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Discussion Starter #1
County inspector failed framing on my garage because the 7/16 OSB sheathing on 24" centers for the roof did not have plywood H-clips. He said an acceptable fix would be to install 2x4 blocking at all plywood seams.

This is fine, but it ruins my plan for insulating the roof with fiberglass, using the foam baffles to leave an air gap for ventilation from the soffit to the ridge vent. The main problem being that what would have been a 2" air gap, will now be reduced to 0.5" because of the installed blocking.

Are there any alternatives to the blocking that I could use? Perhaps something with steel that I could affix to the underside of the seams?

Thanks.
 

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H clips might work

Sounds like inspector may be helping you out here.
H clips add a expansion joint between the osb, those little clips do not really give you support on seams when walking on roof.

I f you butted the osb up tight with no clips, in future the osb will expand and contract, causing the joints to buckle .... may not cause your roof to leak, but can look like crap very quickly.
By adding the 2x4 blocks underneath, may be able to control this ... but just using H clips in first place would have been better.

So inspector feels your pain, gives you an alternative that may work without forcing you to tear the sheathing off and redo it .... and you are asking for a easier way?
At this point, do what the inspector tells you, anything else and he may make you tear it off and do it right.
 

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Discussion Starter #3
Funfool: Thanks for replying, but you're making some incorrect assumptions here. This is a contractor who built this garage for me, one which is well known and well established.

Re-read my post carefully.

I would rather the inspector require me (rather, the contractor) to tear off the roof and do it right. The fact that the inspector gave leeway with the blocking is throwing a wrench into my plans for insulation - which I am DIY'ing.

What I'm asking is if there's any other way besides blocking to correct this - preferably a method which would still allow me to maximize my R-value and required ventilation gap under the roof deck.

Hope this clears up the confusion.
 

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Funfool: Thanks for replying, but you're making some incorrect assumptions here. This is a contractor who built this garage for me, one which is well known and well established.

Re-read my post carefully.

I would rather the inspector require me (rather, the contractor) to tear off the roof and do it right. The fact that the inspector gave leeway with the blocking is throwing a wrench into my plans for insulation - which I am DIY'ing.

What I'm asking is if there's any other way besides blocking to correct this - preferably a method which would still allow me to maximize my R-value and required ventilation gap under the roof deck.

Hope this clears up the confusion.
How about drilling some 1" holes in that blocking so the air can get by. I'm assuming you would use boundry nailing...which is typically 6"...so that gives you some room to put in 2-3 holes.

Just as a side not......if the contractor is so well respected.....7/16" OSB 24" OC? Are you kidding? I don't think I have seen a roof done with 7/16" OSB where it was not sagging....16" OC is marginal...but 24"? The blocking is going to help a lot with the sagging....be glad the inspector wants it.

I did a lot of research on OSB vs plywood for roof....from what I can tell, Plywood is by far much better for a roof.
 

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Using H clips is roofing 101, I'd make the so called contractor redo the roof at no charge.
 

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If the panel rating is 24/0, you need the blocking or clip, if 24/16---- not required, check the panel ink stamp in the attic...unless it is a local code amendment. http://www.apawood.org/pablog/index...n-are-Panel-Clips-Required-for-Roof-Sheathing

http://publicecodes.cyberregs.com/icod/ibc/2009/icod_ibc_2009_23_par100.htm

http://www.strongtie.com/products/connectors/pscl-psca.asp

Gary
P.S. the air channel is for cathedral raked roofs, not insulated attic floor, I may not understand your application.
 

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Discussion Starter #9
Thanks for the super-helpful post, GBR. It is stamped 24/16. Maybe the inspector missed that. Ill double check.

The garage has a narrow 10 foot attic area in the center of the trusses, but is otherwise open to the rest of the garage. I plan on using tools in the space, so i want it conditioned. In other words, it will have a cathedral ceiling.
 

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You are welcome. If you don't need them, you could make your own baffles; http://www.buildingscience.com/documents/published-articles/pa-crash-course-in-roof-venting

The plastic baffles are better than the foam ones that rip on the protruding nails in the roof sheathing. With insulation touching these types/styles baffles, you get thermal conduction= loss of R-value. The rigid foamboard also stops insulation wetting from "night-sky radiation"; http://www.buildingscience.com/documents/insights/bsi-049-confusion-about-diffusion and leaves all the roof sheathing open/exposed to air flow to remove moisture.

Gary
 

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If your contractor is so well established why did he make such a rookie mistake? Make him come back and fix his mistake at his expense. It is his responsibility to do the work to local code. I would be ashamed to leave my customer with this kind of mess.
 

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shouldn't the contractor be responsible for doing thing to code?
This is a DIY site---there is no 'contractor' just a homeowner that is learning and seeking help----

Be helpful---Mike-----
 

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Andy, presuming you mean spray foam insulation on the bottom side of the sheathing when yous aid "unvented attic assembly" that may be the quickest way to please the building inspector after installing the braces the inspector had requested. However won't do anything for sheathing buckling if no spaces were left between the sheets, and also could also possible void and/or limit some shingle manufacturer's shingle warrantys.


oh' Mike the original poster stated he had hired a contractor to build the garage. So the question remains, why is the original poster accepting sub standard work for his/her money invested? Why now does the original poster want to now DIY repair something the contractor, to whom I presume was paid, screwed up?

That is akin to buying a brand new car from the show room floor of a new car dealer, and rebuilding the engine the day you take it home because the engine is knocking.
 

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Discussion Starter #17
Welp, the conclusion is that the county inspector admitted that he erred in requiring blocking on the 7/16" sheathing for the roof (24 OC), since it was rated 24/16 - therefore, edge supports are not required according to the state code.

The county inspector's supervisor indicated that not having the 1/8' spacing would not cause the garage to fail framing inspection by itself.

The tech support rep of the shingle manufacturer said that not having the 1/8" spacing in the roof sheathing would not by itself cause the roof to leak, and if anything, would result in only cosmetic issues with being able to see the sheathing edges through the shingles.

Hard to force a contractor to fix something (sheathing spacing) where both the supervisory county inspector and shingle manufacturer claim it's not broke.

Hopefully this will present no issue in the 3 more years I expect to own this house.
 

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As a few others pointed out, OSB requires 1/8" gap between sheets for proper installation, not suggests- if ink stamped on EACH sheet (sized for spacing); http://osbguide.tecotested.com/pdfs/en/el812.pdf

http://www.apawood.org/pablog/index.cfm/2006/5/15/Tips-for-avoiding-panel-buckling

http://www.ewpa.com/Archive/2006/aug/Paper_266.pdf

http://www.buildingscience.com/docu...nd-the-gap-eh/?searchterm=foam board in walls

Contact the manufacturer of the OSB to check, and get it in writing from the contractor against future problems.

Gary
 

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Code

Have you looked at the IRC? If the panel is an APA rated panel the 24 means 24 inches OC support for roof, 16 inches OC for floor. The clips are for spacing the sheathing. All sheathing requires spacing, both Plywood and OSB. The clips do little to nothing for support. Check the code, or I will if you let me know where you live.

Why didnt your contractor know the code? this is for his account, in my opinion.
 
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