Exterior sheathing mix-up

[robby]

My builder's standard sheathing for the exterior walls and roof is 7/16" OSB. I paid extra to have the roof upgraded to 1/2" (actually 15/32") OSB. The former has a span rating of 24/16, and the latter has a span rating of 32/16.

The framers screwed up. They used the 1/2" OSB on the exterior walls, until they ran out, and then started using 7/16". They then used 7/16" OSB on the roof.

I just brought this all to the builder's attention. He's asking me if I want them to rip off the roof sheathing and replace it with the thicker sheathing, and I told him yes.

My question then is: should I worry about the varying thicknesses of the sheathing on the exterior walls? They differ by 1/32" (1 mm). If I ask them to make them all match, they may just pull off the 1/2" and replace it with the 7/16", instead of vice versa. Or if I wish, they'll leave it, but I'm then stuck with varying thicknesses.

Thanks!

P.S. I asked a related question in the Roof Framing forum, about whether making them replace the roof sheathing is a good idea.

[Rich]

That's a tough call. I don't think you'll notice the difference in thickness and structurally it won't hurt you. What siding material are you using?

[robby]

Vinyl siding over Tyvek.

[Cole]

It souldnt matter.

[robby]

Thanks very much. I guess I'll let that part go, then.

What about making them replace the roof sheathing? Is this a good idea? Will ripping off the sheathing and replacing it damage the roof trusses? Is it worth demanding the roof sheathing be replaced?

[Cole]

To be honest, I dont hink it would make a big difference.

But if you decide to go ahead with ripping it off it wont damage the trusses.

You know what, make them replace it, they screwed it up. Plus you want to know in the back of your head that your house was built to your specifications.

[Rich]

Yes - I would make them replace the roof sheathing also. You paid the additional money for it - you should bet getting what you paid for.

[robby]

Thanks for the replies, folks.

If I were to let the roof sheathing go, they'd give me a credit of either $650 or $900, depending on whether I can get a change order charge reversed as well.

However, I really think 7/16" OSB is inadequate for roof sheathing, which is why I wanted 1/2" at least.

[Tom R]

Yeah, - - 7/16" is a little scary for a roof, - - my absolute minimum is 5/8", - - and that's plywood.

[Zatol]

If it were mine, I would not want the varying differences in the wall sheathing. I think that it will show in the vinyl. If not immediately, then over time. If you leave it as is, you will always (even if it is only in your mind), see a flaw... Do yourself a favor and make the builder build the house as you requested at the beginning and watch him like a hawk for the remainder of the job.

[Dragon]

No offense Zatol but no one is ever going to notice a 1/32" difference in the wall sheathing under siding. Heck, you'll end up with more than that over time with swelling variances from one sheet to the next.

[Tom R]

SWELLING!! :?: - - Oh, - - that's right, - - we're talkin' about OSB!!

Sorry, - - couldn't resist!!

[TnAndy]

Yeah, - - 7/16" is a little scary for a roof, - - my absolute minimum is 5/8", - - and that's plywood.

7/16 is ok for sheathing, but I'm with Tom......as long as you're taking it off, go back with 5/8" plywood....that is what I use also. OSB is crap for a roof.

[robby]

I did want plywood, but the builder wanted an outrageous amount of money for the upgrade.

Also, if I try to change anything at this point, I'll be hit with a $250 change order charge.

In any event, it just occurred to me that the builder may offer to install another layer of OSB sheathing over the 7/16" roof sheathing they already installed to avoid having to rip off the first layer of sheathing. Is this a good idea, or should I have them remove the existing sheathing? Will they be able to find the roof trusses to line up the nails?

Thanks again for all of the replies.

[bkrahmer]

Here is an idea for the wall sheathing: Just make sure each wall is one thickness. I agree about the possibility of the different thicknesses showing through vinyl. As for the roof, I think it depends on what your framing is. IMO, 7/16 is fine for 16" oc, but not 24" oc. Personally, I would go for 5/8 if you are at 24. Putting on another layer would also be fine if they can hit the trusses. You'll have a bit more load, but only about 1.5#, nothing to worry about.

[robby]

OK, I talked to the builder, and he has offered me three options to address the 7/16” OSB on the roof.

Option #1: Rip off the 7/16” OSB and replace it with 1/2" OSB as in the original plans. (This is obviously the most painstaking option.)

Option #2: Upgrade the architectural shingles from 30-year to 50-year (normally a $1,000 upgrade charge), plus a $250 change order credit. (My concern here is that shingles aren’t really a structural member.)

Option #3: Add a second layer of 7/16” OSB to the existing layer of 7/16” OSB sheathing. The builder could not guarantee that they would be able to hit all of the trusses, but they would try to.

Here’s some data on the roof: the roof trusses are 16” O.C. (I upgraded from 24” O.C.) For the original 24” O.C., the roof was designed for 10 psf. With 7/16” OSB, I’m currently at 4 psf, and if they add a second layer of 7/16” OSB, that will put me at 5.5-6 psf.

I asked for 24 hours to make a decision. What do you folks think? I guess I’m leaning towards Option #3. Now that I think about it, I wonder if I can talk him into adding a layer of 3/8” or 7/16” plywood instead…

[VALENT]

I would go with option 3. The OSB will be fine and it they miss some of the trusses it wont be that big of a deal. All the roofing nails will secure the two sheets of 7/16 together very well in addition to the nails that do hit the trusses. By the way, I dont think option 2 is too bad either.

[robby]

Also, I live in central Connecticut, so snow loads are an issue. (This makes me lean away from Option #2, as it adds nothing structurally.)

[Dragon]

I'd do the layover.

[robby]

OK, I’ve been thinking about this all day.

I’m concerned about Option #1, because I’m afraid the framers will do a careless job if they are forced to rip off the first layer of sheathing.

I’m not inclined toward Option #2, because I think the 50-year shingles simply add more cosmetic shadowing, more weight (about 0.7 psf), while gaining nothing structurally.

I’m concerned about Option #3, because I think adding another layer of 7/16” OSB adds a whole lot of weight (between 1.5-2.0 psf) for the strength gain.

So that being said, I’m thinking about asking the builder to add a layer of 3/8” plywood. The weight is much less than the OSB (about 1.1 psf), and plywood is supposed to be better for roofs. Also, the cost for 3/8” plywood is comparable to 7/16” OSB. If he refuses this, I think I’ll go with Option #1.

[Cole]

Go with option 1 and take off that day and be on the job site and oversee them working.

[robby]

Cole, you don't like the 3/8" plywood layover idea? The way you folks disparage OSB for roofs, I'd think you be jumping all over that. :D

[Zatol]

Personally... I do not have a problem with the 7/16ths @ 16" OC..

What type of credit do you get for leaving it as is?

[Zatol]

However, if you just don't want it that way, I'd also choose option 1.

If you overlay, do you think that there is a chance of trapping moisture between the layers?

[robby]

Personally... I do not have a problem with the 7/16ths @ 16" OC..

What type of credit do you get for leaving it as is?
I'd get a $900 credit.

If you overlay, do you think that there is a chance of trapping moisture between the layers?
Maybe...

[Washington nailer]

Did they use plywood clips between the trusses? We have been using 7/16 osb on 24 inch centers for as long as I can remember. Why do you think the 4 x 8 OSB has 24 inch layout marks on it. I say give the framers a break and get any credit from the builder you have coming. Now if it was a tile roof or something I could see 5/8. Man , where are guys from? As for the 1/32 on the walls....... you are not going to see that!

[Rich]

Just because 7/16" works doesn't mean it's right. I've only ever used 5/8" on roofs... and just recently used 3/4" for a concrete tile roof. That doesn't mean 5/8" is right either - but IMO provides a much better product to the owner - if quality is a concern at all.

The main issue here is that the owner purchased 1/2" and therefore should get 1/2".

[Cole]

The main issue here is that the owner purchased 1/2" and therefore should get 1/2".

Exactly. :D

[Washington nailer]

I agree, he should get the credit and move on. There will no problem at all with his roof. Mistakes happen, but to say the framers should have to rip off the whole roof is unreasonable. I work is a very wet area and osb is the only way to go and we have never had a prolem with it!

[bkrahmer]

I don't see why you (Rich) would have a problem with 7/16 OSB. Let's review the functions of roof sheathing... 1. It provides a base to walk on. 2. It holds loads between rafters. 3. It provides structure by tying rafters together. 4. It provides a base to attach your roof finishing materials to. Yep, 7/16 sounds like it fits the bill.

I like to spec one step above code (or minimums). IIRC, 3/8 is rated for 16oc, and 7/16 is rated for 24oc. By using 7/16 at 16oc, that is above minimums. So, what is your argument in saying that using it "is not right"?

[Rich]

IMO minimums are just that - minimums. I'm not in the business of slapping it together to make more money. I'm there to provide the best product to the owner. And IMO that means 5/8". Somebody else says 7/16" - that's their opinion.
I didn't say 7/16" doesn't work.

[Tom R]

Personally, - - I would feel much more confident with a 5/8" roof, - - that it would still be 'sagless' 30 years from now, - - also, - - 5/8" would have more 'nail-holding' power (friction) for the shingles than 7/16".

Around here, - - in Jersey, - - at least in my area, - - OSB doesn't get used at all on roofs, - - walls only, - - and that's more on the 'track' houses.

[robby]

I don’t believe they used edge clips between the sheets of OSB roof sheathing.

I understand that 7/16" OSB meets and slightly exceeds code for 16" truss spacing.

I’d heard that, for a higher quality structure, many builders use 5/8" sheathing, and recommend at least 1/2" at a minimum. So I specified 1/2" sheathing.

All that being said, with a layer of 7/16" on the roof, and desiring the highest quality I can reasonably afford, I’m still torn about what to do.

If I have them overlay another layer of 7/16" sheathing, Zatol brings up the very good point that moisture could be trapped between the layers and cause problems down the road. Is that risk worth taking to get a higher quality roof than my originally specified 1/2" roof? For that matter, does in fact a double layer of 7/16" result in a higher quality roof than a single layer of 1/2"?

There’s also risk involved in making them rip off and replace: pissed-off framers who damage the roof trusses, and do a substandand job on the replacement.

I keep going back and forth…

[Tom R]

The 'moisture-trap' would worry me too, - - and if it did cause a problem, - - it would really be a nightmare doing a double-layer sheathing tear off, - - and I also agree that I wouldn't be too comfortable with pissed-off framers hacking away at my future home, - - if it was me, - - even though my absolute minimum is 5/8", - - with all things considered, - - at this point I would take the credit.

[OSB forever]

I like this thread.

It is getting very interesting.

[Tom R]

Oh-boy!! 'Chip' is back!! :lol:

[Tom R]

Around my way the 'clips' would only be required if it was 24" centers with 1/2" or less sheathing.

[Washington nailer]

Rich said "I'm there to provide the best product to the owner" They make clips for 5/8 why dont you use them. Do you think maybe 7/16 OSB with clips equal 5/8 without? Since you dont use clips do you gap the sheets? Around here when the comp shingles blow off the fastener is still in place. Does the wind in Jersey pull the roofing staple or nail right out of the roof sheathing? I am on the West Coast things are differant here! Your not one of those guys that kept handnailing after the gun was avalible are you? :D

[Tom R]

5/8" doesn't need clips because it can hold itself, - - and I think with 25 years experience I don't need a clip to help me provide a space, - - 7/16" will sag, - - it's simple math, - - 7/16" is only 70% as thick as 5/8", - - and we don't use staples or OSB on roofs in Jersey, - - maybe that's why our shingles don't fly, - - so I really wouldn't know if the nail would come out with it, - - all I know is I provide quality work, - - and to me that calls for 5/8" on a roof, - - with nails, - - and though I have and often use roofing guns, - - hand nailing will provide a better quality job. Lucky for me, - - I guess, - - I'm not in competition with people who do things the cheapest way possible, - - my customers call me because to them, - - saving money means paying just one time.

[Rich]

Ditto Tom - and well said. I'd rather gap a sheet than put those damn clips on.

[Tom R]

By the way, - - I've done roofing in Las Vegas and California, - - the only difference was the running pattern on the strip shingles, - - worked with a guy who 'fumbled' his nails and laid shingles at the rate of 2sq/hr, - - try tellin' him he needs a gun.

[robby]

The 'moisture-trap' would worry me too, - - and if it did cause a problem, - - it would really be a nightmare doing a double-layer sheathing tear off, - - and I also agree that I wouldn't be too comfortable with pissed-off framers hacking away at my future home, - - if it was me, - - even though my absolute minimum is 5/8", - - with all things considered, - - at this point I would take the credit.
After agonizing about this all week, that's what I did. Thanks, Tom, and everyone else for your comments.