Insulating ballasted inverted flat roofs with STYROFOAM Solutions
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Dow Building Solutions Insulating ballasted inverted flat roofs with STYROFOAM Solutions

Design considerations Introduction The inverted roof system is ideally suited to flat roofs of heavyweight construction, and offers a durable, attractive roof finish for roofs where maintenance traffic is expected (Figure 1). For the full physical properties and performance characteristics of ROOFMATE SL-A products see separate guide: STYROFOAM performance, product overview and references. The ROOFMATE MinK system STYROFOAM-A and ROOFMATE SL-A STYROFOAM™-A products use carbon dioxide as the main blowing agent - the Ozone Depletion Potential (ODP) is zero and the Global Warming Potential...

Design considerations ROOFMATE MK should be loose-laid over the insulation, at right angles to the slope with 300mm laps running down the slope. This will allow the ballast, 20/40 aggregate, to counter board flotation to be reduced to 50 mm. At upstands and penetrations ROOFMATE MK should be turned up to finish above the surface of the ballast. ROOFMATE MK is a spun bonded polyethylene geotextile with the following properties: ››› water vapour permeable ››› water resistant ››› tear resistant ››› UV stable - can be left exposed outdoors for up to four months ››› fire - melts and shrinks away...

Design considerations Roof falls and drainage Outlet gratings may be raised on spacer rings to reduce the risk of blockage: cut a hole in the ROOFMATE SL-A boards to accommodate the outlets (Figure 2). A paving slab on spacer pads may be used above a flat grating (Figure 4). 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...

Design considerations ➀ paving slabs on spacer pads ➀ ➁ ROOFMATE SL-A ➂ separating layer (if required) ➃ waterproof layer ➄ screed to falls ➅ roof outlet ➆ concrete slab Figure 4 Ballasted inverted roof - outlet protected by paving slabs ➀ paving slabs on spacer pads ➁ ballast ➂ ROOFMATE MK or a suitable separating layer ➃ ROOFMATE SL-A ➄ separating layer (if required) ➅ waterproof layer ➆ concrete slab Figure 5 Ballasted inverted roof - insulation over internal gutter ➀ paving slab on spacer pads ➁ ROOFMATE MK or a suitable separating layer ➃ separating layer (if required) ➄ waterproof...

Installation methods Installation sequence 1. Inspect the roof to ensure it is clean. Plan the installation sequence and the layout of ROOFMATE SL-A boards. 2. Lay the separating layer (if required) over the waterproof layer; lap all edges by 200-300mm, at perimeters and penetrations turn up above the installed thickness of the insulation. Figure 7 3. Lay ROOFMATE SL-A insulation boards in brick bond pattern with shiplap edges pushed together firmly (Figure 7). 4. Insulate upstands with ROOFMATE LG-A boards (Figure 3). 5. Fit ROOFMATE SL-A boards neatly around penetrations (Figure 8). Cut...

Installation methods minimise cutting and wastage ››› take care not to over-stress any area of the roof while distributing the ballast ››› use scaffold boards when barrowing materials over ROOFMATE SL-A boards. Thicknesses: 1 00, 120, 140, 160, 180, 200* mm Board size: 1250 x 600 mm, *2500 x 600 mm Edge profile: butt edge Design loading: 130kN/m2 Fire Classification: Reaction to fire: BS EN 13164 Euroclass E Working temperature range: -50°C to +75°C. ››› careful setting out before installation begins will Specification J21 Mastic asphalt roofing 120/125 J41 Reinforced bitumen membrane roof...

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,...