My house has a roof with 2 1/2:12 (11 degree) slopes. The manufacture says its OK to use asphalt shingles, but my contractor says it isn’t. Who is right?
There are some manufacturer (and even building codes) that will allow the application of asphalt shingle roof having the slope; however the National Roofing Contractors Association (NCRA) does not recommend shingles on slopes less than 4:12 (18 degrees). Asphalt shingle roof systems are watershedding and rely on gravity and roof slopes to effectively drain water off of the roof.