Dealing with overly wide ridge vent slot?


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Old 09-28-22, 04:46 PM
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Dealing with overly wide ridge vent slot?

Folks - For the ridge vent replacement project from my previous thread, it turns out that the slot already there is just shy of 4 inches wide. There is a ridge beam, which is made up of two sistered boards - looks like 1x4s.

The GAF Cobra Snow Country vent instructions specify a maximum slot opening of 3 1/4". Is that max from air flow considerations, or from the needs of the fit and nail placement of the vent itself?

And, how would you go about narrowing the slot? I can certainly rip some narrow strips of sheathing, nail them in , then add some felt and shingles to bring the roofing material up to the edge of the new, narrower slot. But it's a bit of work to do that, so if it's not needed or there's a better solution, I'd love to hear.

Many thanks for the assist.

Ken Platt in Granby, CT
 
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Old 09-28-22, 05:38 PM
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So a 4" wide opening with a center ridge board of approx. 3"?

It's the total opening, width x length so adjust as necessary.

It's a guideline as some regions state a ratio of 1 sq ft of opening per 150 sq ft up to 1 sq ft of opening per 300 sq ft.
Personally, if your in the ballpark I would not go to extremes.

BTW, that is the produce I used on my garage project this summer, have it on my other shed as well!


 
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Old 09-28-22, 06:07 PM
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Marq1, the total opening is 4 inches with about a 1.5" thickness/width ridge board. I am not sure if that makes it "in the ballpark" or not. Do you know, is it an issue with the air flow (which I'm not that worried about) or that the bigger gap might cause nails to miss the decking or allow water infiltration?

Also, if I could ask you as a user of this product, it's not clear to me from what I can read how the ends are closed off? (I've not yet actually held the vent, so this might be a dumb question)

Any tips, or things you wish you'd known the first time around?

Much appreciated -

Ken
 
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Old 09-28-22, 06:19 PM
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I don't know that I'd worry too much about an extra 3/8" on each side. But if you want to follow their instructions to the letter, I'd probably just put a strip of #30 felt down and make the gap between the felt on each side 3 1/4" apart.

As for end caps... their instructions say: "Be sure the finished end is installed to the outside to prevent weather infiltration." Apparently that is all they feel is needed.
 
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Old 09-28-22, 06:26 PM
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Xsleeper, do you mean you'd just have the felt hanging off the edge of the slot, kind of sticking out in the air?
 
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Old 09-28-22, 06:49 PM
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Yes, 3/8" above the cut in your sheathing.
 
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Old 09-28-22, 07:26 PM
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Thanks.
 
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Old 09-28-22, 11:58 PM
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what I can read how the ends are closed off?
Ends have the filler (foam) material so the ridge shingles on the roof, assuming the opening is not continuous end to end, butt up to the end of the vent, then the ridge shingles go on top.
 
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Old 09-29-22, 06:50 PM
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Thanks. Trip to Home Depot to buy stuff tomorrow.
Ken
 
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Old 09-29-22, 08:33 PM
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The ambiguity is probably due to whether or not you use the sticks (preformed lengths) or the roll (which gets field cut to length.) So depending on which you buy, the answer may vary.
 
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Old 09-29-22, 09:36 PM
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Hi Ken, keep in mind that ALL calculations for air flow, NFA, et al are more or less a wild guess. Far too many variables to include them all so they settle on a "good guess". Make sure your nails have something to hit but as for airflow plenty close.

Bud
 
 

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