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Rafter Ventilation

Zogman

Well-known member
Joined
Feb 15, 2009
Messages
134
Location
So. Cal
My framers are almost done with my garage and it's time to move forward with siding and roofing which I will be doing myself. In planning for the soffits, I've been doing homework on the venting requirements for my garage. The garage will have vaulted ceilings with enclosed 2 x 10 rafters which will be insulated. The garage will have hardie backed siding and concrete shingle roofing. I've reached out to my inspector once and I really don't want to sound like a knucklehead to him with continuous questions so I'm reaching out to y'all to help me go into the right direction.

My initial question to the county was how much rafter venting I need and his response was "bottom 1/3 of the roof, as well as ventilation on the top 1/3 of the roof"

I'm having a hard time understanding that. In looking at houses with soffit vents, I notice that vents are placed randomly like every 6-10 feet apart. How the heck does venting get to each rafter when the rafters and the blocks are solid? Are people drilling vent holes in each rafter tail in the soffit area and drilling holes in each of the blocks?

I am seeing that LP Smartside makes continuous vented soffit panels and that looks like it makes sense. Does that mean I still need to drill holes in each of the blocks to allow air to get up into the rafters? Do I put baffles all the way up to the ridge or only 30% of the way up and down since the county said I need 1/3rd vented at the top and bottom. I'm just confused as heck and want to do this correctly.

I will have a ridge vents at the peaks.

Do I need to have venting for each of the dormers too??

I'm doing this myself and don't want to miss anything. Sorry if I sound like knucklehead. Your input is appreciated.

Zoli
 

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Chuck

Active member
Joined
Aug 30, 2005
Messages
42
Location
Smithfield, VA
Don't worry, in most localities the building inspectors don't understand venting for a cathedral ceiling either. :thumbup: Most are just trying to follow slightly out of date cookbook codes, most of which haven't worked well for cathedral ceilings built the last twenty years anyway. The codes are under revision right now, but it will be a while (years) before minimum ventilation rules that actually work make it to the localities.

Rather than trying to type it out, since it's not quite my main expertise anyway, let me point out this really good article from a guy who fixes problem cathedral ceilings, among other things. He knows a lot more about it than I do, and that article answered a problem I had with a much bigger commercial building a while back, too.

In my experience, after reading that article, you'll probably already know more than your inspector on the topic. :evil:
 
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