Underground conversions are growing in popularity, even through they are often the most expensive conversion of the lot. This is happening more in areas where there is a great deal of pressure on house prices and many of the houses are old stock so are therefore likely to have a cellar or a basement in the first place, such as London and other popular cities.
Cellar or Basement?
So what’s the difference between a cellar and a basement? A basement generally covers the whole of the ground floor, will have a separate entrance, possibly accessible from the outside, and some natural light and ventilation.
This is because in the past they were proper rooms, used as kitchens and sculleries by the servants, and the access allowed tradesmen to visit without disturbing the household.
A cellar is simply a space below ground, probably only under part of the ground floor, with access from inside the house by a staircase or trapdoor and ladder. They were used for storing coal (or other goods) and might therefore have a coal chute leading into the space from the street.
In England and Wales, planning permission is not normally required for the conversion of a cellar or basement into a usable room, unless it entails a change of use, such as turning it into a garage or home office.
Building Regulations approval will be required for any structural work though. In Scotland and Northern Ireland the regulations are different so you’ll need to contact the local planning office to find out what they are.
The Building Regulations cover the standard of materials and construction used in the project and will make sure that the area is safe, specifying fire exits, for example, and adequate lighting, ventilation, damp-proofing and electrical and gas works.
So although this might be considered a bit of a pain, it’s really a vital check to make sure your family will be safe.
Integrating the Garden
A basement is obviously a better bet for conversion than a cellar. Many successful basement conversions concentrate on enhancing access to the garden, for example with a kitchen-cum-family room in the new basement with wide glass doors to the garden.
This frees up the rooms on the ground floor to be used as living space or bedrooms, depending on the demands of the family.
Costing the Earth
Major expense comes from two areas, structural reinforcement and damp proofing. Many Victorian properties have little in the way of foundations and this is often only discovered when the excavation begins, though experts will be expecting it.
Under pinning will then be vital but it can cost thousands so it’s best to get in a specialist builder or under-pinning firm to advise and quote.
As with every other job that you are employing someone to do, get estimates from at least three firms before making your choice.
Holding Back Water
Preventing water from coming in may well be the most difficult part of the project. Rainwater will naturally fall down toward the new room and ground water may well seep up to it. Couple this with the water trying to get in through the walls, particularly if your guttering isn’t in good condition, and you can see that it’s vital to get this right.
The two main ways of tackling the problem are to take the water away with improved drainage and create a barrier to prevent the ingress of water in the first place (known as tanking) and it’s likely that most conversions will use a combination of the two.
In some cases the drainage system will be supplemented with pumps if gravity isn’t going to be enough to do the job. Every situation is likely to be different so expert advice, again from at least three candidates, is critical.
One of the benefits of using the basement is that it’s close to the living areas of the house. So, compared to a loft conversion, for example, the space can be more integrated into family life.
Cellars have been converted into kitchens, dining rooms, playroom, garages and even offices and home cinemas! The only limit is your imagination.