You can repair a hot tar built-up flat roof with fiber-mesh patching or an aluminum fiber coating.
A flat roof is usually slightly sloped. It may be covered with a granular roll roofing, EPDM (which is smooth surfaced), or modified bitumen (which may be smooth or mineral surfaced). Some flat roofs have hot tar built-up roofing, which may have a gravel surface. If you live in an arid region or an older urban area, you may have a large flat roof. Suburban homes sometimes have small flat sections.
Where the roofing curves to meet a wall or chimney, the material may loosen along its topmost edges. Apply plenty of roofing cement to fill the void and smooth the cement so water can run off unimpeded.
An application of aluminum fiber coating quickly seals many small leaks and can prolong the life of a roof. It cannot be applied over a gravel-topped or mineral surfaced roof however.
1 to 2 hours for most repairs
Utility knife, trowel, squeegee/broom for applying aluminum coating, hammer
No special skills required
Inspect the roof for bubbles, cracks, and voids.
Roofing cement, fiber-mesh patching, EPDM or other flat-roofing material, roofing nails