Roofing: Skylight Flashing and Vertical Wall Flashing

Metal Valleys

Once you have finished installing the metal valleys to your roof, whether this is over existing shingles or on a new or stripped roof deck, it is time to finish the valleys. This can be done in one out of three ways. These three ways are called open finish, closed-cut finish and the woven finish. Before I tell you a bit more about these finishes, let me give you a quick break down on how to install the metal valleys.

  • Using a 15 pound roofing felt, lay a 36 inches wide panel along the length of the valleys
  • Nail down the metal valleys using 1 ¼ inches galvanised nails at 12 inches intervals (this should be done on both sides and about 1 inch from the outer edges)
  • Spray paint the metal to protect it and to make it blend with the roofing materials purchased (make sure the paint is rust-resistant)
  • It is now time to finish the valleys!

So, as mentioned before, there are three different ways in which you can finish your valleys and what type of roof you have will play a part in this. If you happen to have an asphalt roof, you can choose whatever finish you prefer but if your roof is wood or tile, only two out of the three ways is suitable and these two are the open or close finish. I will now tell you a bit more about the open finish.


Open Finish

If you are choosing the open valley finish, whatever shingles you are using, asphalt, tile or wood, should be trimmed along the outer edges of any flashing. The best way to do this is to snap two chalk lines on either side of the valley centre. Start the chalk lines at the ridge and at about 3 inches from the valley centre, making sure to mark both sides of it. As you draw them towards the eave, make the lines slant slightly away from the centre of the valley. This is to allow for debris and water to move more easily towards the gutter. The slant should be about 1/8 inch per foot so this means that if the valley is 10 feet long, it should start at 3 inches from the top of the valley centre and it should end at just over 4 inches from the valley centre at the eave. It is best to trim shingles and tiles at the chalk line and the best way to do this is by using a utility knife for asphalt shingles, a circular saw for tiles and a hand saw or even a so called ‘roofer’s hatchet’ for wood.

roofers hatchet

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