Site preparation & 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 CUBE6 provides a free vent area of 6600mm² and should be fixed at no more than 3 metre centres. 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.

A suspended concrete floor should incorporate

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
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).
Where the ventilation referred to above 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

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