Tar & Gravel Roof Repair Around a Skylight

About Tar and Gravel Roofs

• Tar and gravel surface coverings are part of a built-up roof system, called BUR in the building industry. BUR systems consist of overlapping layers of sheeting, usually asphalt or rubber. BUR installation methods include hot-mop, nailing and torch down. The tar and gravel component forms the top layer of a BUR system. Your skylight's proximity to the tar and gravel layer of the roof depends on the design of the skylight's mounting hardware. Some skylights sit above the tar and gravel and others are nested within the tar and gravel.

Skylights on Tar and Gravel Roofs

• On flat roof systems, such as tar and gravel, skylights typically sit on top of a wooden frame called a curb. Skylight curbs protrude above the roof's surface, encouraging water to shed away from the skylight's frame and opening. Roofers usually lap sheets of roofing material over the curb before installing the skylight. Some skylights have frames that extend halfway or less down the side of the curb; in this case, roof coverings climb up the curb and meet the perimeter of the skylight's frame. Alternatively, a skylight frame entirely covers the curb, bends at a 90-degree angle and extends onto the flat roof surface. In this case, tar and gravel actually cover a portion of your skylight. If your skylight has a flange that rests on the flat roof surface, you should take care not to damage it while scraping damaged tar and gravel from the roof.

Temporary Patches

• Manufacturers offer trowel-applied roof cements for temporary patches or emergency repairs on flat roofs. If you're working in rainy weather, look for a patching compound that cures under wet conditions. Roof patching compounds are thick, sticky compounds, so it's easy to squeeze them into cracks and holes with a trowel. For skylight repair, you can temporarily stop leaks by applying roof patch material around the base of the skylight, up the curb and at the joint between the skylight frame and curb. For the best results, you should remove loose tar and gravel from the repair area before applying the patch. When the weather improves, return to skylight to perform a permanent repair.

Removal and Replacement

• Permanently repairing around a skylight requires removing damaged tar, gravel and built-up roof paper until you reach an area that remains intact. This demolition is necessary to ensure that you don't encase damaged materials beneath the repair. To remove tar and gravel roofing materials, use heavy-duty roof scrapers or roofing shovels. You don't need to replace the removed materials with tar and gravel; repair fabric and asphalt paper are suitable substitutes. The replacement materials should lap over the skylight's flange and climb up the curb. For small repairs, you can use trowel-applied roofing cement. For large repairs, use brush or roller-applied roof adhesives.