A basement can be a key design solution for optimising development potential.
Higher density development - minimal extra height
The use of a basement provides increased floor area in a development without significantly increasing the apparent size of the building; thereby improving the viability of a development, particularly in areas where building height or size of footprint is restricted. The potential to increase the number of proposed dwellings in one property is boosted if both a basement and habitable roof space are proposed; thereby potentially creating two additional storeys in a similar building envelope.
Maximise site layout - build up to street boundary
By lifting the ground floor level above street level to create upper and lower ground floors, properties can be constructed close to site boundaries while maintaining privcy for occupants. Considerations of Building Regulation Part M requirements for access are required.
Utilise existing slope
Partial basements on sloping sites become viable compared to alternative substructure construction options to make up ground levels.
Protect amenity space
The use of a fully below-ground basement or partially below-ground basement gives increased usable space within the building footprint. Larger dwellings can therefore be built on small sites without losing amenity space around the buildings.
Better use of poor sites with poor soil
Where poor ground conditions necessitate deep foundations, the additional cost can be mitigated by including a basement to add space and therefore value to the proposed new properties.
Where large areas of contaminated soil are removed from site, the viability of including a basement level is increased. If constructed before original ground levels are reinstated, the amount of replacement ground material is reduced and further excavation is unlikely. Back fill will need to be compacted around the walls, but in general the programme of construction is likely to benefit from improved access conditions.
Stable building stock
Basements create a good stable structural base, capable of supporting heavy loads above. By combining foundation design with the provision of habitable space, the extra depth of structure provides the building with greater ability to cope with climate change effects in the soil, such as shrinkage or tree roots. This means buildings with basements are less prone to movement and cracking as a result of potential future changes in soil conditions.
Increased number of plots per hectare
By incorporating facilities such as garages, utility rooms or habitable space at basement level, it is possible to reduce the footprint of a proposed property; thereby increasing the number of houses on a given site or along a fixed street frontage.
Housing using a basement garage requires less street frontage, compared to houses with garages located alongside at ground level.