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Initial things to consider when converting a basement.

The media has recently been littered with stories of very controversial super- basement conversions. The homeowners love them and the neighbours hate them. There is no one in the middle. As they are forever making headlines, we assess the pros and cons of extending a properties square footage by digging down.

London is now swarming with basement conversions and has been for the last few years. It now seems that this trend for building down has spread to beyond the M25. Perhaps initially used a recession defying alternative to create more space as opposed to up sizing, basement conversions and extensions seem to be the most popular option for creating more square footage but also adding great value to your home.

Why build up when you can build down?

Experts have been quoted as estimating that by spending £300 per square foot on building a basement, you can expect to yield as much as £2,000 per square foot at the point of sale. With that rate of yield, and space at a premium, it’s easy to see why basement excavations are becoming so popular. However, basement extensions have not been met with universal support, with many high profile local residents protesting against the rise of the ‘iceberg homes’ and the constant disruption they cause . It is not only the disruption to your neighbours that you must consider when you decide to expand downwards. Below are some of the things you should consider when doing any substantial work to your house, but with a particular focus on basement works.

Planning permission

If you are converting an existing cellar into a habitable basement space, you may not require planning permission, as your conversion will simply involve a change of use. Similarly, some basement works are covered by permitted development rights. However, if you are creating a new basement which involves major works, a separate unit of accommodation and/or alters the external appearance of the property, e.g. adding a light well, you are more likely to require planning permission.

It would be recommended that you or your architect contacts the local authority before you start work for guidance on whether you will require permission. If you do not require permission, it may be worth requesting written confirmation of this, as this will be useful when you come to sell the property on. You should remember that you may also require other permissions, such as from the freeholder, or estate holder. If you live in a listed building you are likely to need consent for any works done.

Those that live in listed buildings or within conservation areas will have even more hurdles to climb. Listing buildings and conservation area are buildings or areas of special architectural or historic interest, the character or appearance of which it is desirable to preserve or enhance. As such, these building and areas have extra planning controls and there is less permitted development as a result.

Building control

Even if planning permission is not required, if you are creating a new habitable space at your property, Building Regulations approval will be required. Building Regulations are separate from planning permission, and provide statutory minimum construction standards to ensure that buildings are safe, hygienic and energy efficient. If you are looking to sell the property on once the works are finished any prospective purchasers will want to see a copy of the Building Regulation Completion Certificate. If you do not obtain one, you may be asked to cover the cost of an indemnity policy for the purchaser, or in worst case scenarios, a sale may fall through due to the lack of building regulations approval, with a lender refusing to advance monies on a basement which has not been signed off as structurally safe.