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Under One Roof

Canadian Roofing Reference Manual

13.1.2 Potential Problem Areas

During a visual roof inspection, potential problem areas are those areas that may cause issues currently or sometime in the future.

The following is a list of common problems that could affect the performance of a roofing system.

  • Roof penetrations:
    • BUR felts or membrane flashings which have separated from the base flange of roof jacks/anchors or from the flashings.
    • Problems will also occur when the caulking around pipe penetrations begins to deteriorate.
  • Blisters or buckles will occur in the BUR or modified bitumen membrane systems when moisture is either trapped during installation or enters through penetrations in the membrane. Blisters and buckles will have a spongy feel to them.
  • Fishmouths may occur along the edges of rolls of felt, modified bitumen membrane plies or single ply membrane seams. Fishmouths are typically small funnel shaped openings, which if not repaired, will leave BUR felts exposed to the elements or will result in moisture entry in modified bitumen or single ply membranes. Ridges are long, narrow wrinkles which usually occur along joints in the deck, insulation, or membrane substrate. They are caused by either sub-surface movement or material movement related to moisture within the roof system, perhaps related to an inadequate vapour retarder. Ridges will typically weather more quickly and are more easily damaged than the adjacent roof membrane.
  • Alligator cracks are small cracks on a smooth surfaced BUR membrane roof. Shrinkage of the surface is caused by oxidation of the bitumen coating. Alligator cracks may extend down to the membrane, causing a stress concentration that can damage the membrane reinforcement and allow water to enter the system. Scouring is a term used to describe the removal of a ballast or granular surface by either wind or flowing water. Scouring will leave the underlying membrane components exposed to the elements. If not corrected, the roof membrane will deteriorate more quickly.
  • Gravel stop flashing metal expands and contracts at a greater rate than the membranes that are bonded to it which may cause the felts or membrane strip flashings to split at or near the metal flashing joints. These splits could allow water to enter the roof system.
  • With single ply membranes, look for popped up fasteners, cracks or tears in the membrane and improperly bonded seams. Check the seams visually and, for thermoset membranes, by sliding a seam probe along the seam.
  • Leaks in steep roof materials commonly occur because of improperly installed valleys and roof jacks. Leaves and debris will sometimes collect in valleys and cause water back up.
  • Leaks will occur if shingle tabs are missing.
  • Splits in wooden shingles can cause leaks if the splits line up with the joints in the underlying shingle courses.
  • Along eaves trough, damage may occur to the eaves if the eavestrough nails are installed at an angle which slopes toward the facia. Ensure that the eaves trough and rainwater leaders (downspouts) are unobstructed.
  • Condensation can cause minor ceiling stains. Condensation occurs when moist air comes into contact with a cold surface. In below freezing conditions, condensation will build-up and turn into ice until the outside temperature is warm enough to melt it. For attics beneath steep sloped roofs, this process occurs under the deck and the meltwater can enter directly into the attic insulation and/or the building interior.
  • In the winter months, free flowing attic vents may allow drifting snow to enter the attic. When they melt, serious damage could occur to the roofing system.
  • For steep sloped roof systems including shingles and exposed fasteners metal roof systems, fasteners can back out resulting in moisture entry.

It is recommended that any potential problems should be repaired as soon as they are recognized.

A preventative maintenance schedule should be set-up as part of regular maintenance of a roofing system. This will assist with maintaining the expected performance during the lifespan of the membrane and reduce the possibility of problems occurring at a later date.