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Under One Roof

Canadian Roofing Reference Manual

13.2.6 Steep Roofs

When repairing steep roofs, it is recommended that all materials be obtained from the original manufacturer. This may enable you to match the colour of the material to that of the existing roof.

Valley leaks are generally caused by one of the following:

  • Nails which have been placed too close to the centerline.
  • Untrimmed butts.
  • Insufficient metal width.
  • Improper weaving.

A roof, with any one of the above problems should be repaired and brought up to standards immediately. The same is true for improperly installed roof jacks and flashings.


Remove shingles by pulling the nails from the two courses directly above and from the shingle to be removed. This will allow you to slide the damaged shingle down the slope. Slip the new shingle under and reinstall the nails.

  • Asphalt shingles, which are starting to curl or show signs of granular loss, should be replaced. Curls act as a dam and cause water to run horizontally.
  • Wooden shingles, which are starting to split, should be replaced. A split shingle is a sign that the roof is beginning to dry out. If the split is isolated, sheet metal may be slipped under the damaged shake or shingle. This will eliminate the leak.
  • Condensation often occurs in areas around exhaust fans. Condensation potential can be minimized by insulating the exhaust duct through the attic and by installing a cap on the top of the pipe which contains a damper. The damper helps prevent cold air from entering the exhaust duct.

Insufficient attic ventilation will also cause condensation. This may be addressed by installing additional vents on the roof, soffit, or on both. It may also be appropriate to access and seal the ceiling air/vapour retarder at penetrations (electrical boxes, cable penetrations at the top of stud walls, exhaust fan penetrations, etc.) to reduce the flow of warm moist air into the attic space.

If condensation occurs on a cathedral ceiling, it may be an indication that the rafters have not been strapped to provide cross ventilation in addition to the items above. To correct this problem, install a continuous vent across both the ridge and eave. This will ensure that the air space between each rafter is ventilated.