It is advisable to use plastic cap nails to fasten down the underlayment with 12 inches on center spacing at the top and bottom of each course.
How much roofing underlayment do i need.
Inquire at the hardware store regarding the amount of underlayment nails required.
If you are installing synthetic underlayment 6 inch overlap is sufficient.
The roof deck should be sound and level before laying the underlayment.
The average roll of 15 pound roofing felt covers about 400 ft 2 or 4 squares while the average roll of 30 pound roofing felt covers about 200 ft 2 or 2 squares.
It s a moisture barrier.
Multiply the total area determined in step one by a correction factor to account for the roof pitch.
The nails should be 12 inches 30 cm apart along the edges and 24 inches 61 cm apart in the middle of the underlayment strip.
1square of roofing covers 100 square feet of roof a bundle is 1 3 of a square.
The vertical overlap should be at least 2 feet or 24 inches.
Rolls of felt are 36 wide x 144 long for 15 and 72 long for 30.
Minimum overlap guidelines are set by the manufacturer.
Gcp applied technologies grace ice water shield roofing underlayment requires side laps to be a minimum of 90 mm 3 5 in and end laps a minimum of 150 mm 6 in.
Roofing underlayment or felt is usually required for the ul fire rating to apply since shingles are usually tested with underlayment.
Fifteen pound or heavier felt underlayment is required by code in some areas.
For a new roof you will also need the same amount of underlayment.
No underlayment is needed if you are applying shingles directly over an existing asphalt roof.
This correction factor will take into account the greater area of the roof due to the pitch.
These spots often get leaky first.
Consider other underlayment options as needed such as rubber or tar products.
Get the square footage of roof and divide it by 100 and it will give the number of squares you need and for every decimal number over 3 buy a bundle to achieve the amount of material.
So covering 240 squares would require 60 rolls of underlayment.
There is a direct connection between membrane performance and proper application.
For roof pitches of 5 12 to 7 12 use a factor of 1 3.
So in the gable roof example above you would need 240 squares of underlayment.
Underlayment usually comes in rolls of 4 squares each.
Always use 1 in 2 5 cm nails.
The underlayment protects the edge of the roof deck from water damage.
Underlayment should cover the entire roof deck.
Why do you need roofing underlayment.
Rubberized asphalt roofing underlayment should be added at valleys and around roof protrusions.
