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. Steep sloped roof products such as tile slate metal and shakes only allow one layer. Adding a second or third layer of shingles adds significant weight to the structure. The soundness of the building you re re roofing is another consideration.

In the portland area as of 2018 the current code allows up to three layers if the current layer is in good condition. 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. On most flat roofs such as epdm tpo or modified it is perfectly acceptable to two layers of roofing. 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.

Asphalt shingles typically can have one more layer added over the top two roofs total. However this depends upon the roof materials. One of the largest benefits associated with double layering as opposed to stripping and laying a complete new set of shingles is simply saving costs. 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.

On top of the 19 inch strip of underlayment felt. 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. For example cedar or tile roofs are only allowed one layer. 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.