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Cold-applied liquid coatings Advantages
Disadvantages
Applications
• Easily applied • Suitable for a variety of substrates • Chemical resistant • Excellent tensile strength • UV resistant • Energy efficient (white only) • Great for waterproofing complex roofs • Monolithic membrane without joints/laps
• Cannot be installed if weather is too hot or cold • Cannot be applied over silicone-based coatings • Will fail dramatically if substrate preparation is incorrect • Many systems do not have multi-layered redundancy
• Commercial and residential • Refurbishment • Replacement • New build
Green roofs There are two variations of green roofs, extensive and intensive Extensive green roofs Advantages
Disadvantages
Applications
• Requires minimal maintenance • Hardy species of plant life • No irrigation required • Modest structural load • Wind resistant • Used on sloped/pitched roofs • Improves air quality • Reduce run-off • Desirable aesthetics
• Only supports drought-tolerant plants
• Commercial and residential • Refurbishment • Replacement • New build
Intensive green roofs Advantages
Disadvantages
Applications
• Boosts biodiversity • Creates additional usable space • Improves air quality • Reduce run-off • Desirable aesthetics
• Labour intensive • Requires regular maintenance • Requires irrigation • Very heavy structural load • Deep construction
• Commercial and residential • Replacement • New build
l Reinforcement tensile strength: The stronger the reinforcement within the membrane, the better it is able to cope with the expansion forces and other stresses. Generally, the higher the number the better, but dimensional stability and elongation also have to be taken into account. Metal l Roof pitch: Some standing seam systems are capable at pitches of 1.5 degrees. Most will require at least 4-6 degrees of slope, otherwise, leaks will become apparent at laps and joints in the metal panels. l Wind uplift and loading: Especially important with metal systems that are self-supporting and fixed to a
subframe or steel purlins. The profile, gauge and material will determine the strength of the metal panel, and should be considered along with the span the panel is expected to bridge and its subjected loading. l Fire resistance: Metal roofs are generally resistant to the spread of and penetration from fire. Steel or aluminium roof sheet with less than 200g per sq m of organic coating automatically complies to Building Regulations, with a Broof T4 classification without testing under European Standard EN 13501-5, Fire classification of construction products and building elements – Classification using data from external fire exposure to roof tests.
The best way to ensure your roof is well designed is to get expert advice. Your roofing manufacturer will have a wealth of experience l Incompatible materials: Different metals tend to react poorly with each other. For example, copper and zinc placed together cause bimetallic corrosion. Cold-applied liquid coatings These should be treated in a similar vein to other systems. Roof slope, drainage and fire considerations should be kept in mind. Also: l Incompatible materials: Must again be avoided. For example, polyurethane or acrylic coatings must not be used over methyl methacrylate (MMA) covering in a refurbishment project and siliconebased materials are generally incompatible with all other coatings. l UV stability: There are products designed for internal use that if used externally would break down as a result of UV radiation. l Odour: Some coatings can be pungent during application which can be problematic on sensitive sites such as hospitals or schools, where low-odour coatings should be specified. Green roofs l Roof pitch: While intensive green roofs can be installed on a flat roof deck with suitable drainage, for extensive green roofs generally a minimum fall of 1:60 is desirable. The growing medium and drainage system must be designed to keep the vegetation above any standing water.
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