Building Soluti Insulating inverted flat roofs with STYROFOAM Solutions: basic principles

STYROFOAM-A Dow Building Solutions’ STYROFOAM™-A products include ROOFMATE™-A materials for roofing applications. STYROFOAM-A products use carbon dioxide as the main blowing agent - the Ozone Depletion Potential (ODP) is zero and the Global Warming Potential (GWP) is less than five. ROOFMATE SL-A and ROOFMATE LG-A ROOFMATE SL-A is the STYROFOAM Solution for insulating inverted roofs. The boards are unaffected by the conditions encountered on flat roofs, including wide fluctuations in temperature and repeated freeze/thaw cycles. ROOFMATE SL-A insulation is intended for use on heavyweight decks...

Insulating inverted roofs Basic principles The performance and longevity of flat roofs depends upon many factors, including the position of the insulation within the construction. If insulation is placed below the structural deck (cold roof construction) the structure remains cold and there is a considerable risk of condensation; for that reason cold deck roofs are seldom used. Insulation placed above the structural deck and beneath the waterproof layer (warm roof construction) reduces the risk of condensation but, because the waterproof layer is thermally isolated from the rest of the roof construction,...

Insulating inverted roofs Construction of the inverted roof Roof loadings In the inverted roof system insulation is laid over the waterproofing layer and suitably loaded to restrain it against flotation and wind uplift and to protect it against damage. The basic roof structure may be of concrete, metal or timber: it must be strong enough to withstand the maximum predicted loads with a suitable factor of safety. Inverted roofs are subject to three main loads: ››› dead loads: the self-weight of all the materials used: for calculation advice see BS 6399: Part 1 ››› wind loads: the positive and negative...

Insulating inverted roofs This ‘rainwater cooling effect’ requires an increase in insulation thickness in order to meet BS EN ISO 6946. However, this increase can be substantially reduced by using the ROOFMATE MinK system, which helps to minimise the heat loss due to rainwater cooling and therefore the amount of insulation required. The inverted roof construction can greatly reduce the risk of condensation in an existing building by keeping the roof structure and the waterproof layer above the dew point temperature. Where the building is likely to have a high level of humidity, as in the case...

Insulating inverted roofs They offer adequate resistance to the external spread of fire as required by Building Regulation B4 (Regulation 19 in Scotland). For further information on the fire performance of ROOFMATE boards see BS 6203. Roof falls and drainage Good drainage is vital to the long-term performance of a flat roof. As with any building element, when designing a flat roof, it is good design practice to follow and adopt relevant design guidance. The most referred to guidance is that of BS 6229:2003 – flat roofs with continuously supported coverings which recommends an appropriate fall...

Insulating inverted roofs Roof waterproofing The inverted roof concept can be used with a wide range of waterproofing materials, including mastic asphalt, high performance built-up bitumen felt, hot melt modified bitumen, PU based systems and single ply polymeric membranes. Seek advice on compatibility with waterproofing materials from suppliers. - to reduce the depth of ballast required to counter board flotation to 50 mm washed 20/40 aggregate, irrespective of the insulation thickness, use a loose-laid non-woven geotextile e.g. ROOFMATE MK lapped 300 mm. Separating layers The recommendations...

Recommendations STYROFOAM products include FLOORMATE, ROOFMATE and PERIMATE. STYROFOAM products contain a flame retardant additive to inhibit accidental ignition from a small fire source. STYROFOAM is, however, combustible and if exposed to an intensive fire may burn rapidly. During shipment, storage, installation and use STYROFOAM products should not be exposed to flames or other ignition sources. Fire classification is based on small scale tests, which may not reflect the reaction of the products in its end use state under actual fire conditions. STYROFOAM products should, when installed, be...