If you have an asphalt open valley, you may find that you have problems with leaking along the surface of your roof. This can be from a number of causes, including loose shingles and even holes in the roof, but once you have ruled all of these out, you may be left with the idea that the problem is your open valley. These are areas where parts of the house are connected to each other, and the roofs intersect. This can happen if you have had an extension, for example. Holes within an open valley can cause water to leak into the attic, or even into the home. In order to fix the open valley, you will need to carefully inspect the hole, and then repair it.
Step 1 - Locate the Leak
You should be able to locate the problem by inspecting your valley for holes. Look the entire length of the joint, as you will need to find all of the possible holes through which the leak is emerging in order to successfully plug them. Once you have found the hole, you will need to remove all of the asphalt over the surface of the hole. Use a brush to sweep away loose asphalt, and then either cut around the remaining roof material, or remove the metal surface of the valley. This will be replaced.
Step 2 - Add Your Flashing
You will need to lay out your flashing on the roof, to make sure that it is a suitable length. If it is not, cut it down until you are satisfied that you have a suitable length for your flashing, and then lay it down on the surface of your roof valley. You should be able to secure the valley with a layer of caulking. This caulk should be specially designed for roofs, including being waterproof and quick-drying. If you can't manage to find the right sort of caulking that this would allow, try laying the flashing using a hammer.
Step 3 - Add More Caulk
Once the flashing is in place, you need to lay another layer of roof cement over the surface of the flashing, and fix the roof material that you removed earlier into place. You should make sure that all the surfaces of the flashing are covered in caulk, and that there is a good layer around the edges, in order to completely keep out water. Leave to dry.
Step 4 - Replace the Asphalt
Take the asphalt which you had previously removed from the roof valley, and lay it back into place. You may need to use the hammer to push it back into place around the flashing, but you can then just place the loose asphalt on the surface. Leave the entire area to settle into place, and then check your roof for leaks the next time that it rains.