We are repairing a rear sun deck that is constructed of 2″x12″ douglas fir joist and 1″x8″ fir planking. Considerable termite infestation and dryrot has damaged a portion of the deck structure and plank sheathing. We plan to remove all damaged wood and replace in kind, with the exception of the 1″x8″ plank roof sheathing. Our question is: should we cut and remove the damaged 1″x8″ plank sheathing and replace with 3/4″ acx plywood and then overlay the entire roof deck with 1/2″ 5 ply acx in preparation for a granular bitumen (brae) roof system, or should we remove all 1″x8″ plank sheathing and replace with 3/4″x 4’x8′ T and G plywood (also used for subflooring)? One final note, the rear sun deck is also the roof for the rear portion of a single story garage.
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Please be more clear.
You call this a deck and refer to it in terms of it being a roof.
Just what is it that you have and what do you want it to be?
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First, thanks for replying to my question.
The structure in question is an existing one. It was built in the 40s to extend the garage into the rear yard and serve as a tool/work shop at the rear of the garage. The total area is 12'x12' with a concrete floor/slab and wood framed stucco walls on three sides. It's lid or cap is a sloping wood floor which serves a dual purpose: 1. it a roof over the tool/work shop and 2. a sun deck off of the rear second story bedroom. At present, a number of the 1"x8" sheating planks need replacing. We are leaning toward removing all the old 1"x 8" planks and replacing them with 3/4" T and G subflooring. A new roof will then be installed over the new ply subflooring. We are aware that a pressured treated subflooring material is available and am wondering if this would be a wise investment for this repair?
I still can't get my mind around the fact that all you have on this is 1x8 fir and no roofing material. No wonder it is rotting! what has been keeping the water fromn running into the garage?It sounds like you now want to both repair the rot and add roofing material. that is gfood for the fgarage, buit not all that comfortable to use aas a sun deck. If you want both a water tight roof and a wood sun deck, there is a lot more involved.anyway, you need to remove rotted material. To have a good base for roofing, you should use plywood first. I'll wait for clarification of your goals before going further
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I apologize for the unclearness of what we are repairing. Let me restate what we are attempting to do:
Imagine a flat roof with a slight slope to carry water to a scupper that serves to keep water out of the garage and a roof/deck that can be walked and sit on. We are replacing the damaged roof deck substrate which was originially built with 2"x12" joists and 1"x8"s for sheathing. The damaged joists have been replaced with new material and we now want to resheet the roof/deck with P.T. T and G subflooring. Lastly, the roof/deck will be reroofed using a roof system designed for flat roofs that can also serve as a deck.
I hope this makes our project a bit clearer.
thanks,
John
No problem.
It is fairly common for people to only partially describe what they have, because they can see it and assume we can too, but when it is a non-typical situation, it is harder to imagine from this end. The more common method is to have the roofing membrane of=ver the sheathing like yours, then sleepers and a wood deck for the walking surface which prevents damage and wear to the roof and is more comfortable under foot.But if you have a membrane roof product chosen that can handle the traffic and you are happy with that, I would proceed as follows,Replace all the rotted 1x8 first.
Then skin the whole surface with an exterior grade sheathing. It does not have to be 3/4" since you have strength already. 7/16" Advantech or 15/32plywood will do. The goal is to give a smooth surface under the roofing materials. The 1x8 would flex between boards and stress the roofing. With the smooth solid surface, you are ready to go with your roofing.
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What was the original roofing material? There had to be one, he's got stucco walls.If you didn't have time to do it right the first time, how come you've got time to do it over again?
He's a little unclear about that. Sounds like a selvedge split sheet rolled in bitumen. New is probably something like Polyglas
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
The approach I took...
http://forums.taunton.com/tp-breaktime/messages?msg=91581.1