How to repair a flat garage roof

Updated July 20, 2017

Some flat garage roofs feature multiple layers of felt and asphalt while others are simply metal. The type of repair your garage roof needs depends on the type of roof the garage sports. Rainwater and snow can puddle on flat roofs and cause damage. Flat metal roofs often have problems with stagnant water, which can cause corrosion and result in leaks. Layered roofs can start to delaminate over time and require repairs or even replacement. Repairing small damages in both metal and layered roofs is a moderately simple project that will prolong the life of your garage roof.

Metal roof repair

Clean the damaged area with a wire brush.

Spread a layer of roofing cement around the damaged area with a putty knife.

Cut a piece of roofing mesh to overlay the damaged area, using tin snips. Set the mesh into the roofing cement covering the damaged area.

Spread layers of roofing cement atop the roofing mesh, working the cement through the mesh with a putty knife to bind it to the roof. Cover the mesh completely and let it dry.

Layered roof repair

Scrape away any surface gravel from the damaged area with a spade.

Cut a rectangle around the damaged area using a utility knife, and remove it.

Spread a thick layer of roofing cement into the removed area with a putty knife.

Patch the area by setting a replacement piece of roofing material over the roofing cement and pressing it down until secure.

Spread a thick layer of roofing cement over the roofing material patch with a mason's trowel. Cover the patch with surface gravel.


Use caution when working on flat roofs and using ladders. If the metal roof is too badly damaged, it is advisable to have it replaced. Consult a professional if a layered roof is bubbling up or making a sucking sound when walked upon.

Things You'll Need

  • Wire brush
  • Roofing cement
  • Putty knife
  • Roofing mesh
  • Tin snips
  • Spade
  • Utility knife
  • Replacement roofing material
  • Surface gravel
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About the Author

Rachelle Proulx has been writing since 2000. She co-owns a pet-sitting company, providing her the experience to cover pet care and small business. Proulx is also a flooring specialist who writes about flooring options, preparation, application and maintenance.