Small cracks or splits with no bubbling of roof surface
If you find small cracks or splits and the surface still appears flat, then the surface can
be easily repaired using bitumen mastic spread evenly over the area. Self-adhesive repair
tapes are also available for this type of repair. However make sure that the surface is
thoroughly clear of debris and cleaned carefully before application. This is because the
effectiveness of the repair is only as good as the seal between the spread and the surface.
Choose a dry, warm day to repair the surface. Once the bitumen mastic is smoothly in
position, apply more compound to the surface to seal completely and cover with some gravel
chipping to match the rest of the surface. The chipping compound, such as limestone, gravel
or granite on top of the layers of felt, strengthens the surface further. The idea is for
the surface to reflect rather than absorb sunlight, thus helping to protect the felt.
Cracks and signs of bubbling
If the cracks are also showing signs of bubbling, then water could possibly seep through the
surface. Moisture has already penetrated under the felt. When the roof has warmed in the
sun the felt swells in the heat causing blistering on the surface. Choose a dry, warm day
to make a cross shaped cut in the centre of each bubble and open up to allow the area to dry
out completely. Allow some drying time, before using a cold bitumastic compound to bed the
felt back into position. If necessary, the area can also be nailed back into position with
galvanised clout nails. Once the felt is back in position, apply more compound to the
surface to seal completely and cover with some gravel chipping to match the rest of the
surface. The chipping compound, such as limestone, gravel or granite on top of the layers
of felt, strengthens the surface further. The idea is for the surface to reflect rather
than absorb sunlight, thus helping to protect the felt.
No cracking, no bubbling, but signs of dampness
If there is no evidence of cracking or bubbling, yet there are signs of dampness on the
ceiling below, check the flashing. The flashing strip should be set against the wall and be
totally watertight. This area can sometimes come away from the wall allowing water to
trickle below the surface of felt. Choose a dry, warm day to repair the roof. Take the
flashing strip off by prising it away from the wall. Clean the area by raking out old debris
and mortar. Use a ready mixed mortar if only a small amount is required. Brush away any
dust or grit and dampen the joists with an old paintbrush. This will stop the mortar drying
too quickly and cracking. Use the mortar to fix the flashing strip into position and
re-point the joist.
