# Can you ridge vents 3:12? 2x15lb or 2x30lb



## MB1 (Dec 13, 2011)

I just had two different roofing companies bid my house for a new roof. One says they will not (and cannot anyways) put in ridge venting given a 3:12 roof. They say it is prone to leaking with wind driven rain. The other says they do it all the time and use the best system on the market called Shingle Vent 2. Which do you recommend?

Also, given that I am in San Jose, CA is it worthwhile going 2 x 30# felt or is 2 x 15# sufficient on a 30 year certainteed landmark shingle? (BTW, I am somewhat concerned about adding too much additional weight on my roof)

Thank you,

Marcum


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## titanoman (Nov 27, 2011)

MB1 said:


> I just had two different roofing companies bid my house for a new roof. One says they will not (and cannot anyways) put in ridge venting given a 3:12 roof. They say it is prone to leaking with wind driven rain. The other says they do it all the time and use the best system on the market called Shingle Vent 2. Which do you recommend?
> 
> Also, given that I am in San Jose, CA is it worthwhile going 2 x 30# felt or is 2 x 15# sufficient on a 30 year certainteed landmark shingle? (BTW, I am somewhat concerned about adding too much additional weight on my roof)
> 
> ...


I would think ridge caps could leak, unless they have some product out there for shallow pitches.
What do you mean "2x" the felt? I would think 1 layer of 30lb.

Sent from a Samsung Galaxy S2


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## MB1 (Dec 13, 2011)

By 2x I meant two layers. I spoke with an inspector who said 2 layers have to be used. It can't be one layer of 30# in lieu of 2 layers of 15#. Is the two layers of 30# overkill and will it add much more weight than the 15#?


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## titanoman (Nov 27, 2011)

MB1 said:


> By 2x I meant two layers. I spoke with an inspector who said 2 layers have to be used. It can't be one layer of 30# in lieu of 2 layers of 15#. Is the two layers of 30# overkill and will it add much more weight than the 15#?


It's a Cali thing I guess. And it's no extra weight compared to the weight of the shingles themselves anyway.
Do you doubt the soundness of the structure for some reason?


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## MB1 (Dec 13, 2011)

Well, I have 2x2 inch engineered trusses 24" on center. All the roofers who have walked it say it's solid and they do not feel deflection, but it currently has a 20 year 200 lb per square shingle and a thin single layer of craft type paper with thin tar as an underlayment (and 1/2 or 5/8" OSB). The Landmark is 265lb/sq, and 2 layers of #15 will add to what I have as well. Maybe the 15# vs 30# difference is nothing to worry about. I just don't want to overload it. From what I hear from the inspector, 30 year is very common for re-roofs of these.


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## titanoman (Nov 27, 2011)

MB1 said:


> Well, I have 2x2 inch engineered trusses 24" on center. All the roofers who have walked it say it's solid and they do not feel deflection, but it currently has a 20 year 200 lb per square shingle and a thin single layer of craft type paper with thin tar as an underlayment (and 1/2 or 5/8" OSB). The Landmark is 265lb/sq, and 2 layers of #15 will add to what I have as well. Maybe the 15# vs 30# difference is nothing to worry about. I just don't want to overload it. From what I hear from the inspector, 30 year is very common for re-roofs of these.


2x2 trusses? Anyway, you should be fine.
Are they going over what's there or stripping the old roof?


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## AndyGump (Sep 26, 2010)

> *R905.2.7 Underlayment application.* For roof slopes from two units vertical in 12 units horizontal (17-percent slope), up to four units vertical in 12 units horizontal (33-percent slope), underlayment shall be two layers applied in the following manner. Apply a 19-inch (483 mm) strip of underlayment felt parallel to and starting at the eaves, fastened sufficiently to hold in place. Starting at the eave, apply 36-inch-wide (914 mm) sheets of underlayment, overlapping successive sheets 19 inches (483 mm), and fastened sufficiently to hold in place. Distortions in the underlayment shall not interfere with the ability of the shingles to seal. For roof slopes of four units vertical in 12 units horizontal (33-percent slope) or greater, underlayment shall be one layer applied in the following manner. Underlayment shall be applied shingle fashion, parallel to and starting from the eave and lapped 2 inches (51 mm), fastened sufficiently to hold in place. Distortions in the underlayment shall not interfere with the ability of the shingles to seal. End laps shall be offset by 6 feet (1829 mm).


From the 2010 CRC.

Andy.


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## tinner666 (Mar 14, 2005)

"but it currently has a 20 year 200 lb per square shingle and a thin single layer of craft type paper with thin tar as an underlayment (and 1/2 or 5/8" OSB). The Landmark is 265lb/sq, and 2 layers of #15 will add to what I have as well."

You make it sound like they aren't going to tear the exiting roof off. 
I wouldn't even consider roofing over the existing.
Tear it off! And the Landmarks and felt won't add much weight.

I apologize in advance if I read this wrong.


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## joecaption (Nov 30, 2011)

This has to be a manufactured home, no real house would have 2 X 2's for trusses.


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## titanoman (Nov 27, 2011)

tinner666 said:


> "but it currently has a 20 year 200 lb per square shingle and a thin single layer of craft type paper with thin tar as an underlayment (and 1/2 or 5/8" OSB). The Landmark is 265lb/sq, and 2 layers of #15 will add to what I have as well."
> 
> You make it sound like they aren't going to tear the exiting roof off.
> I wouldn't even consider roofing over the existing.
> ...


That's why I wrote post #6.


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## MJW (Feb 7, 2006)

joecaption said:


> This has to be a manufactured home, no real house would have 2 X 2's for trusses.


With the way the roofing is described, I'm thinking manufactured home also.




FWIW, shinglevent 2 is not the the best on the market. I have pics of it failing within 15 years.


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## Windows on Wash (Aug 30, 2011)

MJW said:


> With the way the roofing is described, I'm thinking manufactured home also.
> 
> 
> 
> ...


What is your favorite?


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## tinner666 (Mar 14, 2005)

titanoman said:


> That's why I wrote post #6.


 Yeah, I see I missed that one. 

For Joecaption and MJW, he said it was a triple-wide in an earlier thread. This subject spans 2 - 3 threads. 

This one mentions the home being a triple-wide.
http://www.diychatroom.com/f9/why-leaking-roof-under-dormer-hole-osb-126477/

http://www.diychatroom.com/f9/weatherguard-v-s-ice-water-shield-priming-first-126705/


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## MB1 (Dec 13, 2011)

Thank you for all the comments and sorry for the confusion I created. Yes, this is a manufactured home about 2000 sq ft, triple wide. Pictures per my post here: http://www.diychatroom.com/f9/help-why-do-i-need-replace-8-year-old-roof-how-correct-problem-126559/. I am definitely stripping off all the old material down to the sheething.

Will also use Winterguard in the dormer valleys, under the dormers, and around all critical areas. And, will skip the ridge venting although will likely add gable venting (unless someone thinks that isn't a good idea?)

Thank you,

Marcum


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## MJW (Feb 7, 2006)

Windows on Wash said:


> What is your favorite?


Omni roll. No baffles to clog up, completely open NFA.


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## kt82 (Jan 28, 2009)

Laminated shingles on a 3/12 are going to leak read the label
use a weatherguard product over the whole roof


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