Roofing/Roof pitch

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Question
What is your recommended minimum pitch on a laminate shingle?

Manufactures say up to 3/12 is ok. But they will only warranty leaks with a default shingle.  

I have a 3.5/12 roof and have discovered after 10 year old roof a issue where water is getting up under the single with strong winds.

Answer
For a laminate shingle I would install it so it can be seen so 6:12 and up. Shingles are normally installed on 4:12 or greater. Less than 4:12 is called low slope territory and membranes are normally installed. However you can install regular shingles but there are precautions to take. The whole roof must be covered with an eave protection membrane to shed the water. Normal 3-tab shingles are installed and all tabs must be adhered with a dollup of plastic cement.
Why? The low slope will hold ice and snow all winter so the eave protection will keep the water out. Secondly the dollup (dab) of plastic cement under the tabs will stop the shingle from lifting due to freeze that cycles when the roof holds snow. 3-Tab because of price.

Now the down side, warranty from shingle manufacturer may only be 10-12 years regardless of 3-tab (25 year) laminate (30-50 years) or even a lifetime shingle. Recommend low slope self-adhesive modified bitumen membrane from Certainteed since the color also matches their shingles.

Hope this helps.
D. John

Roofing

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D. John Henderson

Expertise

My 33 years in the building science business has involved air barriers, waterproofing, and flat & steep slope roofing systems.

Experience

My roofing encompasses commercial systems (BUR, mod-bit, single-ply) and residential applications (asphalt shingles, cedar shingles, slate and metal. I am cognizant of code stipulations in regards to FM and UL for commercial roofs.

Education/Credentials
Attended numerous courses offerd by Roof Consultants Institute, Roofing Industry Educational Institute, Factory Mutual Research Corporation, University of Wisconsin, and BURSI. Lectured for RCI and mentored at a local university for a Building Science Certificate.

Past/Present Clients
Government, commercial businesses such as The GAP, hospitals, school boards as a roof designer.

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