Roofs, especially flat roofs, are among the most exposed parts of a building. Therefore proper structural composition is a determining factor for the life expectancy of the roof.
In flat roofs with conventional build-up, the thermal insulation is placed above the structural deck but below the water-proofing membrane.
The membrane is thermally isolated from the rest of the roof construction, thus exposed to wide temperature fluctuations with increased risk of premature failure. When applying the "inverted" roof concept, the risk of the failure is minimized. The thermal insulation boards placed on top of the roofing membrane provide protection against a number of damaging factors:
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temperature extremes: with inverted roofs the temperature of the membrane stays within a narrow interval (see the drawing below),
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climatic impacts and UV-radiation,
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mechanical impacts during the construction period, use and maintenance,
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blistering of the membrane: the waterproofing membrane on the warm side of the thermal insulation acts also as a vapour barrier.
The closed cell structure of the ROOFMATE™ SL-A boards is the basis of the excellent physical and thermal properties. ROOFMATE SL-A boards meet the requirements for the insulation materials for inverted roofs:
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no capillarity,
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negligible water absorption,
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resistance to freeze-thaw cycles,
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high mechanical resistance.
The inverted roof insulation system has been proven successful for more than 35 years in Europe. The life-term and long-term behaviour of the system have been examined by independent institutes and building experts several times. Their assessments can be summarized as follows:
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Compared to conventional roofs the life expectancy of the membrane is greater, the risk of failure is reduced, due to the effective and permanent protection for the membrane.
Temperature graph of the waterproofing membrane
a = Conventional flat roof without gravel covering
b = Conventional flat roof with gravel covering
c = Upside-down flat roof insulated with STYROFOAM, protecting the waterproofing membrane
The inverted insulation system is applicable for all types of flat roofs. The standard build-up is the non-accessible roof with gravel ballast on the top. The inverted roof system also works in utilized roof areas such as terraces, roof gardens and parking decks. Since the insulation is placed on the roofing membrane, an energy saving and cost efficient solution for renovation of flat roofs is possible by installing an inverted roof over the existing roof build-up (Plus-roof concept).
The inverted roof concept provides the following advantages:
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protected waterproofing-membrane
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the roofing membrane is installed on the roof-deck (concrete deck),
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simple build-up without additional vapour barrier,
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the installation of the layers above the membrane is independent from weather,
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easy and fast installation.
The standard build-up of inverted roofs contains the following elements:
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waterproofing membrane installed on the sloped concrete deck,
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ROOFMATE SL-A insulation boards with shiplap edge (single layer),
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diffusion-open separation sheet,
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gravel ballast.