Sheet membrane roofing
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Sheet membrane roofing – dirt on membrane roof
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Accumulation of dirt/debris not flushed off by rain
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Overhanging branches
Sheet membrane roofing – deterioration along substrate joints
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Movement in the plywood substrate
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Omission of bond breaker tape at joints
Sheet membrane roofing – impact or puncture damage
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Careless walking on roof
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Membrane that is not suitable for foot traffic (for example, mineral chip surface on polymer modified bitumen)
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Sharp or hard objects on the roof
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Nails in substructure have popped, puncturing membrane from underneath
Sheet membrane roofing – surface deterioration (cracking, crazing)
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UV light degradation
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Expansion/contraction of substrate resulting in over-stressing and failure of the membrane
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Membrane (for example, a mineral chip surface on a polymer modified bitumen) is not suitable for foot traffic
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The material is at the end of its serviceable life
Sheet membrane roofing springy or spongy to walk on
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Damage to the substrate and/or framing due to water entry through the membrane or through adjacent wall claddings
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The substrate material is not thick enough to span rafters/joists
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Particleboard has been used as a substrate and has deteriorated
Water ponding on sheet membrane roofing
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Drainage is poor due to insufficient fall to outlets
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The drainage outlet is blocked
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The outlet is too small for the volume of water on roof
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The roof slope is not towards the drainage outlet
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The substrate has slumped, resulting in localized ponding
Nails have popped in substrate under sheet membrane roofing
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Substrate movement such as expansion/contraction
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Substrate deterioration
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Substrate was nail-fixed rather than screw-fixed
Bubbles in sheet membrane roofing
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Poor adhesion of the membrane to the substrate
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Adhesive misses – the membrane is not fully adhered to the substrate
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Moisture from a damp substrate or roof framing is being drawn to and trapped by the membrane
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The framing and/or substrate moisture content was too high when the membrane was installed
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Moisture in living spaces below is getting into the roof space (typically via open downlights) and being drawn through the substrate where it is trapped by and accumulates under the membrane
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Subsequent coats of liquid-applied membrane are applied before preceding coats have cured
Deterioration of sheet membrane roofing patching
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Incompatible patching material was used; for example, rubber membrane used to patch bitumen-impregnated membrane
Delamination of sheet membrane roofing from substrate
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Incompatible membrane material was laid over substrate, such as rubber membrane over bitumen-impregnated membrane. The adhesives used in a rubber-based membrane are solvent-based and react with the oils in the asphalt, causing the membrane to separate from the asphalt
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Poor installation
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Subsequent coats of liquid-applied membrane were applied before preceding coats have cured
Sheet membrane roofing – lifting of sheet joints
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Loss of adhesion at the joint
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Substrate movement has caused damage to the membrane
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Water has got under the membrane causing a breakdown of the adhesive
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The joint is within an area where water ponds
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Adhesive failure at joints
