Every tool shed and maintenance truck needs a few go-to staples—duct tape, WD-40, and a sturdy pair of gloves. But if you’re working on or around a roof, there’s another must-have you should never overlook: plastic roof cement.

Whether you’re patching up a leaky seam or sealing flashing in bad weather, this thick, asphalt-based compound is your best friend when a roofing problem can’t wait.

What Is Plastic Roof Cement?

Plastic roof cement is a blend of asphalt, mineral fillers, and fibers. It’s designed to seal and patch areas on roofs, chimneys, vents, and flashings. It adheres to wet or dry surfaces and can be used in both emergency patches and long-term repairs.

You’ve probably seen it before: thick, black, and sticky. It comes in cans or caulk tubes and is usually applied with a trowel or putty knife.

Common Uses for Plastic Roof Cement

1. Emergency Leak Repairs
 Got a drip during a downpour? Plastic roof cement can be applied in wet conditions, giving you an immediate (though temporary) fix until permanent repairs are made.

2. Sealing Flashing and Joints
 Anywhere metal flashing meets shingles, brick, or wood, there’s a chance for water to sneak in. Plastic cement fills those gaps and keeps the elements out.

3. Patching Cracks and Holes
 Over time, roofs develop cracks, pinholes, or gaps in seams. This cement fills those voids and forms a watertight seal.

4. Chimney and Skylight Repair
 Where the roof meets brick or skylight frames, there’s often movement and potential for leaks. Roof cement holds its seal even under temperature swings and minor movement.

5. Reinforcing Roof Edges and Vents
 Use it to strengthen weak areas or cover vent edges where wind-driven rain might sneak in.

Application Tips

  • Clean First: Remove dirt, loose materials, and moisture when possible.
  • Use Generously: Don’t be stingy—it’s meant to be applied thick.
  • Feather the Edges: Smoothing the edges out helps prevent water from getting underneath.
  • Let It Cure: While it sets quickly, full curing can take up to 24 hours depending on thickness and conditions.

When Not to Use It

Plastic roof cement is a patch—not a replacement for proper flashing or new shingles. It’s ideal for quick fixes and preventative maintenance but shouldn’t be used as a permanent roofing system.

It’s also not meant for rubber (EPDM) roofs unless the label specifically says it’s compatible.

Some Brands We Carry at CEM

At CEM Industrial Supply, we stock top-performing plastic roof cements from trusted names like:

  • Tamko
  • Henry
  • Black Jack
  • Gardner
  • Karnak

Our team can help you choose the right one for your job—whether you’re patching up a metal barn roof or sealing chimney flashing on a commercial property.

Final Thoughts

Plastic roof cement isn’t glamorous—but it gets the job done. Fast. It belongs in every contractor’s and facility manager’s toolkit for those jobs where time, weather, or access makes a full repair impossible.Need a can today? Stop by CEM Industrial Supply, or give us a call and we’ll have it ready for pickup.