Prime the repair area once the surface of the patch area is free of all dust debris and moisture apply the liquid asphalt primer to the roof surface with either a brush or roller.
How to repair a roof with tar.
Leaks and other damage to tar and gravel flat roof are repaired by patching the roofing membranes and a temporary roof leak repair may be required before a roofing contractor can create a more permanent fix.
You may need to cut out a narrow strip.
If the cost of the roof repair is truly bothering you consider making your own temporary repair by tacking a tarp over the roof or cutting up some sheet metal into shingles and using these to patch the roof.
Cut patch and coat.
Use a utility knife to cut a slit in a bubble or lift up the two sides of a crack.
Fill hole with cement.
Rubber coat 57 roof tar.
Press the flaps from the cut portion into the tar and then spread another layer of tar on top of the flaps.
Spread a layer of tar on the roof beneath the spot you have cut away.
Allow the primer to flash off so that there is no excess primer on the surface of the roof.