Exposed soffit floors

It is possible to achieve very high levels of thermal insulation in exposed upper floors. The designer has a choice of where to position the insulation: for concrete floors, either above or below the floor, or for timber joist floors, between the joists.

If insulating below the structural floor, the insulation can be laminated to a variety of materials thus the floor can be insulated and finished in one process.

Insulating above the structural floor reduces the thermal mass of the floor allowing for fast warm up. However, if only part of the floor on that storey is exposed it may cause problems with steps between finished floor levels.

When insulating between timber joists, the whole depth of the joist can be utilised as an insulation zone. If mineral wool insulation is installed between the joists, a very high insulation value can be achieved without increasing the depth of the floor construction or adding significant weight to the structure.

The fire resistance of the exposed floor should comply with Building Regulation requirements. This will be between 30 and 120 minutes, depending on the purpose group of the building and its height above ground.

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