insulating garage roof w/ patio deck
Hi all,
This Fall I rebuilt a deck which is also the roof of part of the garage. All sorts of marvelous fun including but not limited to replacing the garage door header and all the joists, adding a cantilevered overhang and lots of brooding, hemming and hawing over deck surface/waterproof protection as a roof.
For better or worse I chose a Sonoguard system of basically a liquid self leveling urethane membrane over 2 layers of 3/4 plywood and which has a renewable UV protecting topcoat of more urethane over some rubber granules broadcast into the bottom coat for non skid. Looks kind of like a boat deck or a tennis court. All went basically as well as I could have hoped considering terrible weather and leaves trying to fall on it. The 2 layers of 3/4 was probably overkill, but I wanted it to be strong and not deflect at all under foot.
Now I’m trying to figure out the best way to insulate it and prevent condensation since snow and ice will be sitting on it. I figure it’s the same problem as a cathedral ceiling requiring an airspace and soffit vents? I am intending to treat the bottom of the overhang like a soffit with plywood and a vent or aluminum vented soffit material. Should I drill a hole in the blocking to the overhang in each bay near the top, leave say a 1 1/2 – 2″ airspace under the plywood, fill each bay with say a combination of rigid foam and fiberglass or say fiberglass in each bay and rigid foam across the whole surface as the garage ceiling as the previous owners had? The garage is heated as it is a workshop and because it is under the living room and keeps the floor warmer. It seems like there a more way to insulate things and allowing for adequate breathing for the materials isn’t always as simple as it seems. Or is it?
If anyone wants to know more about the Sonoguard system I’m happy enough to share my thoughts.
Thanks and hope this is enough info.
Cheers and stay safe (and warm and happy and employed!)
Bob
Replies
will all or part of this be sheetrocked?
I'm thinking best choice would be spray faom urethene insulation.
But if DIY, then staple up a vapour retarder membrane, blow in cellulose or chopped FG, and leave, or sheetrock over it. No venting.
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Thanks, wasn't planning on sheetrock as none of the rest of the garage ceiling is. Had considered t&g pine as that is cheap here in Maine and suits the general woodsy ambiance. Thought condensation would be a problem. If not venting would a person insulate the whole space so it is more like a sips panel w/ foam, like Tiger foam against the underside of the plywood and around all the joints in the blocking. No air space no condensation?
I guess I got this old school notion that everything has to be able to breathe? I have the same confusion about how to best insulate the box sill and rim joist. It is just FG now seems like foam would be better, and at least that doesn't get snow sitting on top of it.
Anyway, thanks Piffin.
Bob
I'm in Maine too.Choice of a spray foam includes the VB as part of it. the foam IS the VBWitha blown in, a vapour retarder instead of barrier will let moisture dry back out if it gets into the assembly.some concern about "as none of the rest of the garage ceiling is." because you really should have that fire barrier between garage and living space. there are lots of things in a garage that are fire sources. You also do not want the CO gas from exhaust getting to the living space.
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Thanks, all good points.
Your concern about the fire barrier between the garage and the living space is a good point, although the joist space and the ceiling is a labyrinth of pipes, wire, hot water heat tubes and fins. Also it is handy for access to reroute or add wiring. All excuses, but also the heat from the garage keeps the living room floor warmer. We have never parked in it as we have been working on the house ever since we moved in, but your point about CO gas from cars someday is still valid. Maybe I could drywall it.
We already have a seemingly never ending list of things that have to get done someday, with heat and insulating things as well as possible appearing the highest current need.
Sure does get dark early these days, especially on Sundays!
Bob
Sure was wet last night. Waves of water slapping the east side of my house in the wind.
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