General guidance on moisture resistance in floors

This section gives guidance on the resistance to the passage of moisture from the ground in relation to the following floor types – (a) ground supported floors (see paragraphs 5.3 to 5.11); (b) suspended timber ground floors (see paragraphs 5.12 and 5.13); and (c) suspended concrete ground floors (see paragraphs 5.14 to 5.19). Floors next to the ground should – (a) resist the passage of moisture from the ground to the upper surface of the floor; (b) not be damaged by moisture from the ground; (c) not be damaged by ground water; (d) resist the passage of gases from the ground; and (e) in dwellings, be designed and constructed so that their structural and thermal performance are not adversely affected by interstitial condensation (see Section 8). To comply with Regulation 26 floors in some localities may need to resist the passage of hazardous gases from the ground such as radon or methane. Protective measures which include a gas resistant barrier can, with proper detailing, function also as a damp proof membrane (DPM). For specific guidance on radon protection refer to paragraphs 3.10 to 3.12.