Design Considerations
Litecast joist and block flooring is the ideal solution for suspended ground floors in housing and non-domestic dwellings.
It has been a requirement of NHBC since 1974 that ground floors must not be supported from dell fill. The ground floor must be suspended where the fill is in excess of 600mm. Failures often occur due to lack of compaction when the fill is less than 600mm, which emphasises the importance of using suspended floors. It is easy to eliminate these problems by using Litecast joist and block floors at ground level.
Where a heavy point load is to be applied to Litecast joist and block flooring i.e. garages, it is recommended that the floor should have concrete of min. grade C20 reinforced with an A98 mesh to distribute the load.
Fire Resistance
There are no fire resistance requirements where Litecast joist and block floors are adjacent to the ground floor.
However, a fire rating of upto 1 hour can be accomodated with the Litecast flowing system at upper floor levels.
Ventilation
Good building practice dictates that any suspended ground floor requires ventilation. The NHBC recommends that the rate of ventilation is not less than 600mm² per metre of external wall. The combined air brick and ventilator supplied by Litecast provides a free vent area of 6600mm². These should be fixed at no more than 3 metre centre as detailed on the Litecast layout drawings. Opposing external walls should have ventilation points to provide a free air path.
If another type of air brick (especially one made from clay) is to be used it may be necessary to increase the number of ventilation points.
Approved Document C 1992
(Site preparation and resistance to moisture)
A suspended concrete floor should incorporate:
a: A damp-proof membrane (to be provided if the ground below the floor has been excavated below the lowest level of the surrounding ground and will not be effectively drained) and
b:In those situations where there is a risk of an accumulation of gas which might lead to explosion, a ventilated air space. This should measure at least 150mm clear from the ground to the underside of the floor (or insulation if provided).
c: Where the ventilation referred to in (b) is provided, two opposing external walls should have ventilation openings placed so that the flow of air will have a free path between opposite sides and all parts. The openings should be large enough to give an actual opening of at least equivalent to 1500mm² for each metre run of wall or 500mm² per square metre of floor whichever is the greater.
No oversite or other seal is required. The only requirement is the removal of top soil and vegetable matter and the provision of a void to accommodate any likely ground movement.
Other items for floor construction
For use in projects that involve etc.
For use in projects that involve etc.
For use in projects that involve etc.