Repairs to flashings | roof repair

The repairs to flashings for the main roof are intricate. Where a two-way roof meets an end wall, for instance, a stepped flashing is required to follow the slope of the roof. Much more complicated is the arrangement round a chimney stack, with an apron flashing on the lower side, stepped flashing on perhaps two others, a back gutter, and perhaps even soakers – small pieces of lead, copper, zinc, or bituminous felt used to weatherproof the joints between these or bituminous felt. Given all these complications, and considering the difficulty of access, it is perhaps better to employ a professional when renewal is necessary, although you might feel confident about tackling the minor repairs of flashings. Renewing a straight, horizontal flashing, especially on the roof of a small lean-to building where access would be easy and is certainly much simpler. For the new repairs to flashings, you could use lead, but bituminous felt is less expensive. Remove the old flashing, and rake out the mortar joint to a depth of about 25 mm. Clean the brickwork and tiles, a wire brush is suitable for this.

Roof FlashingIf there is a small mortar fillet where roof and wall meet, inspect it for damage, and repair it if necessary, as described in the next section. Bend the flashing over then push it into the join and wedge it there. Next bend it over the tiles, sealing it with mastic to stop it from curling. Then repoint the mortar joint. You may prefer to use a proprietary flashing, which is sold in home improvement stores and builders merchants. The method of applying such flashing strips varies, so always follow the manufacturer’s instructions. These strips usually have a backing tape, which you peel off to reveal an adhesive. Some are in grey plastic, to simulate lead; others have an aluminum foil covering. The fault in a flashing may not be so drastic as to call for complete renewal. For instance, the repairs to flashings itself may be sound, but the mortar in the joint might have deteriorated, causing the flashing to fall away. In that case, rake out the joint, put the flashing back into place, and re-point. Cracks in an old flashing can be sealed with bituminous mastic. The method for doing this is as for dealing with cracks in a valley.


corrugated plastic roofing – panels and sheets

Corrugated plastic roofingThe roofs of many home extensions designed as sun rooms and conservatories, but not intended as habitable rooms, are covered with corrugated plastic roofing panels or sheets. Corrugated plastic is a long-lasting material, but leaks can develop. Physical damage to the plastic can be caused by heavy objects being thrown or blown on the roof during a gale. A heavy fall of snow cascading from the main roof could also cause cracks lf this occurs, take off the damaged sheet and replace it with a new one. Take a little of the old sheet with you when you go shopping to make sure the profiles match exactly. When fitting the new panels and sheets, remember that each should overlap its neighbor by two corrugations, and that overlaps between the ends of sheets should be at least 150 mm. Sealing washers may be defective. The sheets are fixed to wooden rafters with screws or nails, or to iron rafters with clips. Such fixtures should have a nail cap and a rubber or plastic washer between the head of each nail and the sheet, to stop the rain getting through. These may have deteriorated, or might never have been fixed in the first place. Replace any defective washers; install them where they are missing. You can buy replacement caps and washers, as well as nails if these need renewing. The flashing may have come adrift from the wall, or be defective. You may be able to re-fix loose flashing back in the mortar joint as described in this chapter. If the flashing is defective, buy and fit a replacement. Flashing specifically for corrugated plastic roofing materials is available.  Support for the sheets may be insufficient, in which case they can buckle, causing gaps through which rainwater can penetrate. The only remedy is to provide extra support, and replace the affected sheets.