Floors must be designed as a whole element taking account of all the functional requirements. The position of the insulation is influenced by the type of construction, the predicted floor loading and the heating regime.
Buildings which are to be intermittently heated are usually designed with 'fast thermal response' fabric (low thermal mass) with the thermal insulation on the inside of the structure. Heating systems which utilise the structure as a heat store (high thermal mass) require the thermal insulation to encompass as much of the structure as possible.
The design of foundations and groundbearing floors is influenced by the site on which the building is to be constructed. The load bearing capacity of the soil should be established before design work is undertaken.
Whilst a groundbearing floor is usually an effective construction for domestic and commercial buildings, a ground floor should be suspended in the following circumstances:
- domestic buildings on sloping sites where more than 600mm depth of infill would be required
- where the bearing capacity and nature of the ground varies from one part to another
- where the ground is of shrinkable clay, expansive material or other unstable soil type.
The site should be assessed for hazards likely to affect substructure and groundbearing floors such as chemicals (particularly sulphates), contaminated material above or in the ground and waterlogged ground.
In some parts of the UK special precautions are necessary to reduce the entry of radon gas. Details of those geographical areas may be obtained from the Department for Environment, Food and Rural Affairs (DEFRA) at www.defra.gov.uk. Floors must also be resistant to ground hazards as outlined in building regulations.