Knock down or rebuild?

When undertaking a large project such as remodelling or the heavy extension of an existing house, the question that often arises is; wouldn’t it be better to knock the lot down and start from scratch? To fully answer that question, involves having a thorough understanding of the red tape, logistics, design and economics that may go with it.

Red Tape

Compared to extending and remodelling, carrying out a new build will add significantly to the administrative and technical requirements needed to satisfy the planners, building inspector and the mortgage company.

An extension or remodelling project will involve a householder planning application, whereas a new house will require a full planning application.  The planners will invariably impose a whole raft of extra hurdles to overcome that wouldn’t have been the case with the simpler householder application.  Depending on the location the extra information required could include flood risk assessments, ecological and biodiversity reports, noise impact assessments, community involvement statements all alongside the mandatory design statement. Bizarrely you may find that the house does not fit with the local authority’s goals as set out in their local plan for new housing, in an urban setting they may consider the site warrants more than one dwelling and / or that your proposal is too large if in the countryside.

Applying Building Regulations to the whole building as opposed to simply the extended or altered areas will invariably result in carrying out or installing features that you hadn’t banked on. Not that these features are bad in themselves, but once the entire building becomes subject to current legislation as opposed to simply say the extension, things can go a little array. For example the house would need to be wheelchair friendly on the ground floor. This might mean that the WC compartment needs to be larger than the one it replaces, or that you couldn’t have a step in the ground floor levels. Building Control will also require the whole property to meet present day energy conservation regulations, this will result in air testing, higher specifications and practices in the build.

Unless the project is financed without a loan and there are no plans to sell the completed property in the next 10 years or so, the house will require a building warranty. Even if the project isn’t financed through a loan it would always be prudent to secure a warranty on the home, so as to be in a position to sell it to someone that might need a mortgage should the need arise. The need for a building warranty will bring about additional controls and measures into the planning and the build process.


Where to live during the build, is usually the greatest logistical problem faced by most people knocking down their home. Whilst moving out can apply to extensions and remodelling, there is no getting away from the fact, that relocating home, at the same time as embarking on a large project is a daunting prospect. Ideally it is best to have a base  close to the site so that you can keep an eye on things and respond to issues that arise.

The additional red tape will result in the project taking longer to commence and when it does finally get off the ground, demolition will mean that the work goes into reverse before it can move forward.  Demolition will require materials to be sorted for recycling, services being disconnected and any adjacent buildings being weatherproofed or even shored up. However, once the existing building has been removed and the site has been turned into a brown field, work should be more straightforward with little need for extras from unforeseen work.

Once demolished, speedier progress can be made on the areas of the property that would have been altered. For example forming a structural opening in an existing wall can take longer than building a new wall and placing a lintel or beam on it.  Material movements in and out of the site will be just under doubled on a total rebuild, which on a small site or one with poor access could be an aggravating factor with neighbours.


The design will play a large factor in whether it is viable to retain the old house or demolish it. If the design necessitates moving every window and door position, knocking down so many walls and removing the roof so that the original house becomes unrecognisable, then you would be right to question whether it is better to demolish the house. This situation becomes clearer when heavily extending a small property to create a very large home. In this case it would probably be wrong to dictate the scale and design of the smaller property on to the larger home.

A remodelling scheme that works well with the existing house will cleverly use the existing scale and shape of the building, whether this is maintaining existing window apertures, or retaining large areas of walls and roof lines, all will help to keep the budget under control. If however a design is imposed on an existing house that is not suitable, either the cost will spiral out of control, or the result will be a bodged design, in that scenario it would be prudent to knock it down and start from scratch.


The big saving on a demolition and rebuild is due to regulations which allow the 20% VAT paid on eligible goods used in the construction to be claimed back at the end of the build. There are a number of rules and restrictions limiting what can and cannot be claimed for, all of which nibble away at the headline saving.

Offset against the VAT saving is the added cost of demolition and works associated with building a modern house. Demolition and disposal of the old house is best contracted to a professional demolition crew which could cost £3,000 to £10,000 depending on the size of the existing property.

Living in a second home, even if that is simply a large caravan onsite will eat into the overall saving, as will the increased bureaucracy and additional work needed to satisfy regulatory requirements.

The new home warranty will add around 1% to the budget for the paperwork. The actual cost of a new home warranty could rise to much more due to the need for the builder to be a paid up registered member of the warranty scheme, which effectively removes a lot of smaller extension builders from the equation.


Totally demolishing what is likely to be your greatest asset to create a brown field site for a new build is by anyone’s standards a scary thing to do. Even with such a bold step the savings are not likely to be the headline 20% which can be claimed back on VAT.

Careful planning and design of a remodelling project that works with rather than against the existing house will keep the budget under control. Only by fully costing and appraising the options of remodelling against demolition and rebuild will the true benefit if there is any, be determined.

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