How Many Layers Of Roof Shingles Are Allowed In Montana

Most building codes allow up to two layers of organic or fiberglass asphalt shingles.

How many layers of roof shingles are allowed in montana. For fiberglass asphalt and organic shingles and a pitch under 4 12 as long as the roof structure remains sound you should be able to have two layers of shingles. However this depends upon the roof materials. Adding a second or third layer of shingles adds significant weight to the structure. Roofs between 2 12 to 4 12 pitch can use standard asphalt shingles but must have two layers of underlayment installed in the following manner.

Generally it is fine to have three layers of shingle but you should check this with your local building permit people and you should make sure that your roof and the rest of the structure have the strength to cope with the extra weight. Asphalt shingles typically can have one more layer added over the top two roofs total. For example cedar or tile roofs are only allowed one layer. Generally it is fine to have three layers of shingle codes but you should check this is the case with your local building permit people and you should make sure that your roof and the rest of the structure have the strength to cope with the extra weight.

Steep sloped roof products such as tile slate metal and shakes only allow one layer. On most flat roofs such as epdm tpo or modified it is perfectly acceptable to two layers of roofing. On top of the 19 inch strip of underlayment felt. For many years it was acceptable to put even the third layer.

Apply a 19 inch strip of underlayment felt on top of the ice barrier parallel to and starting at the eaves fastened sufficiently to hold in place. Regulations allow a maximum of two layers of shingles on a roof but experts say you shouldn t lay asphalt shingles over an existing roof. When it s time to replace your roof there are several factors that might lead your roofing professional to recommend adding shingles on top of your existing layers. In the portland area as of 2018 the current code allows up to three layers if the current layer is in good condition.