Vent Pipe Flashing and Drip Edges

Vent Pipe Flashings

It is important to remember that even ventilation pipes on the roof will have to have flashings installed around them. The best time to have them installed is when the roofing materials go down. The reason for this is that the lower part of the flashing should sit over the shingles whilst the upper part of the flashing should later be covered by shingles. You can make your own flashing from asphalt roll roofing or sheet metal but both plastic and metal flashings can as easily be bought from your local roofing supply company. Whatever way you go, remember that vent pipe flashings should have a large base to carry away any water. This means that the seals between flashings and vent pipes will have to be completely waterproof and secure.

Vent Pipe Flashing

Start by measure the diameter of your vents before taking any further action. The base vent flashing should be squared and every side 12 inches larger than the vent diameter. If you choose to make your own flashing for the vent pipe, cut out a square of roll roofing or piece of metal. Draw a line 4 inches above the bottom edge and line it up with the lower side of the pipe before drawing a mark on the upper side of the pipe. Put the flashing down on the lower side of the pipe, taking care to line up the middle of the flashing with the middle of the pipe. Make two further lines even to the two sides of the pipe. The resulting middle rectangle will show you where to cut the opening for the vent. Once cut open, trowel on plenty of plastic cement at vent base and then install the flashing on top. Add more cement around the vent pipe and cut any further roofing materials to fit above and to both sides of the flashing.

Vent Pipe Flashing1

Drip Edges

One thing that eaves and rakes have in common is that they both require drip edges. Drip edges are there to prevent the water from seeping through to under the roofing material as it is flowing off the roof. When it comes to the eaves, the drip edges should be installed underneath the roofing felt and when it comes to the rakes, they should be installed on top. I would use galvanised roofing nails (1 ¼ inches) and fasten them to pre-formed flashings or alternatively, you can use a galvanised metal or aluminium strip along eaves and rakes. The strip should be about 5 inches wide and you will need to leave an overhang of about 2 inches. Hammer the nails down 1 ½ inches below the upper edge and roughly about 10 inches apart. The 2 inch overhang extension should be bent downwards at the end.

Drip Edge


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