# roof sheathing, 1/2 vs 5/8



## weekendwarrior9 (Sep 10, 2012)

Is there any practical benefit from using 5-ply 5/8 ply vs 5-ply 1/2 for roof sheathing? 16" oc 2x10.

I know that 3/4 will add more weight, but my roof structure was engineered to handle a lot more weight than the difference between 1/2 and 3/4.

Plans call for 1/2, but then we decided to go with regular composite shingles rather than the heavier stuff we had speced for (wife found a color of shingle she liked better. And it's half the cost, so i'm not complaining). But since we hadn't sheathed yet, am wondering if there is any benefit for using thicker sheathing. Last longer, more resistant to damage? Or just a waste of money?

Oh, slope is 4.5 per 12, about 21 degrees. Was supposed to be 5/12 but there was a *cough* miscalculation on my part.

California, no snow load here.


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## joecaption (Nov 30, 2011)

Waste of money to use 5/8. Just make sure to use H clips between the rafters.
You do know three tabs are not going to last as long, More likly to lose tabs, will be more likly to leak sooner, and just do not look anywhere near as good.


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## mae-ling (Dec 9, 2011)

Thicker material will stay straighter, not sag between rafters. But really it don't matter.


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## Gary in WA (Mar 11, 2009)

*No* H- clips required with your *16”o.c*. spacing; http://www.strongtie.com/products/connectors/pscl-psca.asp
Unless you live where it rains “cats and dogs”…always check with local AHJ. Be sure to space sheathing a 10d all edges. I had to install 3/4" once, house was in take-off/landing path of airport (sound reduction).


Gary


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## weekendwarrior9 (Sep 10, 2012)

Thanks for replies. I was about to go buy a bunch of H clips, glad I won't need them.

Yeah, 16oc, with blocking at the 4' mark, alternating bays, on a standard gabled roof.

Have 8d 1 1/2" galv roofing nails. 

iirc the nailing schedule is what, 6"oc on all edges, 8"oc for field nailing for the ridge, main roof, and rafter tails, then for the gable outriggers, 4"oc edges and 6"oc field? I've heard I should use ring shank on the gables and rafter tails as well.

Silicon Valley, California, no high winds, moderate rains in winter. What's the gap between sheets for, to prevent buckling?


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## Windows on Wash (Aug 30, 2011)

I would still put in the clips. They are super cheap and do help stabilize the joints in decking.

At the end of the day, what is the cost differential between the the two thicknesses? The thicker deck will lay down flatter and stay more true over the long term as compared to the thinner decking. If both are installed properly, it shouldn't make a different either way but if the difference is $200 in lumber charges, I would do it personally.

I would also not use a 3-tab on my roof when dimensionals are that close in cost...if you were planning on that.


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## sixeightten (Feb 10, 2009)

I wouldn't waste the money using the 5/8. H clips are unnecessary as well. Usually on 16 centers we will use an h clip at each end just to keep the correct spacing. A nail can be used, just remember to pull it out before you trip over it.


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## notmrjohn (Aug 20, 2012)

I use a ring shank or candy coat for entire sheet of sheathing. Use H's their cheap, bit less bounce at seams when nailing shingles. Less bounce with 5/8 than !/2 but with 16" centers probably won't notice. Was re-roofing over old shingles on a house long ago, got a few courses up at one end was getting a lot of bounce couldn't even drive nail. broken rafter? Rotted sheath? Climbed into attic, discover 36" between two rafters. 2X6's Floating joint between next row up of sheathing.


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## Gary in WA (Mar 11, 2009)

Hope you went with a light-colored shingle; http://www.professionalroofing.net/archives/past/mar02/feature2.asp

Under CA Code;* #31*, and footnote *"b"*: http://publicecodes.cyberregs.com/st/ca/st/b200v10/st_ca_st_b200v10_23_par127.htm

You may be under a special seismic "diaphragm nailing" for your location, hit "next section" to progress through them: http://publicecodes.cyberregs.com/st/ca/st/b200v10/st_ca_st_b200v10_23_par168.htm Full-blocking at eves/ridge/gables. Check with AHJ.

Gap is for sheathing swelling when wet due to night sky radiation; Fig. 5; http://www.buildingscience.com/docu...bout-diffusion?searchterm=night+sky+radiation

and "solar driven" moisture, Fig. 3b; http://www.buildingscience.com/docu...t-humid-climates-and-asphalt-roofing-shingles

Gary


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