Bituminous Roof Minimum Slope

Modified bitumen membrane roofs must have a design roof slope of 1 4 12 or greater 2 slope.

Bituminous roof minimum slope.

All asphalt shingle roofs with a pitch of 4 12 or more have an underlayment of 15 lb. There are differing opinions as to the minimum slope for a roof but the generally accepted minimum is 3 12. The following table provides the minimum required allowable roof slope for each type of roofing material mentioned in the code. On occasion codes will permit aggregate surfaced coal tar roofs down to 0 125 inches.

The minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems. Some people recommend not installing asphalt shingles on slopes below 5 12 but a skilled roofer may well be able to make this work. The 2 12 number is rise over run or two units of vertical for every 12 units horizontal. Building elements a minimum design slope of 0 25 inches per foot is recommended for all membrane roof systems.

This 1 4 12 minimum roof slope requirement also applies to spray polyurethane foam spf roof. The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles. We can even help you find a professional to install it. Modified bitumen roofing minimum roof slope roof pitch r905 11 1.

Let owens corning help you determine when it is time for a new roof and then let us help you choose the shingles for your roof that are right for you. But shingle roofing is not watertight in the sense that standing water or wind driven water on a low slope roof can work its way up between the laps which is the reason for the minimum 2 12 slope. Shingles of all types need to have a slope to function properly. The minimum slope for a flat roof is 1 4 per foot or 1 4 12 but some owners or insurance companies require a minimum slope of 1 2 per foot.

That works out to about nine degrees if that works better for you. Experience the total owens corning roofing system and high quality roofing shingles. Asphalt shingles continue to be the most widely installed roof covering option in north america. The minimum requirement is 2 12.

Owens corning produces high quality asphalt coating asphalt sealants and adhesives for asphalt shingles. They provide excellent weather resistance great value and now more than ever a tremendous range of beautiful designs and color blends. This number corresponds to the number of inches of rise in a 12 foot run. Re cover with a second bituminous roof is generally permitted by building codes once surfacing gravel is removed spudded and wet areas replaced.

What is the minimum pitch slope of an asphalt shingle roof. This means for every 12 horizontal units the roof must rise a minimum of one fourth vertical unit.