It is very common in northern Europe, especially Scandinavia, to see the semi-basement flat configuration where the window sills are at ground level and this effectively creates an extra story without making the building much taller. Alternately these areas may be used for utility rooms, storage or, if the contours permit, garaging. It is quite a mystery why the cellar, which was so common in traditional UK buildings, particularly in the Georgian, Victorian and Edwardian periods, has not been carried on with and developed into a dry basement. This is particularly strange when you consider the high price of building land and the high demand for storage space. A semi basement area is effectively partly earth sheltered.
One or two of the German timber kit house importers now offer the option of a prefabricated basement room. Glattharr even have a floating show house to prove the waterproof standards of their construction methods!
Another, cheaper approach is the more traditional cellar which is not moisture proofed but can be used for storage provided items are kept dry by wrapping in plastic or whatever, depending on the material. Also useful for storing garden produce and can be used for garaging.
There needs to be some way of making sure that ground water pressure does not force water into the structure. If the water table is constantly low (below the lowest part of the basement floor) then a French drain may be sufficient. The French drain, as it is known, is made by placing a layer (about 300mm wide) of gravel or clean hardcore around the walls of a basement with a land drain at the bottom. The point is that this does not prevent moisture encroaching into the basement walls but it does stop water pressure building up and forcing water in. If there is likely to be a problem with damp then the walls and floor can be lined with cavity[for the purposes of part B of the Approved Documents] - A space enclosed by elements of a building (including a suspended ceiling[for the purposes of part B of the Approved Documents] - A part of a building which encloses and is exposed overhead in a room, protected shaft or circulation space. (The soffit of a rooflight is included as part of the surface of the ceiling, but not the frame. An upstand below a rooflight would be considered as a wall.)) or contained within an element, but not a room, cupboard, circulation space, protected shaft or space within a fluepipe to conduct gas, typically ventilation air or boiler exhaust. see Flue, chute, duct, pipe or conduit. drain membranes or special types of waterproof concrete can be used.
Often the problem with existing basements is dampness in the walls and floor (and maybe from a vaulted ceiling). The way this is handled depends on how serious the damp is and what the space is to be used for. If the area is subject to wet rather than merely damp (ie. standing water or drips from the ceiling or running walls) then not only will the surfaces need totally lining with a special type of heavy grade plastic liner or stainless steel liner but will also require a perimeter drain in the floor with a sump pump to remove the water.
If it is simply a matter of damp surfaces which never become wet then it may be possible to simply line them with a damp proof membrane and some type of insulation and surface board or finish.
First you must establish whether the basement area is damp or wet (or ever gets wet). These are very different situations because damp can be covered over with a damp proof membrane (DPMdamp proof membrane - a sheet of (usually) plastic used to prevent dampness rising up through a floor or in through an underground wall. see more) whereas if water ever drips or runs down the walls or there is standing water on the floor then this must be dealt with by leading the water down behind a studded water proof membrane to a drain and pump in the floor. If you are new to the house try to find out if there has ever been flooding or standing water, possibly in neighbouring house basements.
Secondly you need to decide whether you want an unheated storage area with basic functional surfaces or whether it is to be a heated habitable room.
Damp walls and floor for utility/storage/parking use where there will be no heating
This provides no insulation.
Damp walls and floor for habitable use where there will be heating
There are various thicknesses of expanded polystyrene boards and phenolic boards bonded to plasterboard designed for dry lining walls.
Wet walls and floor for utility/storage/parking
If the walls and floor are wet rather than damp then it is possible to use a system of high density polyethylene (HDPE) cavity drain membranes combined with a perimeter floor drain and pump. In this way water leaking out of the surfaces is able to find its way between the membrane studs till it reaches a drain at the edge of the floor. It is then led round to a sump pump which pumps it away to an external drain.
Triton Chemical Manufacturing Co. Ltd. have good detailed information on their web site about how this works. It is possible to plaster or render directly onto the membrane or to fix timber studs.
Wet walls and floor for habitable use
This is similar to above but you will need to add a layer of insulation to bring it up to part LThe Building RegulationsThese are the legal regulations which govern how a house is constructed. (not to be confused with Planning Permission which is about whether you are allowed to build the house at all or what it might look like) see Building Regulations), part L is the section which covers energy conservation for new buildings (with part L1A covering new buildings and part L1B covering existing ones) of the Building Regulations. The thickness you add may depend on quite complicated SAPStandard Assessment Procedure - the method used in the building regulations for calculating the energy use of a house. see Part L and SAP calculations. Probably the best type of insulation is closed cell expanded polystyrene because this is not affected in case any moisture might form due to condensation. The insulation should be faced with a dry lining board.
The Building Regulations part A covers the structure of a building. The Approved DocumentsThese are a part of the Building RegulationsThese are the legal regulations which govern how a house is constructed. (not to be confused with Planning Permission which is about whether you are allowed to build the house at all or what it might look like) see Building Regulations) which ensure, if you follow them, that your plans will be automatically approved. The full set of the documents is available here part Apart A of the Building Regulations Approved Documents relates to Structure. See an abridged version which covers house building go into a lot of detail for traditional masonry buildings but almost none for timber frame, steel frame, earth building SIPsStructural Insulated Panels - prefabricated (usually in a factory) timber panels often forming part of an integrated building system and aimed at fast site erection. see more on SIPs etc. For these you will need to consult a structural engineer (while SIPs structures are usually handled by the manufacturer)
With most forms of construction there will be implications concerning fire safety. These are covered in the Building Regulations and you can see examples of how to conform with these in the Approved Documents Part B (Fire Safety)