C9: Cladding9.1 VERTICAL TG AND V TYPE
External cladding shall be tongued, grooved and v-jointed vertical Douglas fir pressure impregnated to a minimum of Hazard Class 3A in accordance with EN 335, EN 350 and EN 351. Following preservative treatment the timber shall be re-dried to a moisture content of 16±3%. Cladding boards shall be 100x25mm (see B12.2.4) finished dimensions, with a stress-relieving back groove, all as shown in the detail cladding board profile drawing. Boards shall be fixed through the v-joint with silicon bronze or stainless steel ringshank nails, to 50x36mm horizontal battens and vertical counter battens at a maximum of 450mm centres treated to hazard class 2 (minimum). All end grain to be sealed with aluminium primer.
Provide a 25mm minimum continuous clear cavity behind the cladding boards. Stainless steel insect mesh shall be fitted to all ventilation openings to the wall cladding.
9.3 BREATHER MEMBRANE
The breather membrane shall comply with BS 4016 or shall be of a brand name specified by the architect. The breather membrane shall be fixed with stainless steel staples at 300mm centres (or as specified by the manufacturer) with minimum overlaps of 150mm at junctions. The breather membrane shall also be turned-in at window openings so as to properly lap with the internal vapour control layer, and run below DPC at ground level. See Section B for details of breather membrane/DPC interfaces.
No wood fillers shall be used externally. Internally no wood fillers may be used where a translucent wood finish is used. Fillers may only be used in other situations with the architect's permission.