gap between the two.

The first honest question on any rebuild is whether it is actually the right project. For many Bexley houses, extending and refurbishing is the better answer: it is usually cheaper, it keeps you within permitted development for parts of the work, it avoids CIL on much of the floorspace, and it can deliver an excellent home. A rebuild only makes sense when the existing house is genuinely holding you back — and part of our job at feasibility is to tell you which camp your project is really in, rather than assuming the most expensive option.

A rebuild tends to win where the existing building is small, poorly built or structurally compromised, so that money spent adapting it is money spent shoring up something you will never be fully happy with. It wins where the layout is fundamentally wrong and cannot be fixed by extension — where the only way to get the home you want is to start with a clean footprint. It wins where the fabric is so poor that reaching modern energy performance is impractical, and where a new, highly insulated dwelling built to current standards will be far cheaper to run and more comfortable. And it can win on plots where a well-designed new house simply makes far better use of the land than the tired original ever did.

Extending tends to win where the existing house is sound and characterful, where the changes you want are additive rather than transformative, where retaining the building avoids CIL and keeps some permitted development rights in play, and where the plot or the policy context would not support a materially bigger or different replacement. In a conservation area or on a locally listed building, keeping and extending the existing fabric may also be strongly preferred on heritage grounds. The right answer is specific to the house, the plot and the outcome you want.

We model both paths at feasibility for anyone weighing a rebuild against a major extension: what each would deliver, roughly what each would cost, how each is treated for planning and CIL, and which gives you the home and the value you are after. That comparison, done properly before any commitment, is one of the most useful things an architect-and-engineer practice can give you — because the biggest mistakes in this area are made not on site but in choosing the wrong project in the first place.

A Bexley knock-down-and-rebuild is decided against the borough's development plan, and knowing which policies apply lets us design the new home to satisfy them rather than hoping to by accident. Bexley adopted its current Local Plan on 26 April 2023. It runs to 2038 and replaced the earlier Bexley Core Strategy and the remaining saved policies of the old Unitary Development Plan, so it is the up-to-date framework against which your replacement dwelling will be judged, alongside the London Plan and national policy.

Several Local Plan policies are directly relevant to a rebuild. Policy DP1 (providing a supply of housing) supports the effective and efficient use of land for housing and expects new homes to comply with, and where possible exceed, the relevant minimum space standards. Policy DP2 (residential development on backland and infill sites) governs new dwellings on backland and infill plots — relevant if your rebuild increases the number of homes or sits on a subdivided or backland site. Policy DP11 (achieving high-quality design) requires development to contribute positively to the street scene through its massing, layout and detailing and to respond to local character. Policy DP12 (tall buildings and building heights) sets the council's approach to height, expecting new development to respond positively to its local context — important because a common rebuild question is whether the new house can be taller than the old one.

For a straightforward one-for-one rebuild of a single house, the central tests are design and character (DP11), scale and height in context (DP12), residential quality and space standards (DP1 and the London Plan), and the impact on neighbours' amenity. The council will look closely at whether the replacement dwelling sits comfortably in its street — its footprint, height, roof form, materials and relationship to the building line and to adjoining houses — and whether it protects the daylight, sunlight, privacy and outlook of neighbours. A rebuild that respects the rhythm and character of its street and treats its neighbours fairly is working with the grain of these policies; one that is simply the biggest box the plot can hold is working against them.

The Local Plan is supported by the council's Design Guide Supplementary Planning Document, whose first part (Design Principles) was adopted in January 2025 and whose later parts, including small-sites guidance, followed in 2026, replacing the older Design and Development Control Guidelines and related documents. This guidance expands on the Local Plan's design themes — local character, townscape, materials and details, spatial quality — and sets out in more detail how the council expects new homes to be designed in the Bexley context. Our job is to design the replacement dwelling, and write the supporting statements, to answer these documents policy by policy, so the case officer can recommend approval without having to fill gaps.

The single biggest planning judgement on most Bexley rebuilds is whether the new house is the right size and shape for its plot and its street. Unlike the loss-of-facility test that dominates pub conversions, a replacement dwelling usually turns on design: does the new home respect the established character, building line, height, spacing and roof form of its surroundings, or does it dominate them? Bexley is a borough of distinct residential characters — inter-war and post-war suburban estates, older village cores, riverside areas and pockets of larger detached houses — and what is appropriate in one is not appropriate in another.

The council will look at the footprint of the new house relative to the plot and to neighbouring houses; its height and the number of storeys, including any accommodation in the roof; the roof form and pitch and how they sit against adjoining roofs; the position of the house on the plot, including its distance from boundaries and its relationship to the established building line; the width of gaps to neighbours, which give suburban streets their sense of openness; and the materials and detailing. A rebuild that keeps to the pattern of its street — similar height and building line, comparable gaps to neighbours, a roof and materials that sit well against its neighbours — is far more likely to gain consent than one that pushes forward of the building line, towers over its neighbours, or fills the plot to its edges.

A frequent aspiration is to build bigger than the house that is being removed — a larger footprint, an extra storey, rooms in the roof, a deeper plan. This is often achievable, but it is not automatic. The increase has to be justified in design terms: it has to sit comfortably in the street, not harm neighbours' daylight, sunlight, privacy or outlook, and not over-develop the plot. The old house's size is a reference point, but the real test is whether the new house is acceptable in its context, not simply whether it is bigger or smaller than what was there. We design to find the largest, best home the plot and the policies will genuinely support — which is usually more than a nervous approach would attempt and less than an over-ambitious one.

Overlooking, overshadowing and loss of privacy are where many rebuilds run into neighbour objections and, sometimes, refusal. A taller or deeper new house, or one with windows in new positions, can affect the amenity of adjoining properties in ways the old house did not. We design the new dwelling with these relationships in mind from the start — setting heights, roof forms, window positions and separation distances so that the new home is a good neighbour — and we show that clearly on the drawings, because a scheme that visibly respects its neighbours is a scheme a case officer can defend.

A significant part of the London Borough of Bexley lies within the Metropolitan Green Belt, particularly in the south and east of the borough around the fringes towards the Kent countryside. If the house you want to knock down and rebuild sits in the Green Belt, the rules are considerably stricter, and it is essential to establish the Green Belt position at the very start, because it changes what kind of replacement is acceptable.

National Green Belt policy treats most new building as inappropriate development, harmful by definition and permitted only in limited exceptions. One of those exceptions is the replacement of an existing dwelling — but the replacement is only acceptable where it is in the same use and not materially larger than the building it replaces. The whole thrust of Green Belt policy is to preserve openness, so a Green Belt rebuild is judged above all on whether the new house would be materially larger, or would spread further across the site, than the one it replaces. A like-for-like replacement of similar size and footprint has a route; a substantially bigger house does not.

Bexley's approach reflects this. The council will consider a replacement of an existing lawful dwelling in the Green Belt on its merits, but it resists proposals that increase the number of dwelling units, that materially increase the size or living accommodation, or that harm the openness and character of the Green Belt. A rebuild that swaps a modest house for a much larger one, or that adds units, will struggle unless very special circumstances can be shown — a high bar that is rarely met. The council may also impose conditions removing future permitted development rights on a Green Belt replacement, precisely to stop the new house being extended later in ways that would erode openness.

None of this makes a Green Belt rebuild impossible — a well-judged, similarly sized replacement of a genuinely existing dwelling can be entirely achievable — but it makes the size, siting and openness of the new house the decisive issues, and it makes early, honest advice essential. We check the Green Belt designation, establish the size and lawful status of the existing dwelling, and design a replacement that stays within what Green Belt policy allows, supporting it with the evidence the council needs. Where an aspiration for a much larger house is simply incompatible with the Green Belt, we tell you at feasibility rather than after an expensive refusal.

Some knock-down-and-rebuild projects are not one-for-one. A generous plot may tempt an owner or developer to demolish one house and build two, or to rebuild the main house and carve a new plot out of the garden, or to build a new dwelling on backland behind existing houses. These schemes are still rebuilds in part, but they engage Bexley's policies on backland and garden-land development, and those bring extra scrutiny.

Policy DP2 (residential development on backland and infill sites) is the key policy here. It supports appropriately located new homes on small sites where access, amenity and landscaping are satisfactorily addressed — but it is alert to the problems that garden and backland development can cause: cramped layouts, awkward or unsafe access, loss of the spacious, green character that defines much of suburban Bexley, harm to neighbours through overlooking and noise from new access, and the 'garden-grabbing' concern that gardens are a resource in their own right. A scheme that adds dwellings on garden or backland has to show it does not harm the character of the area or the amenity of neighbours and that it can be accessed and serviced properly.

The distinction between a straightforward replacement and an intensification matters for the whole application. A one-for-one rebuild is judged mainly on the design of the new house; a rebuild that increases the number of homes, or that relies on subdividing a plot, is judged additionally on density, access, the character of the wider area and the cumulative effect of that kind of development in the neighbourhood. It is entirely possible to over-reach here — to propose more units than the plot can carry to a good standard — and over-development is a common reason such schemes are refused.

We assess honestly, at feasibility, whether a plot can support more than a one-for-one replacement, and if so how many homes it can carry to Bexley's standards without harming character, amenity or access. Where the plot genuinely supports additional homes, we design a layout that answers Policy DP2 head-on; where it does not, we say so, because there is no value in a scheme that crams in units at the cost of the very qualities the council is trying to protect.

Bexley sits on the south-eastern edge of Greater London, straddling the boundary between the metropolis and the Kent countryside, with the River Thames along its northern edge and the chalk of the North Downs rising to the south. The modern London Borough of Bexley was formed in 1965 from a group of older towns and parishes — Bexley and Old Bexley, Bexleyheath, Sidcup, Erith, Crayford, Welling and Belvedere among them — each with its own history, high street and distinct residential character. That patchwork of characters is why replacement dwellings here have to be judged place by place: the right new house for a 1930s Sidcup avenue is not the right house for an Erith riverside street or an Old Bexley village lane.

The borough's housing stock is, above all, suburban. Much of Bexley was built out in the great inter-war expansion of the 1920s and 1930s, when the railways and the arterial roads opened the area up and estate after estate of semi-detached and detached houses went up on former farmland — the archetypal metroland suburb. Post-war building added more, including estates rebuilt after wartime damage in the north of the borough. It is this stock — modest, sometimes poorly built, on generous plots, with dated layouts and weak energy performance — that generates so many of the borough's knock-down-and-rebuild projects, because the plots are good and the original houses have often reached the end of their useful lives.

Bexley has a surprisingly rich heritage for somewhere so associated with twentieth-century suburbia. Hall Place, near Bexley village, is a striking country house begun around 1537, its chequered flint-and-stone frontage and formal gardens a survival from the Tudor age. Danson House, in Danson Park, is a Palladian villa built in 1765 by the architect Sir Robert Taylor for a wealthy City merchant, with grounds laid out in the manner of 'Capability' Brown. In Bexleyheath stands the Red House, the home William Morris built and furnished in 1860 — a founding building of the Arts and Crafts movement, now in the care of the National Trust. The north of the borough tells an industrial story: Erith grew from a riverside resort into a busy Thames-side port, and at Crossness, Joseph Bazalgette's great sewage pumping station of 1865 stands as one of the finest monuments of Victorian engineering.

For a rebuild, this context is planning-relevant, not just colour. Bexley has numerous conservation areas — among them Old Bexley, Lesney Park Road in Erith, Iron Mill Lane and Star Hill in Crayford, and Longlands Road and The Oval in Sidcup — and many listed and locally listed buildings. Demolition and rebuild in or near these areas faces additional heritage controls: in a conservation area, the demolition of a building that contributes to the area's character is tightly controlled, and the design of the replacement is held to a higher standard. Parts of the north also lie near the Thames and its tributaries, where flood risk affects design. Knowing exactly where your plot sits in Bexley's map, its character areas and its constraints is the starting point for a credible rebuild.

The knock-down-and-rebuild market in Bexley is, in large part, a product of the borough's own history. The vast inter-war and post-war housebuilding that created suburban Bexley produced tens of thousands of modest semi-detached and detached houses on generous plots. Ninety or a hundred years on, many of those houses have reached a stage where their fabric, layout and energy performance are hard to reconcile with modern expectations — while the plots they sit on remain highly desirable. That gap between a tired house and a good plot is exactly what drives rebuilds.

For decades the default response to an outdated Bexley house was to extend it — a rear extension, a loft conversion, a side return — and for many houses that remains the sensible path. But as construction standards, energy expectations and buyers' aspirations have risen, more owners and developers have concluded that a comprehensive new dwelling delivers a better home and better value than repeatedly patching an old one. Rising land values relative to the value of the ageing houses reinforce this: on a good plot, a well-designed new house can be worth substantially more than the original, which makes the economics of a rebuild stack up in a way they did not a generation ago.

At the same time, the policy framework around rebuilds has become more sophisticated. The 2015 nationally described space standard and the London Plan's design and space policies set clear expectations for the quality of new homes; the 2021 uplift to the Building Regulations and the coming Future Homes Standard have transformed the energy and carbon requirements for new dwellings; and the introduction of the Community Infrastructure Levy in Bexley means that net additional floorspace now carries a charge. A rebuild today is a more regulated, higher-specification exercise than it once was — which is precisely why designing it as a coordinated whole, from planning through structure and services to energy and CIL, matters so much.

The result is a considered market. Genuinely tired houses on good plots are being replaced with high-quality new homes, often transforming both the individual property and, done well, the street. Bexley's task is to make sure those replacements respect the character that makes its suburbs attractive, protect neighbours, and meet the standards a new home is held to — and the rebuilds that proceed smoothly are the ones that meet the council on that ground rather than treating a new house as a licence to build the biggest possible box.

A knock-down-and-rebuild is a rare opportunity: a genuinely blank sheet on which to design a home exactly around how you want to live. But that freedom comes with the standards every new dwelling must meet, and designing to them from the first sketch is what separates a smooth application from a frustrating one. The key residential benchmarks are the nationally described space standard and the London Plan's housing design policies, both of which Bexley applies to new homes through its Local Plan.

The nationally described space standard, introduced on 27 March 2015, sets minimum gross internal floor areas for new homes by the number of bedrooms and occupants — for example, around 37 to 39 square metres for a one-bedroom, one-person home, 50 square metres for a one-bedroom, two-person home, and around 70 square metres for a two-bedroom, three-person home over two storeys, with larger minimums for family houses. It also sets minimum bedroom sizes — a single bedroom of at least 7.5 square metres and at least 2.15 metres wide, a double of at least 11.5 square metres — and minimum built-in storage and floor-to-ceiling heights. For a rebuild these are floors, not targets: a well-designed new family house will usually exceed them comfortably, but every room and the dwelling as a whole must at least meet them.

Beyond raw floor area, a good rebuild is designed for light, outlook, flexibility and comfort. That means orientating living spaces to the sun where the plot allows, giving every habitable room proper daylight and outlook, planning circulation efficiently so space is not wasted, providing generous storage, and thinking about how the house will work over time — for a growing family, for working from home, for later life. It also means designing genuine private amenity space — a garden or terrace of a usable size and shape — which Bexley, as a relatively green outer-London borough, takes seriously, along with practical provision for parking, cycle storage, and refuse and recycling.

The design also has to reconcile your ambitions with the external constraints discussed earlier — the character of the street, the height and building line, the relationship to neighbours. The best rebuilds achieve both at once: a home that is exactly right on the inside and a good neighbour and townscape citizen on the outside. We design from both directions simultaneously, testing internal layouts against the space standard and external form against the street and the neighbours, so the home you fall in love with on paper is also the home the council can approve.

A knock-down-and-rebuild is a complete new structure, and that is where an architect-and-engineer practice earns its keep. Unlike an extension, which ties into an existing building, a rebuild has to be engineered in its entirety — foundations, superstructure, floors, roof and every connection — and the structural design has to be developed alongside the architecture, not bolted on afterwards. Crown handles the structure and the architecture together, so the home you get consent for is one that has been engineered to be built.

It starts underground. The foundations of a new dwelling depend on the ground conditions and on what the site has been through, and both need investigating rather than assuming. Bexley's geology varies across the borough — alluvium and made ground near the Thames in the north, London Clay and chalk further south — and clay soils in particular bring shrinkage and heave risks, especially where trees are near, that drive foundation design. The demolition of the old house, and any old foundations, cellars, drains or made ground it leaves behind, also affects what the new foundations have to deal with. A site investigation and, where needed, a soil report inform whether trench-fill, deeper strip, pile or raft foundations are appropriate, and how they must be detailed near trees, boundaries and drains.

Above ground, the superstructure has to be designed as a coherent load path from roof to foundations. A modern rebuild might be masonry cavity-wall construction, a timber or steel frame, or a hybrid; whatever the choice, the walls, floors and roof have to carry their loads safely, resist wind, and accommodate the openings, spans and cantilevers that contemporary designs love — large glazed openings, open-plan spaces, first-floor overhangs, and roof forms that create rooms in the roof. Each of these has a structural consequence: big openings need beams and proper support; open-plan layouts need the loads above carried across the space; rooms in the roof need the roof structure designed to be habitable. We size and detail all of this with calculations, so the striking spaces on the architectural drawings are genuinely deliverable.

Because we design the structure and the architecture as one, the planning drawings you submit are already structurally coherent — the beams, foundations and load paths are understood, not discovered later. That avoids the classic rebuild problem, where a beautiful planning design turns out to need clumsy structure to stand up, forcing awkward compromises on site. It also means that when the scheme moves to Building Regulations and construction, the structural package flows straight out of the design rather than being reverse-engineered into it — which is faster, cheaper, and far less prone to costly surprises.

A new dwelling is not just a structure and a set of rooms; it is a set of systems — heating, hot water, ventilation, electrics, water, drainage and increasingly on-site generation — that have to be designed as an integrated whole. On a rebuild you are specifying all of these from scratch, which is both a freedom and a responsibility: you can build in the comfort, efficiency and future-proofing that an old house could never offer, but only if the services are designed alongside the architecture and structure rather than squeezed in afterwards.

Heating and hot water are the centrepiece, and the direction of travel is decisively low-carbon. New homes are moving away from gas boilers towards heat pumps — air-source or, on suitable plots, ground-source — which changes the design: heat pumps work best with well-insulated fabric and lower-temperature emitters such as underfloor heating or larger radiators, and they need space for the unit and, in some cases, a hot-water cylinder. Designing the fabric, the emitters and the plant together is what makes a heat-pump home comfortable and efficient. Ventilation matters just as much: a well-sealed modern home needs a proper ventilation strategy — often mechanical ventilation with heat recovery (MVHR) — to keep the air fresh and healthy without throwing away heat.

Then there are the everyday systems that a whole new house needs designed and coordinated: the electrical layout and consumer unit, sized for modern loads including electric heating and vehicle charging; the incoming water supply and internal plumbing; the foul and surface-water drainage; data and networking; and increasingly solar photovoltaic panels and battery storage, which are becoming standard on new dwellings under the coming energy standards. Each of these interacts with the structure and the architecture — where plant and cylinders go, how services are routed through floors and walls, where the panels sit on the roof — and coordinating them early avoids the clashes and compromises that plague poorly planned builds.

Because Crown coordinates the building services alongside the architecture and structure, the new dwelling is designed as one integrated system from the outset. That means the plant has a proper home, the services routes are planned rather than improvised, the roof is designed to take its panels, and the whole house works together to deliver comfort and efficiency. It also means the energy strategy for Part L and the Future Homes Standard — discussed next — is baked into the design rather than reverse-engineered to scrape a pass.

A brand-new dwelling has to meet the full force of the current energy and carbon requirements, and these have changed dramatically in recent years. For a rebuild this is a major design driver, not a box-ticking afterthought, because the fabric, the heating and the on-site generation all have to work together to hit the target — and retrofitting a shortfall late in the design is expensive and disruptive. Getting the energy strategy right from the first sketch is one of the strongest arguments for designing architecture, structure, services and energy as a single package.

The framework is Part L of the Building Regulations (conservation of fuel and power), demonstrated for a new dwelling through the SAP methodology (the Standard Assessment Procedure), which calculates the home's energy performance and carbon emissions against a target. The 2021 uplift to Part L, which came into force in June 2022, raised the bar substantially — requiring around a 30 per cent reduction in carbon emissions compared with the previous standard — and was explicitly a stepping stone towards a bigger change to come. A new home designed today has to be modelled and built to meet that current standard, with the SAP calculation forming part of the Building Regulations submission.

That bigger change is the Future Homes Standard, expected to come into force in 2025. It is designed to make new homes 'zero-carbon ready' — producing around 75 to 80 per cent lower carbon emissions than a home built to the previous 2013 standard — by combining high fabric performance with low-carbon heating (heat pumps rather than gas boilers) and, in most cases, solar panels. In practice this means a new dwelling designed now should be planned around a low-carbon heating system, a well-insulated and airtight fabric, good ventilation and on-site renewable generation, so that it meets or anticipates the Future Homes Standard rather than being caught out by it. Designing to gas-boiler assumptions on a rebuild starting now is a false economy.

We design the fabric, the heating and the generation together to hit the required standard efficiently — insulation levels and airtightness, glazing and orientation, the heat-pump and ventilation strategy, and solar provision — and we build the SAP calculation into the design so the energy performance is designed in, not scrambled at the end. The result is a new Bexley home that is genuinely comfortable and cheap to run, meets the current Building Regulations, and is ready for the Future Homes Standard — which is exactly what a new dwelling should be.

A whole new dwelling needs its drainage designed properly, and on a rebuild this is more involved than people expect. You are dealing with both foul drainage (from bathrooms, kitchens and WCs) and surface-water drainage (rainwater from roofs and hard surfaces), and both have to be designed to work, to connect appropriately, and to meet the council's and the water authority's expectations. Assuming the new house can simply reuse the old drains is a common and risky shortcut — the old house's drainage may be inadequate, poorly located or in the wrong place for the new footprint.

Surface water is where policy has tightened most. Sustainable drainage systems (SuDS) are now expected on new development to manage rainwater close to where it falls and to reduce the rate at which it runs off into the sewers and watercourses — through measures such as permeable paving, soakaways, rainwater harvesting, attenuation storage and green roofs. The London Plan sets out a 'drainage hierarchy' that prioritises these sustainable options over simply piping rainwater to the public sewer. On a rebuild, replacing an old house's hard surfaces with a well-designed SuDS strategy can genuinely improve on what was there, and it is increasingly something the council will look for.

Flood risk is a live issue in parts of Bexley. The north of the borough lies near the Thames and its tributaries, and some areas fall within higher flood-risk zones where a new dwelling has to be designed with flood resilience in mind — floor levels, resilient construction, and sometimes a flood risk assessment as part of the application. Establishing the flood-zone position of your plot at feasibility is essential, because it can affect the design of the new house and the documents the application needs. Even outside the higher-risk zones, surface-water flooding and drainage capacity are relevant and worth checking.

We design the foul and surface-water drainage for the new dwelling as part of the coordinated package, incorporate a SuDS strategy appropriate to the plot, and check the flood-risk position early so any resilience measures or assessments are built into the design and the application. A drainage strategy that is designed rather than assumed is one less reason for the council to hesitate — and one less problem to discover on site.

The 'knock down' half of a knock-down-and-rebuild is a project in its own right, with its own legal controls, and it has to be handled properly rather than treated as a preliminary to the real work. Even where you have planning permission for the new dwelling, the demolition of the existing house usually needs a separate 'prior notification' to the council under the demolition permitted development right: you notify the council of your intention to demolish and provide details of the demolition method and any restoration of the site, and the council has a short period — commonly around 28 days — to decide whether it needs to approve those details before demolition can begin. In a conservation area, demolition is controlled more tightly, and the demolition of a building that contributes to the area's character can require its own consent.

Demolition is also a health-and-safety and environmental exercise. A safe demolition has to deal with the disconnection of services, the safe removal of any asbestos or other hazardous materials (which requires a survey and licensed removal where present), dust and noise control, protection of neighbouring properties and the public, and the responsible disposal or recycling of the resulting material. On most projects the demolition and construction together fall under the Construction (Design and Management) Regulations, which place duties on those who commission and design the work as well as those who carry it out. A competent demolition contractor working to a proper method statement is essential.

Party-wall obligations are the other neighbour-facing dimension, and they are frequently underestimated on rebuilds. Where you are demolishing a house that shares a party wall with a neighbour — a semi-detached or terraced house — or where you will be excavating for new foundations close to a neighbour's building, the Party Wall etc. Act 1996 is likely to apply. That means serving the correct notices on affected neighbours before work starts, and, if they do not consent, following the Act's procedure — usually the appointment of a party-wall surveyor (or an agreed surveyor) to produce an award that regulates how the work is done and protects both sides. This is a legal process separate from planning, and starting it in good time is important because it can take weeks.

We plan the demolition and the party-wall process as part of the overall project programme, so the notification, the party-wall notices, the safety documentation and the construction all sequence together. Handling these correctly is not just a legal necessity; it protects your relationship with neighbours, avoids disputes and delays, and keeps a rebuild — which is inevitably disruptive to those next door — as smooth and neighbourly as it can be.

The Community Infrastructure Levy (CIL) is a charge on new floorspace that funds the infrastructure needed to support development, and it is one of the most important — and most misunderstood — costs of a knock-down-and-rebuild. Unlike an extension, which is often small enough to escape the charge, a new dwelling can be substantial, and CIL is charged on the net additional internal floorspace the development creates. Understanding how it is calculated, and where the reliefs apply, can make a real difference to the economics of a rebuild.

In Bexley two CIL charges apply. The first is the borough's own CIL, adopted under its charging schedule, which sets residential rates by zone: the borough is split by the railway line, with Zone 1 (north of the railway) charged at £40 per square metre and Zone 2 (south of the railway) charged at £60 per square metre. The second is the Mayor of London's CIL — MCIL2 — which funds the Elizabeth line (Crossrail); Bexley falls within the Mayor's lowest band (Band 3) at £25 per square metre, in force since 1 April 2019. Both charges are index-linked, so the actual rates applied are the base rates adjusted for construction-cost inflation to the year of the permission. Both are payable on qualifying new floorspace.

The crucial point for a rebuild is that CIL is charged on the net additional floorspace — the new floor area minus a deduction for the floorspace being demolished, provided the demolished building was in lawful use. In broad terms, if you demolish a house and build a new one, you can offset the floorspace of the old house against the floorspace of the new one, so CIL is charged only on the increase. A like-for-like rebuild of the same size may therefore generate little or no CIL, while a much larger replacement is charged on the extra floorspace. There are conditions — notably that the building being demolished must have been in lawful use for a required period — so it is important to establish the position for your specific building.

Two reliefs matter especially on rebuilds. The self-build exemption allows someone who is building their own home to live in, and who commits to occupying it as their principal residence for a required period (currently three years), to apply to have the CIL exempted — a significant saving on a self-built replacement dwelling, but one that depends on following the exact procedure: applying for and being granted the exemption before starting work, submitting a commencement notice at the right time, and providing the required evidence afterwards. Miss a step and the exemption can be lost and the full charge become payable. The reliefs and the demolition offset are valuable but procedural, and we help you get the CIL forms — assumption of liability, exemption claim, commencement notice — right and on time, because CIL is unforgiving of missed deadlines.

Planning permission decides whether you can build the replacement dwelling and what it looks like; the Building Regulations decide that it is safe, healthy, warm and sound as an actual building. A new dwelling has to meet the full set of Building Regulations from the ground up, which is far more extensive than the regulations that apply to an extension, and building control approval is a separate process from planning that runs through design and construction.

The regulations cover the whole building: structure (Part A); fire safety, including means of escape and the spread of fire (Part B); site preparation and resistance to moisture, including contamination and damp (Part C); toxic substances (Part D); resistance to sound (Part E); ventilation (Part F); sanitation, hot water safety and water efficiency (Part G); drainage and waste disposal (Part H); conservation of fuel and power, i.e. energy (Part L); protection from falling and impact (Part K); access to and use of buildings (Part M); electrical safety (Part P); overheating (Part O); and infrastructure for electric vehicle charging (Part S), among others. A new dwelling has to satisfy all of the relevant parts, evidenced through drawings, calculations and, during construction, inspections.

Because so many of these requirements interact with the design — the structure, the fire strategy, the sound separation, the energy performance, the ventilation, the accessibility, the drainage — the cleanest way to deliver a rebuild is to design with the Building Regulations in mind from the start, rather than obtaining planning permission and then discovering that the design needs significant changes to comply. That is exactly how a coordinated architecture-structure-services practice works: the planning design is already Building-Regulations-aware, so the transition from consent to construction information is smooth.

We prepare the Building Regulations package — the detailed construction drawings, the structural calculations, the SAP energy assessment and the specifications — and coordinate the building control process, whether through the local authority building control service or an approved inspector. That means the same team that won the planning permission carries the design through to the information your builder needs on site, with the regulations satisfied by design rather than by afterthought.

A knock-down-and-rebuild is a full architectural project, and we deliver it through the recognised design stages — broadly following the RIBA Plan of Work — so the information develops logically from first idea to finished home. Understanding what is produced at each stage helps you see where your project is and what you are paying for.

At feasibility (the early stages) we survey the site and the existing house, establish the planning and constraints position — Green Belt, conservation area, flood risk, ground conditions, CIL zone — and develop initial design options, testing what the plot and the policies can support and comparing a rebuild with the alternative of extending where that is a live question. This is where you get an honest view of the project's scale, feasibility and rough cost before committing to a full design.

For the planning application we prepare the full package: an accurate measured survey and existing drawings of the house to be demolished; the proposed drawings for the new dwelling — floor plans with room uses and areas annotated, elevations, sections, a roof plan, a site plan and a location plan — showing the new home's footprint, height, materials, amenity space, parking, cycle and refuse storage, and its relationship to neighbours and the building line. Alongside the drawings we prepare the supporting documents: a design and access statement setting out how the design responds to Bexley's Local Plan and Design Guide; and, depending on the site, a heritage statement (in or near a conservation area), a flood risk assessment, an arboricultural report where trees are affected, a drainage and SuDS strategy, and any other assessments the plot calls for.

Once permission is granted we prepare the technical and construction information: the detailed construction drawings, structural calculations, the SAP energy assessment, the drainage design, the services coordination and the specifications that make up the Building Regulations submission and the package your builder tenders and builds from. We can also prepare the demolition notification and the information for the party-wall process. Everything is prepared to be internally consistent — the floor areas on the plans match the CIL calculation, the structure matches the architecture, the energy strategy matches the services — so a coordinated, self-consistent set of information carries the project from consent to completion.

The process starts with feasibility. We survey the site and the existing house, confirm the planning history and constraints, establish the Green Belt, conservation-area, flood-risk and CIL position, check the ground conditions, and develop design options that test what the plot can realistically support. This is where we give you an honest view of whether a rebuild is the right project and at what scale, before you spend money on a full application.

Bexley offers pre-application advice, and on a rebuild it can be worthwhile — particularly where the design pushes the size or height beyond the existing house, where the plot is in the Green Belt or a conservation area, or where the scheme involves additional units on garden or backland. A written steer from the council on the principle and the scale of your proposal can significantly reduce the risk of a refusal and shows the eventual case officer that the scheme has been developed thoughtfully. We prepare and manage the pre-application submission where it adds value.

We then prepare the full drawing package and supporting statements, submit the application to Bexley through the Planning Portal, and manage it through validation and determination — responding to the case officer's queries, providing additional information, and negotiating amendments where that will secure approval. A single new dwelling is normally decided against the standard eight-week target from validation, though a more complex or contentious scheme — larger, in a sensitive location, or attracting objections — can take longer. Once permission is granted, we deal with any conditions and move the project into the Building Regulations and construction information.

In parallel with the planning and building-regs processes, we handle the rebuild-specific steps: the CIL forms (assumption of liability, any exemption claim such as self-build, and the commencement notice, all in the correct order and at the right time); the demolition prior notification; and the party-wall notices and process. Coordinating all of these together — planning, building control, CIL and demolition — is exactly what stops a rebuild from stalling in the gaps between different processes, and it is a large part of the value of having one team run the whole project.

Understanding why replacement-dwelling applications fail is the best way to make sure yours does not. The most common reason is design and character: a new house that is too big, too tall, too bulky or out of keeping with its street — pushing forward of the building line, dominating its neighbours, or adopting a form and materials that jar with the established character. Bexley's suburban streets have a rhythm and a scale, and a rebuild that ignores them is vulnerable under Policies DP11 and DP12 however good the home is on the inside.

Harm to neighbours' amenity is the second big theme. A taller or deeper new house, or one with windows in new positions, can cause overlooking, loss of privacy, overshadowing or loss of outlook for adjoining properties in ways the old house did not. Where the new dwelling would materially harm a neighbour's daylight, sunlight, privacy or outlook, that is a strong ground for refusal — and one that careful design of heights, roof forms, window positions and separation distances can usually avoid.

In the Green Belt, the decisive reason is size: a replacement that is materially larger than the building it replaces, or that harms the openness and character of the Green Belt, will be refused as inappropriate development unless very special circumstances are shown. On garden and backland plots, over-development is the common failing — too many units, cramped layouts, poor access, or the loss of the spacious green character the council is trying to protect under Policy DP2. And across all rebuilds, unresolved technical issues — flood risk, drainage, trees, or a failure to meet residential space and quality standards — can lead to refusal where the council is left without the information or the quality it needs.

Our approach is to anticipate every one of these reasons and answer it in the application itself. We design the new house to sit well in its street and to treat its neighbours fairly; we keep a Green Belt replacement within what policy allows; we test any additional units honestly against what the plot can carry; and we resolve the technical issues and meet the standards before submission. Where an aspiration simply cannot be reconciled with the policies — a much larger house in the Green Belt, or too many units on a tight plot — we tell you at feasibility, because there is no value in an application designed to fail.

The cost of a Bexley knock-down-and-rebuild has several distinct elements, and it helps to separate them. There is the cost of the design and consultancy — our fees for the architecture, structure and services, plus any specialist reports the site needs; the statutory costs — the planning application fee, the CIL charge on any net additional floorspace, and building control fees; the demolition cost; and the construction cost of the new dwelling itself, which is by far the largest and depends on the size, specification and complexity of the home. We scope our part of the work to your specific project and give you a clear, fixed fee before any drawing work begins.

On the statutory side, the planning application fee for a new dwelling is set nationally and payable to Bexley on submission. CIL is the item most specific to a rebuild: as explained above, it is charged on the net additional floorspace at Bexley's zoned rates (£40 per square metre in the north, £60 in the south) plus the Mayor's MCIL2 at £25 per square metre, both index-linked, with the demolition of the existing lawful house offset against the new floorspace and reliefs such as the self-build exemption available where you qualify. Getting the CIL position and the exemption procedure right can save a substantial sum, which is why we build it into the project from the start.

On timescales, feasibility and the initial design typically take a few weeks once we can survey the site; the planning application runs against the standard eight-week target from validation for a single dwelling, longer for complex or contested schemes; the Building Regulations and construction information follow once permission is granted; and demolition and construction then run according to the build programme, which for a whole new house is naturally a matter of many months. We give you a realistic programme for your specific project at the outset, and we sequence the planning, CIL, demolition and party-wall steps so they do not become bottlenecks.

It is worth remembering that money is not lost on good design, proper engineering and a well-prepared application — it is lost on refusals, on abortive schemes that were never going to pass, on demolishing a house before the rebuild has consent, on foundations that have to be redesigned because the ground was not investigated, and on energy shortfalls discovered too late to fix cheaply. Getting the rebuild right first time — designed as a coordinated whole, with the planning, structure, services, energy and CIL all worked out — is the most cost-effective way to turn a tired Bexley house into an excellent new home.

To make the process concrete, consider a common Bexley scenario: a tired 1930s detached house on a generous plot in a leafy Sidcup avenue, with small, dated rooms, poor insulation, a cramped kitchen and no realistic route to the modern family home its owners want. Extending has been considered, but the layout is so compromised, and the fabric so poor, that a comprehensive new house would deliver a far better result. The owners want to knock it down and rebuild a larger, highly efficient four-bedroom family home, and they intend to live in it themselves.

At feasibility we check the fundamentals: the plot is not in the Green Belt or a conservation area; it lies in flood zone 1 with low flood risk; the ground is London Clay with mature trees nearby, which will drive the foundation design; and it sits in the borough's southern CIL zone. We survey the house and the plot and test a design that respects the avenue's building line, height and spacing while giving the owners the space they want — checking every room against the space standard and designing the new house to sit comfortably between its neighbours without overlooking or overshadowing them. Because the owners will build and occupy the home themselves, we flag the CIL self-build exemption immediately and plan to secure it before any work starts.

The engineering and services are designed alongside the architecture. The clay soil and nearby trees point to deeper foundations detailed to resist shrinkage and heave; the open-plan ground floor and large rear glazing are engineered with the necessary beams and load paths; and the fabric, an air-source heat pump with underfloor heating, mechanical ventilation with heat recovery, and roof-mounted solar panels are designed together to meet Part L and to anticipate the Future Homes Standard, with the SAP calculation built into the design. A SuDS strategy — permeable paving and a soakaway — manages surface water better than the old house's hard drive ever did, and the foul and surface-water drainage is designed rather than assumed.

On the planning side we prepare existing and proposed drawings with every room's floor area annotated, a design and access statement showing how the new house answers Policies DP1, DP11 and DP12 and the Design Guide, an arboricultural report for the trees, and a drainage strategy. We calculate the CIL, offsetting the demolished house against the new floorspace so the charge falls only on the increase, and prepare the self-build exemption claim to remove even that where the owners qualify. Submitted through the Planning Portal and managed through Bexley's validation and determination, the application goes in as a proposal the case officer can recommend for approval — a well-designed new home that respects its street, protects its neighbours and meets every standard.

Once permission and any conditions are dealt with, we submit the demolition prior notification, serve the party-wall notices, complete the CIL forms in the correct order (assumption of liability, self-build exemption, and the commencement notice at the right time), and prepare the Building Regulations and construction package. The same coordinated team that won the permission carries the design through to the information the builder needs, the old house comes down safely, and the new home goes up as drawn. That is the difference between a rebuild designed to succeed and one simply hoped through.

Crown Architecture designs replacement dwellings across Bexley and the surrounding boroughs, and we do it as a single coordinated service: the planning design, the structural design and the building services under one roof. That matters more on a rebuild than on almost any other project, because a new dwelling is engineered in its entirety — foundations, frame, services, energy and drainage all have to work together — and designing them separately produces clashes, compromises and costly surprises on site. Designed together, the home you get consent for is the home that gets built.

We know what decides a rebuild in Bexley: the fact that a replacement dwelling is a new building needing full planning permission; the Local Plan policies on design, character, density and residential quality; the Green Belt and garden-land constraints where they apply; the space, energy and Building Regulations standards a new home must meet; and the specific mechanics of CIL, the demolition offset and the self-build exemption. We use that knowledge to give you honest advice at feasibility — including whether a rebuild is genuinely the right project rather than a major extension — and to prepare applications designed to pass rather than to hope.

Just as importantly, we are straightforward to work with. We tell you early whether a rebuild stacks up and at what scale, we quote a clear fixed fee, and we prepare a coordinated, self-consistent package — drawings, design and access statement, structural and services design, energy strategy, drainage, and the CIL and demolition paperwork — that a case officer can approve without having to fill gaps. Then, once permission is granted, we carry the scheme through the Building Regulations, the CIL and party-wall steps and the construction information your builder needs.

We also stay with the project after the drawings are done. We manage the application through Bexley's validation and determination, respond to the case officer, negotiate amendments where that will secure approval, and — once permission is granted — help discharge conditions, get the CIL forms right and on time, handle the demolition notification and party-wall process, and prepare the construction information. The aim is a single, accountable point of contact from the first survey to a finished, mortgageable new home, rather than a set of drawings handed over and a client left to navigate the council, the levy and the demolition alone.

If you are considering knocking down and rebuilding in Bexley — whether you already own the house or are weighing up a purchase — send us the address and what you have in mind, and we will tell you honestly what is achievable, whether a rebuild or an extension serves you better, and how to get there.