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Low pitch roof waterproofing - Hudson Valley

robbmc's picture

Largish split level ranch house (4200 sq ft) built in 1964. 4 in 12 pitch to most roofs but 2 in 12 over indoor pool. New screened porch roof to be 1 in 12. The existing roof (a mix of 3 tab and 1 tab shingles) needs replacing. My thoughts are to strip down to the ply decking and cover 100% with GRACE ICE & WATER SHIELD® after replacing all questionable decking. Our preferred roofing would be standing seam metal but our budget (for an extensive renovation) requires that we use a less expensive material. Simple gable roofs with no hips or valleys.

We are currently looking at asphalt shingles as my wife really dislikes the apperance of roll roofing on the two low pitch roofs whch are prominent in the view from the deck off her studio. We have heard that 3 tab shingles drain better in low pitch conditions than the current architectural style. We are OK with the look but are surprised at contractors wanting more money to install the 3 tabs vs the HD style.

R-38 batt insulation is currently on ceiling so I am not imagining ridge vents BUT I am interested in the potential upside of spray foam to the underside of the roof. 

Thanks in advance for any and all input.

Robb

2/12 is not enough pitch for (post #216305, reply #1 of 3)

2/12 is not enough pitch for shinges without some special prep. You'll need at least 2 layers of Weather Guard or another approved secondary membrane under the shingles. In that case the shinges become almost cosmetic. 

Spray foam will totally seal your roof and glue the whole thing together..

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

100% Coverage (post #216305, reply #2 of 3)

florida wrote:

You'll need at least 2 layers of Weather Guard or another approved secondary membrane under the shingles. In that case the shinges become almost cosmetic. 

florida wrote:

You'll need at least 2 layers of Weather Guard or another approved secondary membrane under the shingles. In that case the shinges become almost cosmetic.

What do you think about the idea of 100% coverage of Ice & Water Shield? 

I ceand Water Shield is a (post #216305, reply #3 of 3)

Ice and Water Shield is a secondary membrane made for roof edges and valleys. Weather Guard and similar products are made to cover the entire roof. They are probably the same thing but down here in Florida we don't use Ice and Water at all but do typically cover the entire roof with Weather Guard or a like product. My house is being shingled as I write and it all has the secondary membrane on it, in my case it's another brand but serves the same purpose.  I wouldn't do without it.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.