Cellar conversions Do's and dont's

Converting an existing cellar into a habitable room is a way of extending a home without reducing the size of the garden and avoiding the hassle and cost of moving house. Popular uses for converted cellar space include, home office, or study room, playroom for the children, home cinema, hobby room, spare bedroom, even an additional lounge or utility room.

The work normally falls into three stages :-


1. Structural works (demolition of partition walls, digging down to create additional headroom)

2. Waterproofing and

3. Finishing works such as plastering and joinery, electrical and plumbing works.



The basis of a successful project is getting the waterproofing system right, if this fails everything gets ruined. The industry has seem much innovation in recent years and there is a useful document 'a Guide to Waterproofing existing basements' by Raymond Foulkes - published by the British Structural Waterproofing Association. The rest requires no more than traditional building skills. Be aware though, if more headroom is required, the existing foundations may require underpinning, this can be an expensive and time consuming part of the projects as it involves heavy manual work, basically putting additional concrete underneath the existing foundations - one bit at a time.

The concept of cellar conversions is one that has grown in popularity over recent years, especially with the increases in stamp duty, the requirements for home buyer packs and other obstacles that the government has put in the way of moving house. Add to this the recent difficulties of finding a buyer and obtaining a new mortgage and the idea becomes even more attractive. For many people, the need for more space is real but they like their existing home, they have put work and love into making it what they want and simply do not want to move. They may have already converted the loft and the only way now is to go down!
The more complex and expensive projects involving underpinning are more common in areas where real estate values are high, many parts of London and other up market neighborhoods in cities around the country, Leeds and Manchester in particular. However if we take into account the cost saved in not moving house it can make sense even if the added value is less than the cost of the conversion, so there has been a growth in this type of project in most parts of the UK in recent years.

So when is the best time to undertake such a project? Well, before you actually need the space is advisable. Don't wait for that baby or elderly relative to arrive, before you start the work! You may find that you have to give up some living space on a temporary basis to facilitate the work itself. Now is a good time as most specialist companies have cut their prices due to the recession and there are some bargains to be had, but this won't last forever and prices will rise again as soon as we start to come out of recession.


Do's and Dont's of Cellar Conversions

Do employ a true specialist for the water-proofing.

Do not rely on advice from your builder, friend or even architect when it comes to designing the waterproofing!

Do read the various guides that are in print so that you can evaluate the various opinions that you may encounter.
Do not employ a firm that has not heard of the British Standard BS8102, the BSWA Design Guide 'Waterproofing Existing Basements' and the NHBC publication 'Basements for Dwellings'

Do make sure that you have a sump and pump include in your system, even if your cellar has not history of flooding (yet)

Do not choose your basement waterproofing system based on price alone, you may live to regret it and find it is not the cheapest in the long run!

Do make sure that you comply with Local Authority building control, party wall legislation (if applicable) and obtain any necessary planning consent, especially if you intend to sell our property with the converted cellar as part of the living space.

Do not lower the floor without at first taking the advice of a structural engineer - you may require underpinning!

Do read the terms and conditions of contract carefully, whilst it is normal to allow a contingency for unforeseen items try to make sure that most things are included rather than excluded by the terms and conditions.

Do not let the 'lowest price' seduce you into signing a contract that may prove to have a higher final bill than you thought.

Do make sure that you take up references and even go to see finished work of the firm that you intend to employ.

Do not be fooled by a slick sales presentation and glossy brochures alone.

Do ensure that you include adequate natural light, ventilation and a secondary means of escape.

Do not leave moving of gas and electrical services to the last minute, it can take months to organize this!

Do choose a firm that offers an on-going after sales service.

Do not be put off at the thought of maintaining a pump; cars, washing machines and central heating systems all need maintenance and that is not normally considered to be a problem. A waterproofing system that cannot be repaired or maintained CAN be a problem!

Do keep your neighbours informed and on your side, and plan the works with consideration for others, cellar conversions can be be disruptive at the best of times!

Ask the author a question about your cellar conversion.

Ray Foulkes has served several years as technical officer for the British Structural Waterproofing Association and is author of the design guide 'Waterproofing Existing Basements'
Through his group of companies he offers a full design and installation service as well as a unique range of products for DIY installation.

He pioneered the use of proprietary underfloor channeling systems and the use of thermally insulated membranes for basement waterproofing and imports products from around the world for this purpose including the Grate range of basement waterproofing systems