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I’ve been watching the re-roofing of a 75+ year old house across the street. The existing roof consisted of a layer of comp shingle and a layer of sawn cedar shingles on 1″ x 8″ sheathing with 1″ spaces between boards. The roofers stripped the comp shingles, cut out about a 6″ strip along the edges, applied osb to the edges, then the drip edging and paper. Architectural comp shingles were then applied. Frankly, the new roof, like the old, looks like hell, with horizontal ridges visible where the edges of the cedar shingles telegraph through. Now the question – is this a normal practice for redoing this type of roof? Would stripping the old wood shingles off and applying sheathing, but leaving the existing 1″ x 8″s in place, be a preferred practice? Is shingle warranty affected by doing it this way?
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don... this roof you describe is so unusual that there is no such thing as ""normal practise""
if they stripped the wood shingle they would have had to lay one inch strips between the "skipped sheathing""
or over laid the skipped sheathing with 3/8 or better ply...so they probably made an economic decision.. hopefully they passed the savings on to the homeowner..
or discussed the options with them..
*The original sheathing may have been "green" and shrunk when it dried,leaving 1" gaps."Skip" sheathing has gaps larger than 1",at least that is local practice around here. A good job would have entailed stripping the roof down to the sheathing and applying 1/2" plywood over it.
*Yes this is commonly done, but that doesn't make it rightYes it will affect the warrantee because where the shigle is not fully supported by sheating behind it it can break from walking it or hail stones easily. Also the air space thus created will have excessive heat buildup at the back of the shingle, leading to premature failure. To keep the ugly ridge lines from showing as headlaps build out of synch with the previous cedar shingles the exposure of the new should have been adjusted to allow the top of the new comp shingle to butt the bottom of the old cedar. Since the skip sheathing was 8" with a one inch gap (very common in the old days) they are at 9" on center. This would allow for 4.5" exposure on the new shingles. They are designed for 5" exposure so the cost would increase by 10% for waste. Some shingles are now made to metric sizes at 5-5/8" exposure so the waste factor would be greater. In doing this there is a greatre likliehood that the sealdowns wouldn't work as well on standard 240#ers because the strip is on the face of the shingle at midline. With heavier arch grade comps the seal strip is on the back bottom of the shingle and would be located properly, regardless of adjusting the exposure.When roofing in the Southwest, I saw this practice regularly and always made two estimates, discussing with the homeowner the pros and cons of both approaches. In the face of economics and prevailing opinion, the cheaper option was choosen more often than I would have prefered.The correct way is to remove all the old shingle material of both layers, replace and patch bad sheathing or layer it with plywood(best option in my mind) and then apply the new shingles. Labor to install is much faster on a smooth surface than on rough old shiongles so this helps overcome some of the cost of new sheathing layered on.
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I've been watching the re-roofing of a 75+ year old house across the street. The existing roof consisted of a layer of comp shingle and a layer of sawn cedar shingles on 1" x 8" sheathing with 1" spaces between boards. The roofers stripped the comp shingles, cut out about a 6" strip along the edges, applied osb to the edges, then the drip edging and paper. Architectural comp shingles were then applied. Frankly, the new roof, like the old, looks like hell, with horizontal ridges visible where the edges of the cedar shingles telegraph through. Now the question - is this a normal practice for redoing this type of roof? Would stripping the old wood shingles off and applying sheathing, but leaving the existing 1" x 8"s in place, be a preferred practice? Is shingle warranty affected by doing it this way?