PREPARATION OF A SITE AND RESISTANCE TO MOISTURE FROM THE GROUND
(G2.1) The requirements of G2.1 will be met where protection against the ingress of radon gas into dwellings is provided in accordance with the recommendations in ‘Radon: guidance on protection measures for new dwellings in Scotland’.
(G2.2) The requirements of G2.2 will be met where sub-soil drains are provided and laid in accordance with the relevant clauses of BS8301: 1985.
(G2.3, G2.5, G2.6) The requirements of G2.3, G2.5 and G2.6 will be met where the solum and building are constructed as specified below (but note that the diagrams do not show all the structural bracing that might be required).
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Specified constructions |
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The thickness and other dimensions specified are the minimum required unless otherwise stated; greater figures are therefore permissible. |
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Ground supported concrete floors |
Diagram
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A. The solum is brought to a level surface. |
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Hardcore bed 100mm thick of clean broken brick or similar inert material free from fine material and water soluble sulphates in quantities which would damage the concrete; blinded with suitable fine material and consolidated to form a level crack-free surface. |
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Concrete slab 100mm thick with insulation, if any, laid above or below the slab; with or without a screed or floor finish. |
Diagram |
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Damp-proof membrane above or below the slab or as a sandwich; jointed and sealed to the damp-proof course or damp-proof structure in walls, columns and other adjacent elements in accordance with the relevant clauses in Section 3 of CP 102: 1973. |
Diagram
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Suspended timber floors |
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B. The solum is brought to an even surface; any upfilling to be of hard, dry material. |
Diagram |
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Hardcore bed as for A. above; with either a damp-proof membrane in accordance with Section 3 of CP 102: 1973; or concrete 50mm thick laid on 0.25mm (1000 gauge) polyethylene sheet; or concrete 100mm thick; so that in any case the top surface is not below that of the adjacent ground. |
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Suspended timber floor with or without insulation as required. Floor joists carried on wall-plates supported as necessary by sleeper walls with a damp-proof course under the wall-plates. |
Diagram
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Permanent ventilation of the underfloor space direct to the outside air by ventilators in 2 external walls on opposite sides of the building to provide an open area in each wall of either 1500mm2 for at least every metre run of the wall, or 500mm2 for at least every square metre of floor area, this open area also being provided in internal sleeper walls or similar obstructions to maintain the underfloor ventilation; the ventilated space to be 75mm in height from the site covering to the underside of any wall-plates and 150mm to the underside of the floor joists. |
Diagram
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Suspended concrete floors |
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C. The solum is brought to an even surface; any upfilling to be of hard, dry material. |
Diagram |
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Suspended concrete floor of in-situ or precast concrete slabs or beams with concrete or clay infill units; with insulation, if any; with or without a screed or floor finish, or with boards. |
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Permanent ventilation of the underfloor space direct to the outside air by ventilators in 2 external walls on opposite sides of the building to provide an open area in each wall of 1500mm2 for at least every metre run of the wall, or 500mm2 for at least every square metre of floor area, this open area also being provided in internal sleeper walls or similar obstructions to maintain the underfloor ventilation; the ventilated space to be 150mm to the underside of the floor slab or beams. |
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Walls and floors at or near ground level
D. Walls constructed in accordance with clause 10 of CP 102: 1973.
Floors constructed in accordance with clause 11 of CP 102: 1973, except -
ventilation of the sub-floor (clause 11. 8. 4) is to be as in B above.
Structures below ground including basements
E. Structures constructed in accordance with the relevant clauses in Section 2 of CP 102: 1973.
(G3.1) The requirements of G3.1 will be met where the exposed elements are constructed as specified in the relevant provisions below (but note that the diagrams do not show all the structural bracing that may be required).
Specified constructions
The thickness and other dimensions specified are the minimum required unless otherwise stated; greater figures are therefore permissible.
General
In using any of the constructions on the following pages under ‘Wall types’ and ‘Roof types’, the following general provisions apply for walls or roofs as appropriate.
a. Masonry walls of bricks and/or blocks incorporating damp-proof courses, flashings and other materials and components constructed in accordance with the relevant recommendations of BS5628: Part 3: 1985, using a construction to suit the degree of exposure to wind and rain in accordance with clause 21 and as described in BS8104: 1992.
b. Masonry walls incorporating external rendering which conforms to the relevant recommendations of BS5262: 1991, to suit the degree of exposure and the type of masonry.
c. Masonry walls of natural stone or cast stone blocks constructed in accordance with the relevant recommendations of Section 3 of BS5390: 1976 (1984) and to suit the degree of exposure to wind and rain as described in BS8104: 1992.
d. Masonry cavity walls incorporating insulation material, either as a complete or partial cavity fill, where the insulating material is the subject of a current certificate issued under the relevant conditions of an independent testing body, the walls are constructed in accordance with the terms of the certificate and to suit the degree of exposure to wind and rain as described in BS8104: 1992 and the relevant recommendations of the following British Standards.
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Materials or conditions |
British Standards |
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Urea formaldehyde (UF) foam |
BS5617: 1985 and BS5618: 1985 |
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Man-made mineral fibre (slabs) |
BS6676: Part 1: 1986 and Part 2: 1986 |
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Assessment of walls for filling |
BS8208: Part 1: 1985 |
e. Walls or roofs incorporating cladding materials constructed in accordance with the recommendations of the following British Standards or Codes of Practice -
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Materials or conditions |
Element |
British Standards and Codes of Practice |
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Aluminium |
wall or roof |
CP 143: Part 15: 1973 (1986) |
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Galvanised corrugated steel |
wall or roof |
CP 143: Part 10: 1973 |
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Lead |
wall or roof |
BS6915: 1988 |
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Copper |
wall or roof |
CP 143: Part 12: 1970 (1988) |
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Slates and tiles |
wall or roof |
BS5534: Part 1: 1997 |
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Zinc |
wall or roof |
CP 143: Part 5: 1964 |
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Non-loadbearing walls |
wall or steep roof |
BS8200: 1985 |
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Precast concrete cladding |
wall |
BS8297: 1995 |
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Natural stone cladding |
wall |
BS8298: 1994 |
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Flat roofs |
roof |
BS6229: 1982 |
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Bitumen felt |
roof |
BS8217: 1994 |
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Mastic asphalt |
roof |
BS8218: 1998 |
f. Roofs with copper, lead, zinc and other sheet metal roof coverings require provision for expansion and contraction of the sheet material. In ‘warm deck’ roofs, in order to reduce the risk of condensation and corrosion, it may be necessary to provide a ventilated air space on the cold side of the insulation and a high performance vapour control layer between the insulation and the roof structure. It may also be necessary to consult the relevant trade association.