Floors: Beam and Block floors with aircrete
The construction of a beam and block floor is similar to that of a suspended timber floor, but uses small pre-cast, pre-stressed inverted concrete T-beams with aircrete blocks laid between the beams.
It is suitable for the construction of both ground floor and intermediate floors of homes and commercial buildings, but without the shrinkage, flexing, bouncing or squeaking associated with timber floors. The system can also be used for the construction of floors of domestic garages
Beam and aircrete block floors are a quick, easy and economical solution to installing suspended floors. Depending on the pre-stressed concrete beams used, beam and block floors can generally span further than timber joists, typically 6m, potentially reducing foundation costs.
Because the floors are suspended, minimal groundwork is required when used to construct ground floors. Further, the installation of a beam and block floor is not usually weather dependent and can reduce site delays that other floor construction methods may encounter. The speed of construction means the floor can be used to provide a working platform for early access of follow-on trades.
The aircrete advantage
Compared to timber floors, beam and aircrete block floors have numerous benefits including:
- Durability, strength and stability
- Improved thermal performance
- Thermal mass
- Improved acoustic performance from the inherent mass of concrete and Fire resistance
- Unaffected by damp, rot and vermin
- With the addition of an appropriate screed, beam and block floors can also easily accommodate underfloor heating systems
H+H products for beam and block floors
The precast concrete beams are laid in rows supported by the perimeter walls and on internal load bearing walls. Celcon Block Standard Grade 440 x 215 x 100mm is ideal as an infill between the precast concrete beams.
Beams are typically spaced 440mm apart for a standard floor, or they can be placed 215mm apart to allow the blocks to be placed sideways to accommodate higher loads and/or longer spans
Typically a 4:1 sharp sand/cement grout mix is brushed into the joints to provide a rigid construction.
For ground floors, insulation is usually positioned on top of the beam and aircrete block floor and covered by a sand cement screed, the choice of insulation material will determine the insulation thickness required to meet Part L of the Building Regulations. Depending on the floor covering used, a vapour control layer may be required to keep the moist room air on the warm side of the insulation.
The ventilated void beneath the ground floor should be at least 150mm. In some areas of the country where radon gas occurs, a gas membrane will also be required to stop the gas entering the building and the ground floor will need to be ventilated. In the England and Wales the Building Regulations Approved Document C provides guidance on some of the requirements of suspended ground floors.
For upper floors, in addition to their robustness the solidity of beam and block offers several advantages over timber floors including: excellent acoustic separation between floors, better fire, and concrete's thermal mass can help reduce summer overheating.