Roofing cement: what it is, what it fixes, and how to use it
Roofing cement is a thick asphalt compound, troweled or caulked on cold, for patching splits, cracks and seams and sealing around chimneys, vent pipes and flashing. Asbestos-free asphalt roof cement is made to ASTM D4586; some, such as APOC 109, go on wet or dry and hold on vertical surfaces without sagging.
Anthony Hicks30+ years in construction. Updated November 5, 2026.
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What it is
Roofing cement, also sold as roof cement or plastic roof cement, is a thick asphalt compound, soft enough to trowel and stiff enough to stay where it’s put. It’s applied cold, from a can with a trowel or from a caulk tube, and cures in place.
Asbestos-free asphalt roof cement is made to ASTM D4586. APOC 109, for one, meets ASTM D4586 Type I and ASTM D3409, and the residential code’s table for modified bitumen roofs lists asphalt cement among its materials (IRC Table R905.11.2).
What it fixes
APOC lists these uses for its asphalt roof cement:
- Splits, cracks and seams in gravel, cap sheet and smooth asphalt roofs, and in shingle roofs.
- Sealing around chimneys, vent pipes, gravel guards and downspouts.
- Cracks in concrete.
- Below grade, as a mastic in foundation waterproofing and dampproofing.
How to apply it
- Clean the spot: loose granules, dirt and old crumbling patch off.
- Work the cement in with a trowel or putty knife, past the edges of the crack or seam.
- Reinforce bigger cracks with a strip of reinforcing fabric pressed into a first coat, then cover it with a second.
- Seal the edges of flashing and around pipes with a bead, feathered out onto the roof.
Read the label for the temperatures and surfaces a cement allows. Some are made to go on wet: APOC 109 can be applied to a wet or dry surface and bonds underwater.
When a patch isn’t enough
Roofing cement seals small leaks and seams. Missing shingles, loose or rusted flashing, a cracked pipe boot or a worn-out slope need the part replaced. The roof repair cost guide prices small repairs and sections, and the guide to the parts of a roof shows the flashing and the rest.
Common questions
Is roofing cement the same as tar?
Both are asphalt-based. Roofing cement is applied cold from a can or tube; “tar” usually means hot asphalt mopped onto built-up and modified bitumen roofs.
Can you apply roof cement in the rain?
Some, yes. APOC 109 is made to go on wet or dry surfaces and bonds underwater; the label on each product says.
What sizes does it come in?
Caulk tubes for small jobs and gallon cans for bigger ones; APOC 109 comes in a 10.1 oz tube and 1, 3 and 5 gallon cans.
Does roofing cement work on shingles?
Yes, for patching splits and cracks and sealing around flashing on shingle roofs, as APOC lists. A shingle that’s missing or torn is replaced.