Tips on tar-and-gravel roof repairs

October 16, 2014

For tar-and-gravel roofs to do their job in Canada’s harsh weather, regular inspections and repairs may be required, especially when water pools.
To be tarred and feathered isn’t much fun. But having a tar-and-gravel roof is a good thing.

It’s one of the most common systems for flat or nearly flat roofs, where layers of asphalt-saturated felt roof paper (tar-paper) are mopped with hot asphalt. Pea-sized gravel is distributed on top, with some pieces embedding in the asphalt and some staying loose, providing a measure of protection against puncture and the effects of sunlight.

But Canada’s rain and winter cold can take a toll on tar-and-gravel roofs, so extra vigilance is required to keep them in good repair and watertight. They need to be tightly sealed, with a gentle slope to carry liquid to the drains.
Start your inspection
To look for damage or problem areas, you should get on the roof with work gloves, kneepads (the gravel can hurt as you kneel for inspection), and stiff push broom, so you can push aside loose gravel when necessary to inspect what’s going on underneath.
What to look for
Here are danger signs to look out for:

  • Blistering — resulting from air or water becoming trapped between layers of the roof.
  • Water pooling — if water lies on the roof for more than 48 hours, its weight can damage the roof and cause depressions that can affect drainage.
  • Growth — if vegetation is growing on the roof, it’s a sign you’ve had water-pooling problems. The plant roots and the held moisture can also damage the roof.
  • Piles of gravel near drains and low spots — sweep these aside to see if the roof is exposed or cracked.
  • Metal flashing where pipes come through the roof — check if the tar overlapping the flashing is cracked or missing.
  • Roof-edge flashing — also look for areas where the overlapping tar is cracked or missing.

How to fix a leak

  • Find the leak, often in low spots where water has been pooling on the roof.
  • Clear away the gravel from around this area and make sure the roof is dry.
  • Cut off any blisters and pull apart any cracks to let the areas underneath dry.
  • Apply tar to the cut areas, folding the cut edges into the tar.
  • Cut tar-paper to cover the area, laying it over, ensuring that it is submerged in the tar.
  • Trowel more tar over the fabric and smooth it out beyond the edge of the repair.
  • Move stones back by hand across the repaired area, to protect it from the weather.

Then go back inside and pat yourself on the back for a job well done.

Tips on tar-and-gravel roof repairs
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