Ridge Vent over Ridge Beam

[Samh]

So the short of it is, was originally planning on doing gable fan and having an active system, but after reading the thread about passive being better, because it can't break had me thinking about switching. The catch? I framed the rafter to sit flush with the ridge beam, instead of up an inch.

Looking for options.

Option 1
I have heard about notching the top of the ridge beam, which would require a call to the LVL manufacturer to see if that is acceptable. This would be the easiest, and least costly.

Option 2
Having a wider than normal ridge vent, roughly 5" wide cut at the top. Worry about leaks, as that isn't per ridge manufacturer recommendations. This would be easy, but risk of leaks

Option 3
Install spaced boards on the rafters, then sheathing on top of that per this
https://www.mynevadacounty.com/DocumentCenter/View/15438/Roof-Nailing-Over-Skip-Sheathing-PDF
This would be more costly, but would make sheathing a little easier.

 

[Stuart in MN]

You don't have to use a ridge vent, regular roof vents work as well.

 

[kbs2244]

If you have open space under the rafter bottoms, do as Stuart suggests
It is too late for a ridge vent.

 

[rerod]

I would go back to your gable vent plan, and have two large ones each side. I read a article recently talking about how passive doesn't work as well as we hoped. Especially with lower pitched roofs like four and five twelve.

I had some custom gable vents built for my dads place, like 6' wide, and they really worked well.

And I don't buy the short circuit theory when placing additional vents close to the gable vent. The more the better.

 

[Commendatore]

And I don't buy the short circuit theory when placing additional vents close to the gable vent. The more the better.

Pesky science, what does it know!

 

[matt_i]

So do you have a double thickness (3-1/2") LVL ridge beam? As I framed a single (1-3/4") ridge LVL with flush rafters and it worked fine with GAF Cobra ridge vents. I used 1" wide air-gap at the top of the sheathing.

I wouldn't notch the LVL, that's a recipe for problems.

What stage of framing are you in? Is it possible to taper the top piece of sheathing up by 3/4" or 1" by using stepped spacers? This is where a tablesaw would come in handy as you could rip 2x material into a set of say 16" tapers, 0 to 1/4, 1/4-1/2, 1/2-3/4 or the like. I'd simply glue that down with construction adhesive and then nail thru it all using #10s. You can calculate the 3/4" x 22-1/2" area vs the soffit area and see if thre's a restriction at the top. That should give roughly 8.5 sq-in per linear ft.

 

[noslin]

using a rigid vent such as the cobra or lomanco lor9-4, cut your vent wherever you want close to the ridge, cut vent in half, install over vent then have your roofer fab you up a steel ridge and screw through it and the vent into the deck. you can fab whatever width steel ridge cap like would be used on a metal roof.

further, either only have ridge vent, static vents, or gables, not any combo if them. if you have static and gable vents then where is the intake really coming from? the eave?.. doubt it. the air doesn't know whats in/out at that point. if you use static vents then put them all on one side of the ridge, dont split between sides or again, the air gets confused as to what is in/out.

dean

 

[captaindiode]

See this detail from The Journal of Light Construction (JLC)

https://www.jlconline.com/how-to/roofing/q-a-wide-ridge-vent_o

 

[rerod]

See this detail from The Journal of Light Construction (JLC)

https://www.jlconline.com/how-to/roofing/q-a-wide-ridge-vent_o

I like that custom made ridge vent. Even if you didn't have the ridge beam in the way, how can rolled ridge vent even perform? Even the good shingle vent II used on my house barely breaths imo..

I'm all about venting your roof. Id like to incorporate the houston cool roof theory on my new home. But its like building a second deck and may not be cost effective.

 

[Falcon67]

I have five 9" passive vents along a 40' run, venting seems to work very well. Same with the house roof - too many hips and short ridges to make much use of ridge venting.

 

[Samh]

So do you have a double thickness (3-1/2") LVL ridge beam? As I framed a single (1-3/4") ridge LVL with flush rafters and it worked fine with GAF Cobra ridge vents. I used 1" wide air-gap at the top of the sheathing.

I wouldn't notch the LVL, that's a recipe for problems.

What stage of framing are you in? Is it possible to taper the top piece of sheathing up by 3/4" or 1" by using stepped spacers? This is where a tablesaw would come in handy as you could rip 2x material into a set of say 16" tapers, 0 to 1/4, 1/4-1/2, 1/2-3/4 or the like. I'd simply glue that down with construction adhesive and then nail thru it all using #10s. You can calculate the 3/4" x 22-1/2" area vs the soffit area and see if thre's a restriction at the top. That should give roughly 8.5 sq-in per linear ft.

Yes, doubled 1-3/4" LVL for 3-1/2" total. If I am reading this correct, you are saying make a tapered shim for the top of the rafter to give the space between the plywood and rafter? That sounds like it could work.

 

[matt_i]

Yes, doubled 1-3/4" LVL for 3-1/2" total. If I am reading this correct, you are saying make a tapered shim for the top of the rafter to give the space between the plywood and rafter? That sounds like it could work.

Exactly. The last 48" of length, measured along the rafter top surface, is where you'll taper up from 0" to 3/4" or 1" to emulate the gap that would be created if you had started with the rafter raised. Its going to require some production work with a tablesaw but apart from setting up the jig and ripping pieces for an hour or two, then installing them, its just work and nothing highly complex. I don't think a 3/4" rise in the pitch over 48" is going to be very noticeable, shingles will surely not care.

 

[Samh]

I like that custom made ridge vent. Even if you didn't have the ridge beam in the way, how can rolled ridge vent even perform? Even the good shingle vent II used on my house barely breaths imo..

I'm all about venting your roof. Id like to incorporate the houston cool roof theory on my new home. But its like building a second deck and may not be cost effective.

If I read that article correctly, I should just sheath the roof normally, with no cut for ridge vent at the top, then do an Above Sheathing Ventilation or Above Sheathing Radiant barrier. That might be the best way to go.

 

[Bretny]

I have a ridge vent. Didnt work, had mold in my attic. Now i have gabel vents and an attic fan.