Slate roofs can last up to 200 years if they are installed properly. Venting a slate roof on a ridge during the installation is the easiest way to achieve the required ventilation of the attic. Check your local codes to determine the ratio between vents and attic space. Installing vents on an existing slate roof is more involved because secured slate may be knocked loose. These vents install on the sloped part of a roof between the pieces of slate.
Determine the position of the vent on the slate roof. For the best results, install the vent on top of two adjoining slate shingles.
Cut the two pieces of slate according to the size of the "vented" part of the vent. Slice the felt with a razor knife in the shape of an upside down "T" and fold it back.
Cut a hole in the sarking board, if present, to match the size of the "vented" part of the vent with a hole saw. Set the slate vent in place using the holes in it to line it up with the slate on the roof.
Secure the front of the slate where the vent sits with a copper disc rivet. Be certain that enough of the slate overlaps the top of the vent to prevent water damage.
Install furring strips along both sides of the opening in the ridge of the roof with 2 1/2-inch hot-dipped galvanised nails. This is for supporting the slate.
Secure plastic ridge vent material to the furring strips with the galvanised nails. For the best results, use a low profile ridge vent.
Place the first piece of copper flashing on the end of the ridge and let it hang over enough so you can fold it down to hide the furring strips. Secure it to the furring strips (through the ridge vent) with 2 1/2-inch copper nails.
Secure slate ridge over the flashing with 2 1/2-inch copper nails. Place the next piece of flashing on the ridge so one end overlaps the slate ridge you just installed and secure it in the same manner as before. Repeat this until the ridge is covered.
Caulk the joints of the ridge slate with clear silicone caulk.
Install a short lightning rod on one end of the ridge.
Do not drive the nails any harder than necessary to hold the slate in place to prevent leaking.