Protection from hot flue gas temperatures not greater than 250°C

Table 5.3 Protecting buildings from hot flue gas temperatures not greater than 250ºC Flue pipe: A flue should be not less than 25 mm from any combustible material, measured from the outer surface of the flue wall, or the outer surface of the inner wall in the case of multi-walled products. Where passing through a combustible wall, floor or roof (other than a compartment wall, floor or roof) a non-combustible sleeve enclosing the flue pipe or chimney should be used which has a 25 mm airspace to the relevant flue wall. The airspace can be wholly or partially filled with non-combustible insulating material. Factory-made chimney designated in accordance with BS EN 1856: 1: Install in accordance with Section 2 paragraph 2.37 of this Technical Booklet Factory-made chimney designated in accordance with BS EN 1856: 1 and BS EN 1856: 2: Install in accordance with Section 2 paragraph 2.37 of this Technical Booklet Masonry chimney: Provide not less than 25 mm of masonry between the flues and any combustible material Flue block chimney: Provide flue block walls with a thickness of not less than 25 mm Flue assemblies for room-sealed appliances: (a) flues passing through combustible walls should be surrounded by insulation material not less than 50 mm thick. (b) provide a clearance of not less than 50 mm from the edge of the flue outlet to any combustible wall cladding