Suspended concrete ground floors - damp proof membrane and ventilation

A suspended concrete ground floor should meet the requirement to resist the passage of moisture from the ground if it incorporates (see Diagram 5.4) – (a) a damp proof membrane; and (b) where there is a ventilated air space below the floor it should measure at least 150 mm clear from the ground to the underside of the floor (or insulation if provided). The ground below the floor should be free of organic material. Two opposing external walls should have ventilation openings placed so that the ventilating air will have a free path between opposite sides and to all parts.