Low Slope Metal Roof Underlayment

Gcp applied technologies grace ice and water shield 36 in.

Low slope metal roof underlayment.

Ft coverage sbs modified asphalt polyester self adhered low slope roofing roll in black model lb323235. I have found the proper roof but the underlayment options and guidance has been scattered. Guide to roofing underlayment installation on low slope roofs with asphalt shingles. 1 cover the entire surface with a self adhesive flashing membrane such as grace ice water shield there are many equivalent products.

Asphalt shingles can be used on roofs with a slope of 2 12 to 4 12 if double coverage underlayment is used. Low slope metal roofs have simple geometries and are easier and less expensive to install that medium to steep slope roofs. Once the high temperature ice and water shield has been laid down you can now add the second underlayment layer. A metal roof mechanically seamed crimped and butyl injected at the seams designed to handle low slopes as low as 5 12.

There is only one category of metal roof systems used in low slope applications structural metal panel. Asphalt saturated felt along the eaves and lap succeeding courses by 19 inches as shown in figure 2 3. Minimum metal roof slope depends on the roof profile building design climate and site location. If the roof slope is below 3 12 pitch see our previous post on how to determine a roof s pitch the entire roof should be covered but only if the roof is conventionally vented cold roof construction.

The membrane will outlast the shingles and seal around all nail penetrations. Also if you live in a climate such as the up in michigan and routinely get over a foot of snow standing on the roof you may want to consider it. Structural metal panel roof systems can be used for low slope roofs because of their hydrostatic or water barrier characteristics. Then apply standard asphalt shingles over the membrane.

In fact many synthetic underlayments are designed for specific roofing materials so be sure to check and verify beforehand. Determining which panel is the right choice for the slope on your project will depend on the manufacturer s minimum slope factor for that specific panel profile. Start with a 19 inch strip of 15 lb. These advantages and disadvantages do not apply to granulated synthetic underlayment as it is not to be used directly under metal roofing.

At sheffield metals we also recognize low slope as 3 12 and below. A low slope roof is defined in the industry as a roof that has a pitch equal to 3 12 or less. Some shingle manufacturers require ice and water shield on very low sloped decks between 2 12 and 4 12. Low slope roofs are not totally flat their roof slope generally ranges from 1 4 12 to 3 12.

For a low slope residential roof there are two main options. My roof at lowest is 75 12. Lower slopes for low slope standing seam metal roof applications strictly peel and stick underlayment is a better choice. Roll self adhered roofing underlayment 225 sq.