Shingling The Steep Slopes Of Mansard-Style RoofsOliver Olinger, Writer
Construction projects on mansard/gambrel-styled roofs require specific application methods that differ a bit from the standard methods used on normal hip-and-gable-style roofs.
The steep slopes of mansard roofs reduce the effectiveness of factory-applied adhesives and fasteners, especially in colder or shaded areas, and therefore roofers must take additional steps to ensure proper installation.
If the slope of a roof exceeds 60 degrees (21:12 slope pitch), asphalt roof cement that complies with ASTM D4586 should be used in addition to fasteners.
Secure the shingle to the roof deck with fasteners as specified in Atlas’ shingle installation instructions. (Bear in mind that Atlas requires six nails per shingle when fastening shingles to steep roofs.)
When installing laminate or architectural shingles, apply six quarter-sized dollops of asphalt plastic cement under each shingle. Position the dollops about 1 inch up from the bottom edge of the shingle and space them equidistant across the shingle with the two outermost dollops positioned 1 inch from each outer edge. Press the shingles into place.
The procedure for installing three-tab or strip shingles is slightly different. Roofers will still need to apply six quarter-sized dollops of asphalt plastic cement under each shingle. Two quarter-sized dollops should be placed under each tab with one quarter-sized dollop placed 1 to 2 two inches from each side edge of the tab near the bottom. Press the shingles into place.
The plastic cement should not be exposed when the shingles are pressed into position. Once the cement sets, the shingle installation will be complete.
Remember that excessive use of roofing cement can cause shingles to blister. To avoid problems, follow installation guidelines exactly.