Should You Convert Your Basement?

When extending our homes, most of us would think of building outwards or into the loft. However, by digging down into the cellar or basement, you can create an additional floor running the entire length of your house, and open up a wealth of opportunities for a bigger and better home.

What Type of Home is Suitable?

A basement conversion is particularly suitable for a terraced or semi-detached urban home where adding a conventional extension or going up into the loft isn't possible. Start by getting a specialist company to assess your home's feasibility for conversion. The ideal candidate is a house with an existing cellar or basement - usually built before 1930 - and if headroom is restricted, the floor can be lowered. Even if you don't have a cellar, a retro-fit basement can be built from scratch but as this involves digging out the area by hand it is, not surprisingly, far more expensive and time-consuming. Until recently, new basements could only be built in properties with suspended timber floors, but there are now techniques for constructing them under concrete.

What's Involved?

If you're lowering an existing cellar floor to create more headroom, or building a brand new basement, you'll need to underpin the foundations, which entails extending them downwards for additional support. The basement will then need waterproofing by lining it with a studded membrane, then building a secondary wall inside the lining - regarded as more effective than the previous method of tanking it with a cement lining. Any water that seeps in collects in a sump underneath, and is then pumped away, to keep damp out even in areas where the water table is high.

Who'll Do the Work?

Converting a basement is a highly specialised job and, to get it right, you will need to employ experienced professionals. There are various options - you can get an architect to draw up plans, recommend contractors and oversee the build, or just ask the architect for plans, then choose your own builders and project manage the job yourself. Or you may prefer to hire a basement conversion company to handle the entire project including design, planning applications and kitting it out once complete.

Planning Considerations

If your home is terraced or semi-detached you'll need consent from your neighbours before work can proceed. This will be via a party wall agreement, and you will have to pay for a surveyor to allay any fears about subsidence or damage to shared foundations As with all structural work, you will need buildings regulations consent but won't generally need planning permission unless adding a light well, which will change the building's external appearance, or creating new habitable space. To be on the safe side, always check with your local planning department in case such permission is required.

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