Converting and extending a basement can provide extra living space without drastically altering the exterior of your home.

People these days are all wanting more space their home. Unlike loft space at the top of the house, which tends to be best for creating additional bedrooms, a basement is located close to the main living areas and access, and has a more flexibility for its use. A basement is the ideal location for additional family living space, such as a playroom or home entertainment room. It is also a great place to relocate the utility room, boiler and storage.Alternatively, a basement can have its own external entrance and provide a self-contained unit, ideal for use as a home office, annexe, etc.

 

Planning Permission

Converting an existing basement beneath a dwelling from a storage area to habitable space involves only a ‘change of use’ and so does not require planning permission. Reducing the floor level of a cellar to improve the ceiling height will enlarge the volume of the property, however this may need running past planning.

For more information visit www.planningportal.gov.uk.

 

Building Regulations

The creation of a new habitable basement will require Building Regulations approval regardless of whether it involves a change of use of an existing cellar, or the creation of a new or larger basement through excavation.

The Building Regulations are statutory minimum construction standards that ensure buildings are safe, hygienic and energy efficient.

For guidance on meeting the Building Regulations, get a copy of the Approved Document — Basements for Dwellings, which includes all of the relevant regulations.

 

Tanking Waterproofing below ground level is often referred to as tanking’ the application of a layer of waterproof material directly to the structure. This is usually a cementitious waterproof render system on the walls, typically applied in several layers, linked to a waterproof screed on the floor. Tanking can also involve a sheet membrane, asphalt or other liquid-applied waterproofing material. Tanking is also required to withstand the external water pressure around the cellar (hydrostatic pressure). The pressure from the water table around a basement can be enormous and unless the tanking is very securely fixed to the substrate, it can fail. Hydrostatic pressure will force water through the tiniest fault very rapidly and once a leak occurs it can be very difficult to isolate and repair.

Cavity Membranes: Cavity drain membranes are an alternative. The membranes are used to create an inner waterproof structure in the basement or cellar, behind which is a cavity (created by the membranes studded profile) that is fully drained, so any tiny leaks in the outer structure are diverted harmlessly away via a drain. By constantly draining away any small leaks there is never any water pressure against the inner structure. Several reports consider cavity membranes to be the most reliable way to waterproof a basement.