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Bringing (Half) The House Down: Things To Consider When Planning To Demolish A Semi-Detached Home

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There are many good reasons an individual, family or development company might wish to knock down a building, from the prohibitive costs of renovating older properties to planning permission changes and simple property tax reduction. However, demolishing a building can also be a complicated process to arrange, and it can be particularly complicated if you are knocking down half of a semi-detached, maisonette or duplex house.

Naturally, knocking down half of a free-standing building and expecting the remaining half to remain habitable and structurally stable requires careful planning and effort, and there are a number of pitfalls that can befall the unwary. To help you avoid these pitfalls, keep the following key questions in mind when planning your semi-detached demolition project:

Is the other half of the semi-detached occupied?

Obviously, knocking down half of a semi-detached building is a much more complex endeavour if the other half still plays host to a family, and it goes without saying that you should keep the adjacent occupants as informed and involved as possible while planning and executing your demolition. As well as notifying the occupants of the planned demolition well in advance, you may also have to find them alternative accommodation while the bulk of the work is carried out, particularly if the building contains asbestos or other potentially dangerous materials. 

It is generally a good idea to keep some legal assistance on hand during this process, especially if your soon to be ex-neighbours are less than happy about the planned work. You should also keep your chosen demolition contractor well informed on the situation, to ensure no accidental damage is dealt to the remaining property.

What will you do with the party wall?

The wall that divides the vast majority of semi-detached houses is load-bearing, and is therefore generally strong enough to serve as an exterior wall once your half of the semi has been demolished. However, party walls were not built to endure outdoor exposure, so you will have to make some modifications to it if the remaining part of the building is (or will be) inhabited. Extensive insulation will have to be installed, and you may also have to attach some kind of weatherproof cladding (such as aluminium siding) to the newly exposed wall.

If you are knocking down half of a semi-detached building intending to replace it, you may be able to get away with leaving the party wall unmodified, especially if the new building follows the same dimensions as the old one.

How will the foundations be protected?

Even if the other half of a half-demolished semi is uninhabited, you will still have to take steps to protect the remaining foundations of the building, including those that supported your side of the building. Without protection, water will start to erode the concrete and weaken the foundations of the entire structure, so at the very least any exposed foundations on your side of the building will have to be re-buried. Consult closely with your demolition contractor, someone from a place like JAG Demolition, on this topic, as many are experts at demolishing sections of foundation without harming the rest, therefore giving you less to cover.