Proper Roofing Underlayment Installation

Ideally the roof covering material would be installed as soon as possible but in reality the roof may be protected by only the underlayment for days weeks or sometimes months.

Proper roofing underlayment installation.

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. Synthetic roofing underlayment is to be laid horizontally parallel to eave with printed anti slip side up starting at the bottom of the lowest roof eave with a 1 5 underlayment overhang at the eave covering the pre installed eave drip edge. Roof slopes greater than 4 12 require only one layer of underlayment. Minimum overlap guidelines are set by the manufacturer.

Center a minimum 610 mm 24 wide minimum 28 gauge pre finished galvanized metal valley liner in the valley and fasten with only enough nails to hold it in place nailing at the edges only. It must be covered with waterproofing membrane usually roof felt also. For three tab shingles place two quarter size spots of plastic roof cement under the lower corners of each tab as shown in figure 2 7. Overlap each metal piece by at least 150 mm 6 and use asphalt plastic cement under each section of overlap.

Roofing underlayment roofing felt requirements. There is a direct connection between membrane performance and proper application. Underlayment in high wind areas i e where wind speeds are 110 mph or greater must be secured with corrosion resistant fasteners spaced no more than 36 inches apart. Felt details for various roof slopes amp.

With laminated shingles place four to six quarter sized dots spaced evenly about one inch above the bottom of the overlapping shingle. Roof underlayment prevents the roof deck from being exposed to the elements before or while the roofing material is being installed.