Wind driven rain or snow can trap water under your shingles putting your roof deck and inner residence at risk of moisture.
Two layers of felt on roof.
It provides structure by tying.
Two layers of shingles trap more heat which in turn damages the shingles and shortens the life span of the roof.
You can cover the surface of the felt with gravel for added strength.
Most often made out of plywood this roof layer is installed over the framing in a typical roof install.
This will help the two layers adhere to each other.
I am aware of the best practise of at least one layer of underlay nailed to the deck before a cap sheet is glued to the top with cold adhesive.
You will follow the same process as in step 2 for the last layer.
Saving on the initial shingle installation doesn t solve the long term cost of adding a second layer of shingles.
If i were you i d at least follow up with that roofer on why they chose to spec 2 layers felt just for piece of mind and in case he turns out to be the better roofer or not.
Thus you will repeat the earlier steps.
Cover the edges of the roof with strips of felt before laying out the final layer.
Add the second layer.
Apply another layer of adhesive to the top for maximum waterproofing.
The first course starts with an extra 1 2 wide run.
Here are the layers of a roof in order of application bottom to top.
Five best practices reasons for using roofing felt underlayment.
Why use roofing felt paper.
I have been supplied with way too much felt.
On roof slopes of 2 12 to 4 12 the remainder of the roof shall be two layers of 15 felt applied in shingle fashion or 1 layer of ice dam protection.
Roofing felt offers an additional layer of protection against the elements.
Before adding the second layer though spread a thin layer of adhesive on the first layer using your trowel.
It didn t come with any underlay but i have worked out i could felt the roof twice with the cap sheet felt they have supplied.
Assuming your roofing contractor is using standard 36 wide 15 roofing felt double coverage means that each layer of felt put down across the roof laps 19 over the upper half of the previous course.
The key to weatherproofing your flat roof is adding a total of 3 layers.
It provides backup protection in the event of ice or water damage.
So anywhere along the gable end that you can see the felt you ll see two layers.
For decades roofers have fitted a layer of felt over a roof s sheathing or roof deck before installing shingles.
