Knocking down and rebuilding a house: replacement dwellings explained

Sometimes the best thing about a house is the plot it's standing on. A good-sized garden, a quiet road, a view, and a house that's tired, poorly built or simply the wrong shape for how people live now.

That's when the idea of knocking it down and starting again comes up. It's a bigger decision than an extension, with its own planning, tax and practical issues. This is a builder's summary of how it tends to work, not planning or tax advice, and the specifics depend on your council and your circumstances.

Why rebuild rather than extend

Sometimes the existing house simply isn't worth keeping. The structure is poor, the layout can't be fixed without moving most of the walls, or bringing an old house anywhere near new-build standards of insulation and airtightness would mean rebuilding most of it anyway.

The numbers can be closer than people expect. On our published 2026 rates, excluding VAT, a whole-house refurbishment runs at £1,400 to £2,800 per sq m, and new floor area added as an extension at £2,400 to £3,600 per sq m. A new house built to a good standard is £2,000 to £2,600 per sq m, with demolition and clearance on top. Those ranges overlap, and on a house that needs everything doing, a rebuild can come out close to a deep remodel before you even look at VAT.

The other side deserves a fair hearing. Our Wilmslow house was a 1930s detached that we extended front and rear and completely re-serviced, keeping the house rather than replacing it. Keeping a house avoids demolition, keeps whatever character it has, and is often a simpler planning conversation. The right answer depends on the house, not on a rule.

How planners look at a replacement

A replacement house needs planning permission. The council will look at it much as it would any new house: its size and height, where it sits on the plot, its design and materials, and its effect on neighbours through overlooking, loss of light or sheer bulk. A replacement that's noticeably bigger than the house it replaces will get the closest attention.

A few things often come up:

• Bats. Older houses, particularly their roof spaces, can be home to bats, which are protected. A survey is usually needed before demolition, and some surveys can only be carried out at certain times of year, so start early.
• Conservation areas. Demolishing a house in a conservation area generally needs planning permission in its own right, and the council will want to understand why the existing building doesn't contribute to the area.
• Trees. A bigger footprint, or a new position on the plot, can bring the house closer to protected trees.

Most councils offer pre-application advice for a fee. On a replacement dwelling, especially a larger one, it's usually money well spent.

Green Belt: the size question

Much of the countryside around Wilmslow, Knutsford, Prestbury and Alderley Edge is Green Belt, and there the size of the new house becomes the central question.

National planning policy treats replacing a building in the Green Belt as acceptable in principle, provided the new building is in the same use and not materially larger than the one it replaces. What counts as materially larger is a judgement, and councils set out their own approach in their local plans. Floor area matters, but so do height, volume and how the bulk is spread across the site.

In the Green Belt, the house you're allowed to build is measured against the house that's already there. Don't knock that one down until you know what replaces it.

That's meant literally. Don't demolish the existing house before you have permission for the new one, and talk to your planning consultant before removing outbuildings or extensions, in case they matter to the comparison. Permitted development rights are often removed from the new house by condition, so later extensions may need a planning application.

VAT, CIL and the practical side

VAT. Where the old house is demolished completely to ground level and a new one is built, the work is generally treated as building a new dwelling, which a VAT-registered builder can zero-rate. If part of the old house is kept standing, the project may instead be treated as alteration or extension, which carries the standard 20 per cent, though there are narrow exceptions. HMRC's VAT Notice 708 sets out the rules. Get your accountant's view before your design keeps any part of the old structure.

CIL. Where the council charges the Community Infrastructure Levy, a replacement can be liable on the extra floor space. Existing floor space that has been lawfully in use can usually be offset, and a self-build exemption may be available. Either way, the forms need to be in before work starts.

Demolition. An asbestos survey is needed before demolition, the services have to be disconnected safely, and the council needs formal notice of a demolition under the Building Act, which is separate from planning. If the house is attached to a neighbour's, the Party Wall Act will apply.

Living elsewhere. Unlike most extensions, a rebuild means moving out for the whole build. Rent or temporary accommodation belongs in the budget.

Where to start

Send us the address, some photographs and anything you have on the planning history. You'll get a straight answer from the person who would run the job on what a rebuild costs compared with refurbishing and extending, and on who you'll need on the planning side. More about our one-off homes is on our new build homes in Cheshire page, and the costs that sit around the build rate are covered in what it costs to build a house in Cheshire.