[johnny67]

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.

 

[Dale Chomechko]

Fiberglass insulation would be fine but I don't think you will get much ventilation in there. It isn't living space so you may just omit the vapour barrier. Your overhead door will not help in retaining the heat anyway.
If you realy want to ventilate it you could remove the cross strap your joists with 1x4's or 2x 4's then sheet it.
Ventilate the ends -screen them- then put a metal drip over them about 1/4-1/2" away allowing air flow under them.
Might help if I knew what part of the contry you were in
Dale Chomechko
DC Roofing Inc

 

[johnny67]

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?

 

[Dale Chomechko]

That would do it
I live in Surrey so I understand the weather only too well.
We live in a rain forest, this is why I asked & it is important here to ventilate it.
The reason for cross stapping would be so the air could move in all directions, but given that you may not have the luxury of the extra height that it would give the deck, you could jusy ventilate the ends. But would have to do them all.
Look me up at dcroofing.ca
Dale Chomechko

 

[johnny67]

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?

 

[Dale Chomechko]

If the joists extend over the exterior wall, just insulate up to the wall & the overhang is your soffit, aluminum or vinyl soffits would work.
Just make sure there is an airspace above.
Is the overhang on both ends along the whole deck?
If so, then soffit venting would be enough.
Send an exterior pic if possible.
Dale

 

[johnny67]

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?

 

[Dale Chomechko]

A soffit looks cleaner

Take the plywood off
Add fascias
Cross strap it with 1x4 & resheet it with plywood
Install venting on both sides
If you extend the joists out another ft you could put soffit under that as well.

Option #2 might be a little more creative for your needs
Extend your 1x4 1/2" to 3/4" beyond the fascias
Extend your plywood 3/4 inch beyond that & install a 1x2 for your trim
Be sure to screen the inside for bugs.
This leave a watertight unseen gap on both ends

I am assuming you going with a vinyl deck & aluminum screwed into the deck(which I don't personaly like)
Wood posts notched out will work bolted through your fascia
The existing post & rail system is only asking for trouble in our climate

 

[johnny67]

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.

 

[Dale Chomechko]

Just thinking of water penetration through the vents into the wall. seal the vents well.
It's also a looks thing with me.
I do a lot of renos as well as finishing work & cabinet work.
I'm not a perfectionist but do concider how I see something & if it looks proffesional.
This is what will sell it in the future.
I like covered decks in our area as well, because it gives them an almost year round usability in our mild climate
Give me a call. My # is on the website, I'm always on the road, may come by & take a look.

Dale Chomechko
DC Roofing Inc

 

[johnny67]

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.

Before

After

 

[747]

You get a high five for the Ford pickup:laughing::thumbsup: Thats a clean little Ford pickup you have there.

 

[johnny67]

yeah it's a good truck, can take alot of weight in the box. I have it filled right now with concrete up to the top.