Inspecting your roof from outside

What to look for

• Blistered, curled or split shingles.
• Loose or missing shingles or tiles.
• Broken or loose shingles at the ridge lines and hip lines.
• Loose nails. A loose nail means an open hole, which can cause leaks and water damage.
• Exposed nails. These also lead to leaks, as water seeps around the head of the nail.
• Dark patches on asphalt shingles, or large amounts of granules in the gutters. This can mean the granular coating is wearing away and needs replacing.
• On a slate roof, dark patches could indicate mould — but they are often just discoloured places where trees drip repeatedly on the slates. Check inside for dark or discoloured drywall before calling anyone.
• Sagging, either along the ridges or in the centre of the roof.
• Rusty or corroded flashing and loose shingles in the valleys, at plumbing vents, or near chimneys. Leaf debris in those places causes problems if it is not cleared at the end of the season.
• Rusty metal or loose shingles where a vertical side of the house meets the roof.
• Overflowing gutters, or water pooling near the foundation.
• On a flat roof, blisters in the coating, or depressions near the vent pipe. Watch for separations in the flashing and clogged drains too.