Like all roofs flat roofs require regular maintenance. Localised damage on the smooth surface of an asphalt or bitumen felt covering, e.g. splits and blisters can be patch-repaired with a repair kit. Repairing a flat roof is not difficult even for complete novices.
To deal with splits, first remove any chippings. Use a blow torch or hot air paint stripper to soften the roof covering so that you can scrape the chippings away. Then, before embarking on the actual repair work, clean the area and kill any moss and lichen with a fungicide or bleach. Take care when cleaning because the effectiveness of any repair work will depend on the adhesiveness of the surface when you apply any patches.
Use self-adhesive tape to repair the split. Most of them are suitable for use on all types of roof coverings. Fill a wide split with a mastic compound before taping. Apply the primer supplied over the area to be covered and leave for one hour. Peel off the protective backing of the tape and apply it to the primed surface. Where a short split has occurred along a joint, cover the whole line of the joint with tape. Press the tape down firmly and make sure that the edges are sealed.
Blisters in asphalt or felt roofs only need to be treated if they contain water or have caused the roof covering to leak. Press the blister to check if moisture is expelled. If so, it must be sealed with a patch.
To repair a blister in an asphalt roof, heat the area with a blow torch or hot air paint stripper. When it is soft, try to flatten the blister. If the blister is filled with moisture, cut the blister open and let the moisture dry out. Gently heat the asphalt again before pressing it back into place. Apply mastic into the opening before closing it. Finally cover the area with a patch of repair tape.
To treat a blister on a felt roof make two intersecting cuts across the blister and peel back the felt. You can heat the felt gently to make this easier. Clean the opening and let it dry. Then apply bitumen adhesive and when it has set a little, nail the covering back into place with galvanised clout nails. Finally, cover the repair with a patch of roofing felt glued on with bitumen adhesive or use repair tape. Cut the patch generously so that it laps all round.
A patched roof can be spruced up by applying a finishing coat of bitumen and chippings to create a more uniform surface area. If the surface covering has decayed you may have to re-cover the roof. However, a roof showing signs of general wear and tear can be brought back to life with a liquid waterproofing treatment. This consists of the cold application of a bitumen-based water proofer which is reinforced with a glass-fibre membrane. This should be done during warm and dry weather.
First clean the roof and kill any moss and lichen. Apply the first coat of water proofer with a broom and then lay the membrane into the wet material and stipple it with a soaked brush. Make sure the edges overlap by 5 cm or more and bed them down with water proofer. Apply three coats altogether. Let each coat dry before applying the next. Clean the brush with soapy water before each coating. When the last coat starts to set, cover it with fine chippings to provide a protective layer.
Repairing a flat roof is not difficult and within the capability of most people. By following the steps outlined above you can successfully repair a flat roof in very little time.