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Discussion Starter · #1 ·
I have a deck with a garage underneath and I want to insulate the garage ceiling. The 2x10 joists go perpendicular to the side of the house. I am rebuilding the deck floor right now and I need to know how this should be ventilated and insulated? The joists are level right now but I plan to give a 1/4" per foot slope to them so the deck will drain water.

Here is a picture of the garage ceiling.
 

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Discussion Starter · #3 ·
Dale I am in Vancouver Canada and the temperature goes from freezing to very hot and alot of rain.

#1.If I have a 4" space between the insulation and deck underside and also ventilate the ends would that do it?

#2. I need to get a slope to the deck surface so a friend said to lay the 2x4s perpendicular to joists to get a cross flow ventilation then lay the plywood over that. I think this is similar to your idea of the ceiling/drywall?

I plan on getting a really good garage door to keep heat in, can I use a vapor barrier in any of my two choices above for the ceiling?
 

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Discussion Starter · #5 · (Edited)
Thanks Dale,
Just to confirm before I start,
So if I ventilate each end every 16" that will do it eh? should I use a 6"x6" vent grate or 4"x4"?. The joists span 12' out from the house.

Would it be OK to cross strap the ceiling with 1x4's insulate then put a vapor barrier and drywall?
 

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Discussion Starter · #7 ·
Here is a pic of the side. The joists are perpendicular to the house so the side is the only overhang available to vent.

Right now it does'nt overhang over the wall. What is the importance of having a soffit as opposed to just having a vent on the end for every joist bay?



 

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Discussion Starter · #9 ·
thanks Dale, I will be using a fiberglass surface and I have already removed those wood railings since it would be a weakness for leaks like you suggested. I will go with a railing that attach's to the rim joist.

I have to use 2x4s ripped from 3" down to nothing to get a slope for the new surface and I was going to go right over the surface that is there now. Are you saying now to remove the whole surface and cross strap the deck and I could incorporate the slope as I go.

since the side of the deck/house is never really visible I would rather go with just vents.


 

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Discussion Starter · #11 · (Edited)
Well I got the front rim joist done for the front and replaced a few rotten joists. Tomorrow I will be doing the side rim joist. I still have not decided if I will put build a soffit or just vent the facia since the side of the deck will not be seen by anyone.

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