# Useless Ridge Vent?



## itwerx2 (Apr 3, 2007)

We had a continuous ridge vent installed when we replaced our old roof. Did not have one before.

When I went into the attic to see how it looked from the inside, I could not see the vent. And when I turned out the light in the attic it is pitch black- no light coming in anywhere at the ridge. 

Here is a picture inside the attic looking up at the ridge and towards one side of the house.. The three boards together (darker looking wood) form a beam all the way across the ridge from side to side.

Sure seems like a ridge vent is wrong for our type of construction since the beam inside seals off the ridge. 

Opinions appreciated.


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## AtlanticWBConst. (May 12, 2006)

itwerx2 said:


> We had a continuous ridge vent installed when we replaced our old roof. Did not have one before.
> 
> When I went into the attic to see how it looked from the inside, I could not see the vent. And when I turned out the light in the attic it is pitch black- no light coming in anywhere at the ridge.
> 
> ...


 
Not saying this is def. the case (tho, it looks like it)......

..... but, did they...possibly......attach the ridge vent...without cutting out the actual ridge sheathing....????


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## Ed the Roofer (Jan 27, 2007)

When you have a wide ridge beam or multiple ridge boards, the specifications require the slot cut out to be slightly larger than typical. I can not tell from your photo, because it is on an angle, but it does not appear to have the slot cut out past the ridge boards.

It should be, but I defer to the ridge vent manufacturers exact specifications first. They may not allow a slot so wide as your situation.

Ed


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## itwerx2 (Apr 3, 2007)

Ed- no, the slot does not extend beyond the ridge boards. No space between the boards and sheathing. 

Atlantic WB- as far as I know, the sheathing was cut. Would have thought the crew would have stopped the installation when they saw the boards there. But I've heard that finding this situation is not that rare and the crew usually just goes ahead.


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## AtlanticWBConst. (May 12, 2006)

Ed the Roofer said:


> When you have a wide ridge beam or multiple ridge boards, the specifications require the slot cut out to be slightly larger than typical. I can not tell from your photo, because it is on an angle, but it does not appear to have the slot cut out past the ridge boards.
> It should be, but I defer to the ridge vent manufacturers exact specifications first. They may not allow a slot so wide as your situation.
> Ed


Ed,...yes...that could very well be the case...:yes: ..

..that is a larger sized ridge beam....


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## itwerx2 (Apr 3, 2007)

So at this point it looks like we will be getting rid of the ridge vent and adding some square vents on the roof. 

What is the best way to deal with the slot that was cut for the ridge vent? Should metal be put on to form a new ridge before the cap shingles? Other recommendations? Thanks.


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## Ed the Roofer (Jan 27, 2007)

You could piece it in with a same width of new plywood to fill in the gap. One sheet at 3" wide will get you 128 lineal feet.

You can also have the contractor come back out and do his ridge vent correctly.

Get the specifications from the manufacturer of that particular brand of ridge vent from their website.

Ed


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## the roofing god (Aug 2, 2007)

usually we would shim the sheathing slightly higher on the beam so the air flow would reach the ridge vent


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## Ed the Roofer (Jan 27, 2007)

Good advice TRG, but a little out dated.

See the date on the OP.

It still may help somebody else though.

Ed


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## the roofing god (Aug 2, 2007)

since I saw you guys didn`t have a solution, I threw it out there,figuring someone else will run into it again:wink:


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## Ed the Roofer (Jan 27, 2007)

Besides your *alternative* and very costly solution, the better one would have, at that time, have the contractor come back out and cut the slot to the proper width as per the alternative dimensions provided by the manufacturer, when encountering a ridge beam, which was already suggested.

Ed


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## the roofing god (Aug 2, 2007)

no silly,he should have had the contractor come out ,remove the r.v.,shim up the plywood and reinstall it,the cut would be too wide for the ridge vent to sit right,and to have enough lap as water protection


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## tinner666 (Mar 14, 2005)

See it often and I think it was Shingle Monkey had one of his guys make the same mistake: The bevel wasn't set on the saw so the cut would be perpendicular to the ground! Just setting the bevel 45~ will give 3/4" more airflow.:thumbsup:


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## the roofing god (Aug 2, 2007)

it was a triple wide beam frank


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## Ed the Roofer (Jan 27, 2007)

I thought it was a double until your post # 12 when I looked closer at it, so I decided to shutup.

Ed


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## the roofing god (Aug 2, 2007)

NEVER question TRG,unless I`m wrong of course(perish the thought):no:lol


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## tinner666 (Mar 14, 2005)

Musta been 1/2 asleep. Missed the width post.


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## Ed the Roofer (Jan 27, 2007)

*Without knowing which brand of Ridge Vent is being discussed, I looked up the manufacturers specifications for the ridge vent slot opening, even when you come across a wide ridge board.

This method I previously suggested would certainly make more sense and be less costly than additionally having to remove or lift up the decking near the ridge and the shingles already attached to the decking, just to place shims under it.

TRG, you had me doubting myself for a little while, but I should have known better and stuck to my guns sooner. 

By the way, how thich of a shim would you feel is necessary to elevate the decking enough to achieve the rated 18" NFVA per lineal foot?

My thoughts would seem to indicate shimming the deckin up by 3/4" per side to perform similarly to a total of 1 1/2" wide slot cut on truss construction.

Ed





Air Vent’s ridge vent installation instructions
require the following when cutting the
ridge slot.​Slot Width:​**— If it’s ridge board or ridge pole*
*construction, *​*cut 3⁄4" **on each side*
*of the pole or board*
— If it’s truss construction, cut a​
*1​​1⁄2" opening​
Slot Length​*— Cut the slot length along the ridgeline​*6"​*​​from the end wall or hip intersection
— Cut the slot *12" *from a chimney or an
intersecting ridgeline​
*Cutting the Slot Wider​*Here’s a common question we receive about
slot width:​​*Can I cut the slot wider to increase
the Net Free Area?*​*
*Cutting the slot wider
will not increase the
Net Free Area because
the NFA will be restricted
to the openings on the
ridge vent.
For example, ShingleVent II is specified at
18 square inches of NFA per linear foot.
If you cut the slot 2" wide (instead of the
required 1​​1⁄2") it may seem logical that the
NFA would increase to 24 square inches
per linear foot. However, keep in mind that
the air that passes through the wider slot
must now pass through the openings in the
ridge vent itself. Although the slot is wider,
the ridge vent’s openings remain the same.
There’s no benefit to cutting a wider slot.​
*A word of caution:​*_​_​​There is the potential
for weather infiltration if the slot is cut​
*too wide. The vent needs to fully cover
the slot to protect the attic from weather
infiltration.​C A N Y O U
N A I L ¡ G U N
S H I N G L E V E N T​*​​​® *I I ?*​*
*the Ridge Vent Slot​*Cutting​*W I D E R I S N O T B E T T E R​*T I P :​*_​_​​​The slot width is designed to match the amount of Net
Free Area provided by the ridge vent itself. For example,
ShingleVent II has openings that total 18 square inches
of NFA per linear foot. Over the span of 1 foot, a 11⁄2" slot
width equals 18 square inches.
Likewise, a 3⁄4" slot on both sides of the ridge board or pole​
also equals 18 square inches over the span of 1 foot.


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## the roofing god (Aug 2, 2007)

seems like you just bolstered my point,I would shim it up a 1/2",so the air would reach the normal cut out,I don`t see where it says to cut it past a 4 1/2"beam to 5 1/2-6",what I see is
*
A word of caution:​*There is the potential
for weather infiltration if the slot is cut​
* 
too wide. The vent needs to fully cover
the slot to protect the attic from weather
infiltration. ( which is one point I made)the Ridge Vent Slot​Cutting​W I D E R I S N O T B E T T E R​T I P :​The slot width is designed to match the amount of Net
Free Area provided by the ridge vent itself. For example,
ShingleVent II has openings that total 18 square inches
of NFA per linear foot. Over the span of 1 foot, a 11⁄2" slot
width equals 18 square inches.
Likewise, a 3⁄4" slot on both sides of the ridge board or pole​
also equals 18 square inches over the span of 1 foot.(which was the other )​*


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## the roofing god (Aug 2, 2007)

so anyway thanks for cutting +pasting to prove what I was saying:yes: :laughing:


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## Ed the Roofer (Jan 27, 2007)

There was more in the document, which stated that you would need to add a bead of tri-polymer sealant under the ridge vent.

It does not specify widths of ridge beams, just how far to cut past them when they are in place.

On the roof common sense should dictate if youy have to cut too far.

The width of the SV II is 14" across including the external baffle, yet they still specify the slot to be cut the same for the SV II-9 and SV II-7, don't they?

_Whoops, I better go look that up, before I stick my foot in my mouth._

I sure hope that nobody heard that last comment. *Shhhh!*

Ed


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## the roofing god (Aug 2, 2007)

remember the cap is only 12",I know about using the sealant:laughing:


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## Ed the Roofer (Jan 27, 2007)

I correct myself.

The width is only 13 3/4" wide including the external baffles.

Ed


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