# Are Ridge Vents only supposed to be cut on one side?



## Windows on Wash (Aug 30, 2011)

The air is still moving in this case regardless of the side that is cut. Its supposed to be cut on both sides though.


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## Bud9051 (Nov 11, 2015)

Instructions usually call for being opened on both sides. Have they installed the actual ridge vent yet?

I'm sure he will have an excuse but you want to see the mfgs instructions and make him follow them. We can review the required amount of ventilation you should be looking for.

Add your nearest big city to your profile so we will have an idea as to your climate abd building methods.

Bud


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## BayouRunner (Feb 5, 2016)

I agree suppose to be cut both sides. Is that felt we are looking at or the ridge vent? I’m not a roofer but have been in hundreds of attics. I’ve never seen one cut on just one side


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## pindude80 (Oct 28, 2018)

Windows on Wash said:


> The air is still moving in this case regardless of the side that is cut. Its supposed to be cut on both sides though.


Ok, my question is if only one side is cut is enough air moving? I kind of had a feeling it was supposed to be cut on both sides.


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## pindude80 (Oct 28, 2018)

Bud9051 said:


> Instructions usually call for being opened on both sides. Have they installed the actual ridge vent yet?
> 
> I'm sure he will have an excuse but you want to see the mfgs instructions and make him follow them. We can review the required amount of ventilation you should be looking for.
> 
> ...


Bud, thanks for the reply. 

Yes, they have installed the ridge vent, shingled over it and are done with the job.

They supplied the vent so I'm not sure what brand or what the manufacturer's instructions say.

I live in Cincinnati, OH


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## pindude80 (Oct 28, 2018)

BayouRunner said:


> I agree suppose to be cut both sides. Is that felt we are looking at or the ridge vent? I’m not a roofer but have been in hundreds of attics. I’ve never seen one cut on just one side


The black that you see is the underside of the ridge vent.


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## Nealtw (Jun 22, 2017)

pindude80 said:


> Ok, my question is if only one side is cut is enough air moving? I kind of had a feeling it was supposed to be cut on both sides.


They usually cut both sides, that does not look cut. They may have found a joint there with a small piece on top that they just removed and maybe that was bigger than they usually cut. It will work just fine.


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## DallasCowboys (Jan 30, 2017)

Maybe you could call the manufacturer of the ridge vent and see what they recommend.


Or call the Building Inspectors.


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## Bud9051 (Nov 11, 2015)

On a roof that has a ridge board as yours does the proper way is to cut the opening one inch to each side of that center board. *Here's* a link with an illustration. 

If he has some reason for the half (A$$) job we need to hear it, but I can't think of any that would follow any ridge mfgs guideline. Basically he has provided half the high NFA (net free area) for the suggested ventilation. Will that be enough?? We can only guess at this point but you are in a cold climate (OH) so venting unwanted moisture is important.

It will be easier for him to drag his feet and hope you go away. If you haven't paid in full you could use that money to motivate his, but removing what is there and re-installing it would be a poor job. The existing vent should be replaced with new and all of the extra holes created should be sealed.

He has provided half the vent capacity of that ridge vent. How much you actually need has not been determined and we can help.

Bud


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## pindude80 (Oct 28, 2018)

Thanks for the link with install instructions. I will contact the contractor and see what he has to say. I would much prefer that it was cut on both sides. Good point about not just venting hot air but venting moist air in the cooler seasons.

I paid the last part of what I owed them when they finished up last week.

What do I / we need to do to determine how much ventilation I need?


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## pindude80 (Oct 28, 2018)

Nealtw said:


> They usually cut both sides, that does not look cut. They may have found a joint there with a small piece on top that they just removed and maybe that was bigger than they usually cut. It will work just fine.


It's definitely not cut on both sides. According to the instructions Bud linked me to there is a 1" minimum cut needed on both sides so maybe like you said they cut a wider gap but I'll have to get up there with a tape measure to check.


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## huesmann (Aug 18, 2011)

Definitely contact the installer. I bet the manufacturer has install specs that must be followed if you ever need to make a warranty claim. If the spec requires the vent to be cut on both sides, and it isn't, you may be SOL in a claim situation.


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## pindude80 (Oct 28, 2018)

Good point about if a claim would need to be made and my warranty, whatever it may be, would be void if it wasn't installed to their specs. I'll have to contact the contractor, find out what kind it was, either call or look up online what the install calls for.


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## Bud9051 (Nov 11, 2015)

Ventilation guidelines are dependent upon the age of the house and how well the ceiling to attic layer has been sealed, usually just normal which does not qualify as sealed. Older homes definitely not unless a major effort was undertaken to do such sealing.

Anyway the normal guidelines are 1 ft² of NFA (net free area) for every 150 ft² of attic floor. That number is then divided in half with half going high and half going low. Soffit vents and ridge vents are a common combination and each vent has a rated NFA.

If the house is newish and was specifically air sealed then you can use half of that number (1 ft² NFA for every 300 ft²). But you would likely be running a heat recovery ventilator in such a tight home.

Ridge vents are usually rated to provide 18 in² of NFA per linear foot, 9 on each side. A 40' ridge vent would provide 720 in² or 5 ft². Give us the size and age of your house and a description and we will factor those details in.

Bud


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## pindude80 (Oct 28, 2018)

My house was built in 1966, it's a 1360 square foot ranch. I don't know anymore specs than that off the top of my head. Do you need any other information?


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## chiraldude (Nov 16, 2013)

I would tend to agree that there will be plenty of air flow around that beam. As long as the soffit and ridge vent total area meet the spec, there won't be any moisture accumulation. 
That said, if it did come down to a warranty claim for whatever reason, the manufacturer would be certain to point out the unbalanced cut and use it as an excuse to deny the claim.


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## Nealtw (Jun 22, 2017)

Or maybe the roofer was concerned about the prevailing wind from one direction.


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## pindude80 (Oct 28, 2018)

I just took a measurement of the cut width.


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## pindude80 (Oct 28, 2018)

What kind of warranty claim would be possible, the vent itself being faulty or damage caused to the roof because of the vent?


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## Nealtw (Jun 22, 2017)

If the house is 40 ft long you have over 4 Sq Ft.


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## Bud9051 (Nov 11, 2015)

As I remember some ridge vents provide a ¾" gap on each side, thus 1.5" total opening to the air. Multiply that times 12" and you get their claimed 18 in² per linear foot (9 on each side).

With an attic floor area of 1360 you would need a total NFA of 9 ft², 4.5 ft² high and 4.5 ft² low. Some back of hand calculations with your 1.25" gap I came up at just over 4 ft² for high area. I hate cutting this guy any slack but from a technical point of view your high vent area will do just fine. Add to that any additional air sealing you do, which is always a top priority, will reduce the suggested NFA. Also, the suggested NFA is not a hard number in that 10% short and you will have a disaster. As long as you have low vents half of what you ended up with would work.

Bud


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## pindude80 (Oct 28, 2018)

Bud9051 said:


> . Also, the suggested NFA is not a hard number in that 10% short and you will have a disaster. As long as you have low vents half of what you ended up with would work.


What are low vents, sofitts?


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## Bud9051 (Nov 11, 2015)

Soffit venting is probably the most common and traditional ranch from 1966. However, back then they weren't a generous with how much venting they installed, often a few smaller vents along each overhang. That in turn often gets covered with vented soffit panels without enlarging the openings they covered. You should do some checking to see what you have Baffles on the inside in each rafter bay as well. And as always, pictures.

Bud


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## 3onthetree (Dec 7, 2018)

Bud9051 said:


> Ventilation guidelines are dependent upon the age of the house and how well the ceiling to attic layer has been sealed, usually just normal which does not qualify as sealed. Older homes definitely not unless a major effort was undertaken to do such sealing.
> 
> Anyway the normal guidelines are 1 ft² of NFA (net free area) for every 150 ft² of attic floor. That number is then divided in half with half going high and half going low.
> 
> If the house is newish and was specifically air sealed then you can use half of that number (1 ft² NFA for every 300 ft²).


Which "guidelines" are you pulling this from?


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## pindude80 (Oct 28, 2018)

I am going to call the contractor. I know I would definitely feel better if both sides of the ridge were cut. I am going to bring up the warranty thing. What type of warranty problem would we have, with shingles or with the vent?


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## BayouRunner (Feb 5, 2016)

Duplicate post


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## BayouRunner (Feb 5, 2016)

I think your approach might be better with your contractor to tell him the wood is supposed to be cut on both sides. And that you want it done proper. If you tell him you will feel better if it would be cut then you might have some issues. It’s going to cost him a few dollars but not too bad. He can reuse the vents but will probably have to change the shingles on the cap itself. Hope it works out for you. A good contractor won’t blink an eye about that. Most likely someone on the job is going to get some slack, rightfully so. Having any documentation from the manufacturer liked mentioned in a previous post would be good to have.


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## pindude80 (Oct 28, 2018)

BayouRunner said:


> I think your approach might be better with your contractor to tell him the wood is supposed to be cut on both sides. And that you want it done proper. If you tell him you will feel better if it would be cut then you might have some issues. It’s going to cost him a few dollars but not too bad. He can reuse the vents but will probably have to change the shingles on the cap itself. Hope it works out for you. A good contractor won’t blink an eye about that. Most likely someone on the job is going to get some slack, rightfully so. Having any documentation from the manufacturer liked mentioned in a previous post would be good to have.


Yeah, I'm going to tell him I did some research and everything I see says that it's supposed to be cut 1" minimum on both sides. I also want to bring up the warranty thing and then get into asking what the instructions say and if they didn't follow the instructions the manufacturer will deny a warranty claim.

Can he reuse the vents? I thought someone earlier in the thread said that they couldn't reuse and have to buy new. It's probably ok, but they didn't install a ridge vent on top of my garage and I was thinking maybe that is because it shares the same attic as the rest of the house?


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## Bud9051 (Nov 11, 2015)

3onthetree said:


> Which "guidelines" are you pulling this from?


There are many sources and the definition changes a bit from author to author. This *link* touches on both the 1/300 and 1/150 rules but their reason stated isn't exactly complete (IMO).

The need for a vapor barrier has been replaced by good air sealing and many modern homes are addressing that issue at the time of construction. With an existing home retrofitting a good air sealing job is difficult so ventilation area should lean towards the 1/150 guidelines.

Keep in mind that ALL referenced, even codes, pointing at either 1/150 or 1/300 are NOT exact requirements. Anything close counts in ventilation.

Bud


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## ChuckTin (Nov 17, 2014)

Wife and I put together a "kit" shed on a slab in our back yard. All the raw pieces plus instructions. When we got to the roofing I wanted a ridge vent and left the decking (chipboard) shy of the roof. Mind you we're talking small here, 10x12 floor if memory serves. And while I don't recall measuring the gap I'm certain it was more than 1.5" each side of the ridge, probably closer to 2".
With the roofing in place but the ridge gap uncovered the solar gain pumped an obviously noticeable breeze out of the ridge. Then I installed the ridge cap and that blocked almost all (90%?) of the venting. This was Spring in the early 90s and the location was East Central Florida and less than 10 miles inland.
In your case, and a full size house, I'd be concerned about the mechanical anchorage of the roof decking and the size/location of the soffit vents - to have air flow out the ridge you must need a fluid source which is what soffit vents provide.
You picture suggests to me that that is the ceiling of the attic envelope and not the bottom of the roof decking. If so it's interesting that the interior is still vented to the underside of the roof decking. But without more details deciding whether the contractor did an adequate install is iffy at best.


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## 3onthetree (Dec 7, 2018)

Bud9051 said:


> There are many sources and the definition changes a bit from author to author.
> 
> Keep in mind that ALL referenced, even codes, pointing at either 1/150 or 1/300 are NOT exact requirements. Anything close counts in ventilation.


Attic ventilation is specifically referenced in building code, going back to even BOCA. The direction you give has the general gist of it and isn't really wrong, but since this comes up so often on this forum, it probably should be stated exactly just like advice does with electrical and plumbing. Codes are exact, but can be a minimum starting point.


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## Bud9051 (Nov 11, 2015)

Unfortunately quoting any code specifying 1/300 or 1/150 would not be exactly what is needed, other than what a building inspector might think is needed. This is a case of a wild guess being passed around until everyone forgot it was a guess from the start so it became the code. Fortunately Bill Rose did some digging and provided us with some *history* on this ventilation requirement and why we need to consider it as a "general" starting point and not an absolute number. I have read here on the forum where posters have taken these calculations to be a must or failure is certain.

We can review some of the variables but one example is NFA. It is an imperfect number even when we can find it stated by the manufacturer. When not listed somewhere we must guess at a number typical of that style vent. In effect we end up using a guess for calculating an exact number, not good and not something that should result in failing an inspection.

Writing building codes is not easy and building inspectors don't like complex requirements so they get 1/150 or 1/300 as their only choice and despite the vagueness the masses end up following it. 

Bud


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## finisher65 (Apr 7, 2019)

I'm not a full time roofer although I've done quite a few. Having read the whole thread I agree with Buds take on this


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## craig11152 (Jun 20, 2015)

My gut instinct is the guy cut one side to save time....8 minutes? 
While the ridge vent may function OK I'd be lying awake at night wondering what other shortcuts he took.


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## Bud9051 (Nov 11, 2015)

@ craig, a different part of the house, siding, but an example of what some contractors will hide. When I removed the old hardboard siding after 30+ years I uncovered to original felt paper used over the plywood. To one side of my front door, standard cape, and between the two windows he had apparently run out of felt. No problem, he just collected all of the scraps and patchwork style covered that 1/4 of the front of the house. Some pieces were 4" by 16" with no attempt to overlap to direct any water down to the bottom. He just wanted it all to look black and quickly covered it all with siding.

When they know they will be long gone before anyone will discover their short cut they may do anything that puts money in their pocket.

Bud


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## craig11152 (Jun 20, 2015)

The worst thing I ever saw was a 4/12 pitch 2 story house, your basic rectangles and homeowner had called because a leak developed in a back bedroom.When I climbed up on the 2nd story and went to the back I could see large swathes of shingles, sealed together, but lifted and folded so large amounts of felt paper were exposed. Somebody had roofed it using hand staplers with T50 1/2 inch staples. I folded back what I could, tossed some roofing nails in to hopefully hold them down short term and gave the homeowner the bad news. 
We ended up getting the job to replace the roof and tore it off by hand in 10 minutes.


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## AllanJ (Nov 24, 2007)

Who signs off on the warranty to put that into effect?


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## RAYDOG59 (Feb 4, 2020)

Hello, is it possible that you have a lower pitch on one side, for instance i have a 2/12 pitch on back side and 6/12 on front side im having same problem


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## pindude80 (Oct 28, 2018)

RAYDOG59 said:


> Hello, is it possible that you have a lower pitch on one side, for instance i have a 2/12 pitch on back side and 6/12 on front side im having same problem


Nope, the pitch is the same on both sides of the ridge.


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## P C D (Jan 24, 2020)

I would thank your roofer for leaving half of your roof diaphragm with its boundaries intact.


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## RAYDOG59 (Feb 4, 2020)

P C D said:


> I would thank your roofer for leaving half of your roof diaphragm with its boundaries intact.


 Hello, can you deliberate a little on this discussion with my post 

thanks


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## ChuckTin (Nov 17, 2014)

I think he's being sarcastic.


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## ChuckTin (Nov 17, 2014)

Only one time have I seen a ridge vent vent in a way that I thought was proper. We were building a small 12' x 12' tack room for a single pony. The roof was low slope and the plywood decking left about an 8" (4" on either side of center ridge) before we applied the roofing. Any slight breeze passing over the roof meant an _obvious_ breeze inside as the formed vacuum pulled air in thru the door and out the ridge gap. After we capped the ridge by covering it a short piece of ridge cap the venting was minimized.


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## P C D (Jan 24, 2020)

RAYDOG59 said:


> Hello, can you deliberate a little on this discussion with my post
> 
> thanks



The ridge board in your roof is one of the required boundary elements in any diaphragm. Your roofer only butchered half of it. In practice it should not worry you, because typical wood structures contain many structural redundancies.


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## P C D (Jan 24, 2020)

ChuckTin said:


> I think he's being sarcastic.


If that was in reference to my reply, I would appreciate it if you would refrain from any such commentary on my opinions in the future.


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## ChuckTin (Nov 17, 2014)

Oh dear.


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## BigJim (Sep 2, 2008)

P C D said:


> If that was in reference to my reply, I would appreciate it if you would refrain from any such commentary on my opinions in the future.


Little touchy there aren't you?


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## P C D (Jan 24, 2020)

BigJim said:


> Little touchy there aren't you?



I would appreciate it if you would refrain from offering commentary on my person in the future. That is not _nice_.


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## P C D (Jan 24, 2020)

bigjim said:


> little touchy there aren't you?



kiss my ass, bigjim.


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## BigJim (Sep 2, 2008)

P C D said:


> kiss my ass, bigjim.


That may be your thing but I am not wired that way. See ya, have a nice life on another forum.


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## Nealtw (Jun 22, 2017)

RAYDOG59 said:


> Hello, can you deliberate a little on this discussion with my post
> 
> thanks


 I have not heard anyone mention that, that is something to worry about. 

The sheeting structure holds the roof square as well as holding the house square. The ridge board is there to hold the rafters in place, with trusses the ridge board is just blocks between them . We do nail the top sheet to the ridge. Before we had plywood and OSB it was sheeted with individual boards.
I have not heard of any places that make it against code to have ridge vents. 

Usually they remove some on both sides. Maybe one side would be better if you have prevailing winds in one direction. It is always best to have more intake than exhaust and hot air can move very quickly when it wants to get out. PCD might be a good example of that. :vs_cool:


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