Bowed studs under OSB.

[mvm313]

Hi,

I need some advice. Allow me to give a little background first. My family and I are having a new home home built (on a slab). We will have a brick exterior upon completion. Presently the house is sitting with the OSB and moisture wrap on the outside and sheetrock on the inside. We were checking the house out yesterday and noticed the OSB on the southern side of the house is bowing outwards in three spots. The bowing is sginificant. I didn't measure, but I would guess that it bows about 4-5 inches from center in each spot. We spoke to the building manager and he said that the framing studs are the cause. He says that it is common for this to happen but because we have a brick exterior it shouldn't be a problem. He also checked to make sure that the sheetrock on the inside isn't bowing as well, and it isn't. From what I gathered, if a stud does begin to bow prior to the sheetrockers coming in, he has the framers toss another stud up in front of the bowed stud and nail the sheetrock to that. The site manager also says that the stud can't bow much more than it is, because it would have to pull the away from the slab to do so. He seems to be more concerned about the aesthetics. My concern is the structural integrity of the home (or any other problems it could cause). Is it worth it to delay completion for them to open the walls and replace the three studs? Will fixing the studs help or will it cause more problems? Thanks
in advance for the advice.

Mike

[mjpliv]

If you have a wall stub with a noticable bow in it, have it replaced. If your brick veneer only has a 1/2" to 1" airspace then your mason is going to have an interesting challenge to install it!

If the drywallers have to sister in a stud straight enough to attache the drywall then something is seriously wrong with the original stud, either moisture or structural flaw.

Is this a 2x4 or 2x6 exterior wall?

You are paying for quality materials and quality workmanship! Make sure you get it!

[Rich]

I agree with mjpliv.. your home is probably the single largest expensive you'll make. It should be constructed correctly.

[NAIL BENDER]

This is probably not due to a bowed stud. What probably has happened is this: When sheeting a wall with OSB, you must allow 1/8" min. between sheets. When water enters the OSB, the sheet swells quite a bit. If the OSB is put up tight the opposing sheets will swell and press against one another and bow out the OSB between the studs. If it is bowed as much as you claim, it will also show on the interior sheetrock.

[Tom R]

Tell him you want the OSB replaced with plywood. Quality houses use quality materials.

[Rich]

I'm doubting that 4-5" is from expansion of the OSB. I would say that worst I've seen from expansion is about 1" where there was full ladder blocking across a seam.
Tom R - I wish everyone would use plywood. The project I'm currently working on is using 3/4" exterior grade A/C seven ply.. it's fantastic to work with - albeit heavy as you know what. We got an excellent deal on it - $20 / sheet :) and about 35000sf of it.

And welcome to the forum.

[NAIL BENDER]

I'm doubting that 4-5" is from expansion of the OSB. I would say that worst I've seen from expansion is about 1" where there was full ladder blocking across a seam.
Tom R - I wish everyone would use plywood. The project I'm currently working on is using 3/4" exterior grade A/C seven ply.. it's fantastic to work with - albeit heavy as you know what. We got an excellent deal on it - $20 / sheet :) and about 35000sf of it.

And welcome to the forum.

I would doubt someone would put in a stud that was bowed 4-5" also. More than likely a bit exaggerated to make a point. I have seen OSB that has been highly saturated with water bow out at least 2" between the stud bays. OSB really isn't that bad if it is put up correctly and doesn't sit exposed to the weather for too long.

I'm glad to be here, Thanks. Joe

[Rich]

That's true too.. but sometimes you just never know what some people will do :)
I don't mind OSB at all.. I install what the client wants.

[NAIL BENDER]

It would be easy to tell by the way the sheetrock looks on the inside. :wink: So mvm313, is the sheetrock bowed on the same stud? Just curious.

[Tom R]

I believe he stated in his original post the the sheetrock on the inside is fine. I'm wondering if perhaps the wall was sheathed from both ends towards the middle, and then that 'middle' sheet was 'jammed' in, then it also swelled. Personnally, I think the 'swelled' OSB is only 'half as scary' as the building manager trying to 'blow it off' as a non-problem. Isn't there some kind of law against 'impersonating a carpenter'?

[Tom R]

Rich,

Thanks for the welcome to this great site. I can learn a lot here, maybe even throw 2 cents in here and there. That is a 'great' deal on the plywood.

[mjpliv]

I try to keep an open mind when approaching these threads and try to look at all of the materials used in an assembly that may fail to meet the homeowner's expectations.

There is always the possibility that the OSB sheeting, if installed incorrectly, could cause a wall section to bow. I doubt this was the case here because the wall was bowed in a couple of places only. Generally, if an error was made in the installation (ie - no gaps between the sheets) then one would suspect that the entire house lot of sheathing was installed the same way.

Lets look at the physics (geometry?). For the for a stud to bow, one edge must be longer than the other. For the OSB to be the cause of this bow it would have to either stretch the edge of the lumber it is nailed to or crush the other. Considering the fact that we are dealing 1/2" of material nailed to the stud with, at best, one 2-1/2" nail or staple every 12", I find it difficult to believe that the OSB could actually cause anything more than a minor distortion of the wall stud before the fasteners failed. I think it is more likely that the nails would pull out of the stud or pull the heads through the OSB.

I truly suspect that this bowing was caused by uneven drying of the wall studs causing one edge to shrink faster than the other. This may have been caused by the exterior sheeting (in this case - OSB) being exposed to the elements for too long and is wicking the moisture into the adjacent stud. But this would have happened just as easily and with the same results as plywood sheathing or good ol' matched lumber (T&G boards).

My question to the home owner is "are the studs stamped as KD (kiln dried) or SD (surface dry) or GR (green)?"

I am pretty sure that the choice of sheeting material is irrelevant in this case.

[mjpliv]

For Rich -

What is A/C designation on the plywood you are using?

For everybody -

When I was in St. Pierre & Miquelon (a couple of small islands between Nova Scotia and Newfoundland that are territories of France) dealing with some construction issues over there they were building to the European standard which is 3/4" good one side fir plywood on the exterior walls and 1/2" good one side on the interior walls.

Talk about a solid structure! :shock:

[Tom R]

To mjpliv,

Although you're welcome to disagree with the 'jammed OSB' theory, you're taking 'for granted' the stud itself is bowed, I'm 'taking for granted' it is not. And if the sheathing was installed from two sides towards the middle, the 'bowing' would only 'happen' in a 'couple of places'. I do agree the nails would 'pop', in no way would the stud get 'pulled with it', but then, I don't think it's the stud to begin with, the 'manager' started that rumor.

[mjpliv]

True enough! We all have our theories on the cause of the bow in the wall surface. The only way to know for sure is to open the wall cavity and check.

If it is the fault of incorrectly installed sheeting then replace it or cut the missing expansion spaces between the sheets. If it is the fault of wet or flawed studs then replace them and make good the wall assembly.

And I think we, myself included, forgot all about mvm313's simple request. I think he/she may have been less concerned about what caused it then what should be done about it!

So mvm313, my advise to you tell your contractor to make good the wall assembly, to your satisfaction, regardless of the cause.

[Tom R]

Ditto, and afterwards, let us know. We'd all be very interested to know the cause of this 'unusual' situation. Good Luck, and 'stand your ground'! (Don't 'timidly question', - - rather 'politely demand').

[Rich]

For Rich -

What is A/C designation on the plywood you are using?

AC - A side is sanded with little to no defects.. C minor imperfections I believe.

[Tom R]

Correct - ratings are A, B, C, and D. For instance, the standard roofing plywood would be CDX, (C-side, D-side, eXterior glue).