Extend your home with a basement conversion - whether you want a new bedroom, office, playroom or even a home cinema or gym, converting your basement is a great way to add space to your home.
How much does a Basement Conversion cost?
Average cost in UK: £1216
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The average cost for a basement conversion is £1216. You are likely to spend between £750 and £10000 total. Exact price may vary depending on your area and project details.
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Whether you want a new bedroom, office, playroom or even a home cinema or gym, converting your basement is a great way to add space to your home.

Waterproofing your basement

People tend to think of cellars as cold, damp and dingy, but new waterproofing techniques prevent these problems from developing. “We use a cavity drainage system which is relatively easy to put it and is a standard form of waterproofing basements,” explains John, “It’s a pump system which gets rid of any water which drains down into the walls.”

This damp proofing solution works by leaving a gap between the wall and a waterproof membrane, which allows any excess water to drain down the gap and be pumped out. Put simply, specialis says: “You can think of the basement like a fish tank – it’s sealed so no water can get out but also none can get in.”

Why convert your basement?

According to the Wisetradesmen Survey, one in ten people questioned had added space to their home in the last 12 months.

Basement conversions are often less intrusive alternatives to loft conversions or extensions. John White, who works for one of basement conversion company in Bristol, points out that: “Basement conversions have become more popular recently. If the basement is already formed then it tends to be a lot cheaper than converting a loft or adding an extension.”

Not only is having a basement conversion a good alternative to moving, it can increase the value of your home.  A basement conversion specialist says that the amount it costs to convert a cellar is normally equal to the value it can add to your home; “Depending on where you live and the types of houses in that area,” he adds.

What can you use a basement conversion for?

Basement conversions can be used to create almost any kind of space: a utility room, playroom, kitchen, office, or even a pool, gym or spa. “Our average customer lives in a terraced house and will usually want the basement converted as an extra bedroom,” specialist explains.

If you already have a basement then converting is a likely option. If you don’t, one can be dug out but the process is painstaking and very expensive. “There is a market for dug out basements in places like Chelsea, on big value properties where the customer wants a swimming pool or gym.”

Things to consider

Your new basement could be used as an office, playroom, or even a home cinema

Basement lighting - lighting your basement conversion is key to making sure that the space is appealing. Good use of spot lights throughout the room is one way of achieving this but you can make use of natural light as well. Light wells allow sunlight to flow through into the basement or you could dig down into your garden to put in windows.

Heating and ventilation - as specialist explains, heating and ventilating a basement is relatively simple: “Radiators can be put in and linked up to your main central heating system easily and you can use extractor fans to ventilate.”

Plumbing - plumbing can be put in to allow for an extra bathroom in a basement conversion. Even if there is no existing drainage there, a pump system can be used to get rid of waste.

Planning permission for basement conversions and party wall agreements

Basement conversions rarely require planning permission, but a specialist will be able to advise you on this. Basement expert John points out: “You will normally need permission if the building is listed or you are digging out a new basement.”

If you share walls with your neighbours you will need to draw up a party wall agreement. If you’re having any kind of building work done it is always best to talk to your neighbours about it first.

Building regulations for basement conversions

As with any home improvement work, you need to ensure that you comply with current building regulations. The best way to do this is to hire professional contractors or use a basement conversion company. The regulations concern all areas including wiring, insulation and fire regulations. It is important to update your home insurance to include the basement conversion.

How much does a basement conversion cost?

You should consult a basement conversion specialist who will normally offer a free survey and a quote for the work up front. Specialis suggests that: “It’s important to have a budget and I would say you’d need to have at least £10,000 for a basement conversion.” John quotes the average cost of an existing basement conversion at around £15,000. He adds: “Two years ago we dug out a new 40ft square basement in Bristol which cost £29,000.”

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