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.
How many layers roofing felt.
Overlay a second layer of felt 2 to 3 inches and fasten it through the overlay so it secures the top of the felt underneath.
It s available in rolls that are 8m long and 1m wide with a thickness of 4 2mm mineral or 3 8mm sand.
The key to weatherproofing your flat roof is adding a total of 3 layers.
Of course how many rolls you need will depend on the size of the roof so ensure you measure correctly.
You wan walk over the roof to remove any air bubbles that may form.
Before adding the second layer though spread a thin layer of adhesive on the first layer using your trowel.
However in almost all areas it is not acceptable to install more than two layers of roofing on any commercial building.
Five best practices reasons for using roofing felt underlayment.
Align this layer with the bottom of the roof.
Add the second layer.
Installing the roofing felt does take care but can go very quickly.
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.
On most flat roofs such as epdm tpo or modified it is perfectly acceptable to two layers of roofing.
This felt or rubberized asphalt sheet provides an extra layer of protection between your shingles and your roof deck.
Thus you will repeat the earlier steps.
These thick layers of roofing felt are installed by heating the back of the felt with a butane torch and then carefully applying it to the roof.
A third layer of felt needs to be placed.
It helps reduce blow off by allowing your shingles to lay flatter and more uniformly.
So anywhere along the gable end that you can see the felt you ll see two layers.
On 4 12 or greater slopes the balance of the roof shall be one layer of 15 felt.
This will help the two layers adhere to each other.
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.
Additionally it prevents wind driven rain from getting under your shingles and causing damage to your roof structure or the inside of your.
Though the requirement is 2 layers 15 felt in my area northern california the roofers spec 30 whether for 2 layer low slope or 1 layer normal high slope.
There needs to be an overlap in the felt to help increase the water tight quality.
Paint a thin layer of adhesive over the first felt layer.
The first course starts with an extra 1 2 wide run.
You will be placing the second layer of felt over this.
For many years it was acceptable to put even the third layer.
