How Much Roofing Underlayment Do I Need

These spots often get leaky first.

How much roofing underlayment do i need. Why do you need roofing underlayment. Rolls of felt are 36 wide x 144 long for 15 and 72 long for 30. 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. For roof pitches of 5 12 to 7 12 use a factor of 1 3.

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. Consider other underlayment options as needed such as rubber or tar products. 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. Fifteen pound or heavier felt underlayment is required by code in some areas.

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. Minimum overlap guidelines are set by the manufacturer. Inquire at the hardware store regarding the amount of underlayment nails required. 1square of roofing covers 100 square feet of roof a bundle is 1 3 of a square.

Always use 1 in 2 5 cm nails. If you are installing synthetic underlayment 6 inch overlap is sufficient. The vertical overlap should be at least 2 feet or 24 inches. There is a direct connection between membrane performance and proper application.

If your roof pitch is 3 12 or 4 12 multiply by 1 25. For a new roof you will also need the same amount of underlayment. Roofing underlayment or felt is usually required for the ul fire rating to apply since shingles are usually tested with underlayment. Underlayment usually comes in rolls of 4 squares each.

Multiply the total area determined in step one by a correction factor to account for the roof pitch. This correction factor will take into account the greater area of the roof due to the pitch. So in the gable roof example above you would need 240 squares of underlayment. The underlayment protects the edge of the roof deck from water damage.

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. It s a moisture barrier. No underlayment is needed if you are applying shingles directly over an existing asphalt roof. Roofing underlayment provides your roof with an extra layer of protection that.

While it is possible to estimate the amount of necessary materials using only the total roof area measurement as can be seen from the table depending how large the pitch of the roof the actual area of the roof can differ by up to 2 236 from the measured total area at a pitch of 24 12. Rubberized asphalt roofing underlayment should be added at valleys and around roof protrusions.