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mccloud
protecting asphalt roof

My house is built into a hillside, such that the roof of the garage serves as the deck next to the living room. The garage roof was metal, and over time developed rust and leaks, so I ripped it up, replaced underlaying damaged wood, recovered with new plywood, then used several layers of tarpaper along with roofing sealer, with a top layer of the heavy asphalt shingle type material that comes on a roll. But since that is not an attractive surface to walk on or set patio furniture on, I set 2x 4s on edge, on 16" centers, then covered with manmade plastic/wood decking. I was pleased with the result. But after 7 years I have leaks again, so lifted some of the decking and was surprised to see that the 2x4's had cut through the asphalt shingle material at several places. I'm scratching my head about what to use to prevent the 2x4s from repeating the cutting over the next 7 years. I've been told that if any weight, like patio chairs & table, is put onto rubber roofing membrane,that voids the warranty. So I'm looking for a good idea as to how to prevent future damage to the roof.

HoustonRemodeler
Re: protecting asphalt roof

I have seen foam blocks used as a slip sheet between the roofing and the wood. This is typical when setting HVAC units which can weigh quite a bit.

There also roofing deck systems used on commercial roofs to allow humans to have a picnic, smoking, or sun tanning space.

dj1
Re: protecting asphalt roof

Here's a creative idea: sinc all you need is something to distribute the weight on the 2x4s so that they don't rub on the roof material, why not lay 2 freestanding layers of shingles under them, with no nails and no tar.

I have a question though: does your roof slope? you don't want a situation where water is trapped under the 2x4s.

mccloud
Re: protecting asphalt roof

Based on the damage I've seen on the present roof, my guess is that the 2x4's would cut thru 2 layers of shingles in 10 years. I am considering putting metal plates under the 2x4s to distribute the weight, but am guessing they should be 4 or 5 inches wide to do any good. Yes, this roof does have a slight slope, something like 4" over 12'...that's the best I could do without having the deck higher than the patio door.

dj1
Re: protecting asphalt roof

In that case put 4 layers of shingles and you're good for 20 years. Inspect in 20 years and replace if needed. This is your cheapest fix.

Metal will cut through the roof even faster.

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