Materials you'll need:

• Flashing
• Flashing tape
• Roofing cement
• Sealing compound
• Solder or plastic metal
• Bituminous paint if required.

Tools you'll need:

• Tin snips
• Caulking gun or putty knife.

Flashing is the term used to describe the flat strips of metal sheeting used at sills, joints between gutters and tiling or roof sheeting, and around waste pipes and chimneys. It is designed to divert rainwater away from these joins.

Two of the most common materials used are aluminium and sheet lead. Sheet lead is very efficient but expensive. Its own weight ensures it stays securely in place.

Aluminium flashing, while also efficient, is more prone to move with movement in the building. The aluminium facing protects the bituminous material underneath the flashing tape, which does the sealing. Because the tape is also self-adhesive, it is very easy to apply to repair gutters and flashing and many other jobs.

For larger jobs, you should cut a patch of flashing to fit. It can be cut to size with tinsnips and fixed in place with roofing cement, rivets or self-tapping screws.

The flashing should be checked regularly to ensure it stays in good condition. Any parts that are cracked, torn or perished should be packed with a suitable sealing compound.

These compounds are sold in cartridges for use with a caulking gun, or in packs, which can be applied with a putty knife.

Small holes in metal flashing can also be repaired by first cleaning the area then sealing with solder. Silicon sealers.

If the masonry is damaged and the flashing has come loose, chip out the damaged masonry and blow out the debris then push the metal flashing back into position and fill the crack with a suitable sealing compound.

When replacing flashing, remove the old flashing first and use it to cut out a new piece to the same shape. Chisel away the old compound that held the flashing in place and replace the flashing, securing it with roof cement. Ridge flashing can be fixed in place with either roof cement or mortar. After the roof tiles are back in place, all exposed nail heads should be covered with a sealant.

When flashing from a brick wall to a tile roof the flashing material (usually lead) must be inserted into the brick joint. This is usually done by the bricklayer and later folded down over the tiles by the roof tiller. However, if you need to insert flashing after your building is up you, will need to rake out the mortar to allow insertion of flashing, and re-mortar or seal any cracks.

Bituminous paint. Flat roofs are frequently sealed with bituminous materials, which are affected by sunlight after a few years. These can be given a longer life if they are painted regularly with a bituminous paint designed for the purpose. If the flashing has been neglected and leaks are starting to be a problem, the only way to track down the leak and repair it may be to remove the flashing material, fix the leak and replace with new bituminous flashing. Once repaired, it should be maintained with regular coats of bituminous paint.

Valleys.
Valleys are the deep junctions where two roof lines join. The valleys are usually preformed from pressed steel or other materials and are bought in lengths as required Where the roof tiles come together in a tight join, you can mend leaks by cutting aluminium flashing into 30Omm squares. Bend it diagonally and bend the resulting triangle so it forms two sides of a pyramid. These shapes are inserted under the tiles and pushed up as far as they will go, starting with the lowest course of tiles and working upwards. Holes in valleys can also be mended with a patch of flashing cemented in place.

Caulking.
Another area that may require attention is the exposed joints where two different materials are joined on the exterior of the building. The joints between window and doorframes, and brick and tiles are examples. The joins are made waterproof by caulking with a sealing compound forced into the cracks from a caulking gun. Any areas of caulking that have dried out or are damaged, should be repaired with caulking compound.