Subfloor is bowing

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Old 04-07-08, 07:00 PM
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Subfloor is bowing

I am noticing a problem with my 4 year old house. It appears that the plywood subfloor is bowing upward along the seams where the plywood meets. From the basement, I can see that the adhesive used between the joist and the plywood was not used at the seams. This is a ranch home with a full basement in Wisconsin. Any idea what would cause this, and how it can be remedied?

thanks.
 
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Old 04-07-08, 09:05 PM
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The only part that gets glue is along the joists. It sounds like the plywood may be oriented the wrong direction, I don't know why else it would curl up at a seam. Plywood should have the long 8' dimension oriented perpendicular to the joists, not parallel with the joists. So if you look along the joists, there should be a seam every 4' not every 8'.

Is this plywood or OSB (oriented strand board) subfloor?
 
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Old 04-08-08, 04:54 PM
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You talking about the seam you see between each joist or the seam common on 1 joist?

You use the words "appears that...". Either it is or it isn't. What made you aware of this? Like is it causing a raised hump in a linoleum floor? Or did you just look up one day ,while standing in the basement, and think it looks raised?

My initial thought is (if it indeed is really raised) your home has higher humidity than what the plywood was acclamated to when it was installed. And is it like this throughout the house?
 
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Old 04-08-08, 06:49 PM
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thanks for the replies guys. To answer your questions, and to clarify a few things:

1) It is tongue and groove plywood (Georgia Pacific Sturd-I-Floor), and it is oriented perpenidcularly to the joists.

2) I realized that this was happening because I can see and feel bumps in my carpet, so I went to the basement and figured out where the problem was

3)It is only happening in half of the house. The part of the house that is carpeted, I can see 5-6 spots where this is happening. The part of the house where there is laminate flooring might have it, but since it is a floating floor, I might not be noticing it.

My first thought was to nail the subfloor down when I get the carpet re-done. However, I don't know if this would solve it. Another thought was to sand the areas down.

Any other suggestions?
thanks
 
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Old 04-09-08, 04:11 AM
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Hi,

Have you had the carpet steam cleaned? Inadequate removal of moisture from the carpet could cause swelling in the plywood if the wood absorbed the moisture.
 
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Old 04-09-08, 04:35 AM
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Ah, but that would swell the topside more, making plywood convex. We seem to have the opposite.

Relatively more humid in basement? Is either side of the ply sealed in any way?
 
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Old 04-09-08, 09:33 AM
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O-o-o-oh...is this one of those potayto vs. potahto posts?

Is the floor convex (Like the mirrors they use in stores to see if you're stealing) or concave like a shallow bowl or basin?

I understood, from what I read, convex...humped, rising on the surface. Which is it, Johnny?
 
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Old 04-09-08, 06:58 PM
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-Connie, you are right, the floor humps upward.

-I cannot tell if the basement is more humid. I doesn't feel humid to me.

-the floor is not sealed in anyway, on either side.

-It is not the steam cleaning, because there is an area in the bedroom, which also has a hump, that has not been steam cleaned.
 
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Old 04-09-08, 07:33 PM
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Hi Johnny,

It would be simple to tell you to just pull it up and replace it, but it would be better to know what caused the "humps" so it doesn't recur.

Are there plumbing pipes running along there? Is it possible you have a pinhole leak in a pipe? Like when a sink is used, water sprays upward- not enough to notice or drip, but enough
to wet the plywood?
 
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Old 04-09-08, 07:34 PM
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Maybe you simply live somewhere that is readily more humid (even though you might not notice, as you are used to it)and where the plywood came from was not so much. SOMEthing made that plywood grow.
 
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Old 04-09-08, 07:40 PM
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ecman, if that is so, what would he need to do...poly each side of new plywood? That sounds bizarre, doesn't it?

Johnny, I see you've logged off, but do any of your neighbors have this problem?
 
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Old 04-09-08, 08:20 PM
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I can rule out water because this is happening in a few places in the house, some of which have no water lines near them. I originally thought that maybe it was the heat from the HVAC ducts, but the affected areas are several feet away from the trunk line.

Also, of the neighbors I talked to, none of them have this problem.

As for the humidity...I'm in Wisconsin, but can it still be possible that my house may be humid?

I sent an email to a rep from Georgia Pacific (that's who made the plywood) requesting some info (what could have caused it, how to remedy, etc). I'll keep you posted.
 
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Old 04-10-08, 04:26 AM
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Okay, Johnny, thanks...be good to know what the rep. says.
 
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Old 04-10-08, 06:23 AM
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johnny
you say the subfloor is buckling upwards.... you also say that you can see the glue used when looking at it from downstairs....
questions

1. buckling upwards ... does this mean your floor is "floating" or is it pulling nails/screws out from the joists?

2. assume since you can see the glue from underneath that the underside is unfinished -- no drywall ceiling or drop ceiling in basement..... Yes?

3. is your basement floor covered or still just concrete slab?

first comment is something i learned during laying tongue/groove wood flooring..... read a article that a EXPERIENCED floor installer wrote..... his friend did not listen to him and installed all flooring VERY TIGHT and left no expansion room around walls >> during summer time his floor buckled upwards due to wood swelling and having no place to go.... even 1/4" or 3/8" is plenty but since this was not done it ruined this poor guys entire floor.

please advise on the nature of how your subfloor was attached.... having a hard time imagining upwards buckling if subfloor GLUED AND nailed/screwed on each sheet.....

regards
rf
 
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Old 04-10-08, 07:49 AM
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Originally Posted by connie View Post
ecman, if that is so, what would he need to do...poly each side of new plywood? That sounds bizarre, doesn't it?

Johnny, I see you've logged off, but do any of your neighbors have this problem?
Slight gap as suggested. Although, in actual practice I do not know if builders actually do it. I once drove by a house under construction with OSB flooring, and it had rained. I parked my truck and went up on the floor deck to see standing water and the floor was all buckled. Ruined.

I know that on roofs, when I used to build, that it was done more, and was more of an automatic thing because small metal H-clips would be used on the seams that crossed the rafters. The H-clip would seperate the sheets.

Others here more up on building practices today can weigh in on how common it really is that builders leave seperation when laying a floor.
 
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Old 04-10-08, 03:50 PM
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The basement is not finished, so I can get a good look from underneath. I can tell that the carpenters applied glue on the joist, but I can also tell that where the floor rises up, there is no glue.
Additionally, this is occuring where 2 pieces of plywood are joined together. However, this was tongue and groove board, so I asume they did not leave a 1/8th gap.

I was given one suggestion...
Next time I have the carpet up, I could use a skil saw and make an expansion gap b/n the sheets. Is this still advisable with tongue and groove boards?




Originally Posted by rookieRobert View Post
johnny
you say the subfloor is buckling upwards.... you also say that you can see the glue used when looking at it from downstairs....
questions

1. buckling upwards ... does this mean your floor is "floating" or is it pulling nails/screws out from the joists?

2. assume since you can see the glue from underneath that the underside is unfinished -- no drywall ceiling or drop ceiling in basement..... Yes?

3. is your basement floor covered or still just concrete slab?

first comment is something i learned during laying tongue/groove wood flooring..... read a article that a EXPERIENCED floor installer wrote..... his friend did not listen to him and installed all flooring VERY TIGHT and left no expansion room around walls >> during summer time his floor buckled upwards due to wood swelling and having no place to go.... even 1/4" or 3/8" is plenty but since this was not done it ruined this poor guys entire floor.

please advise on the nature of how your subfloor was attached.... having a hard time imagining upwards buckling if subfloor GLUED AND nailed/screwed on each sheet.....

regards
rf
 
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Old 04-10-08, 04:41 PM
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So, you think the plywood is expanding, for whatever reason, and because it's tongue and groove, with no gap, it is rounding up?

If that is what's happening, then yes, cutting a small gap where the plywood meets on the joists for expansion would give the wood room to "come down". You could add some cross blocking to get some bite for the plywood where it doesn't land on a joist.

Still, was it like that from the time you moved in? Are you the original owner?
 
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Old 04-10-08, 06:34 PM
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Do you only have the 3/4 T & G?, or do you have 1/2 " underlayment over that for a 1 1/4 inch thick floor?

I have seen where the reason builders chose the T & G was to short-cut and not have underlayment. If they had used underlayment, they could have used regular ply and then staggered the sheets with the underlayment so that the seams would not be lined up with each other.

If you only have the T & G, then by cutting through the T & G joint, then the plywood can go up and down between tne joists, causing something noticeable above, and also a 'give' in the floor.

But your only option may be in cutting - then trying to rescrew down the seams where you can. You could always nail in blocks from below, at the seams.

At these apts. I take care of built in the 50's, they used 1 X 8 T & G perpendicular to the joists (not diagonally as some did), and then they put tar paper down and then underlayment ply (often now they'll just use particle board) ontop of that. The 1 X 8 joints all have at least 1/8" gap in between. These basements have had a history of getting wet also!, and there have been no flooring issues.
 
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Old 04-10-08, 07:24 PM
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I am the original owner, and have noticed this for the past couple of years. However, there have always been more pressing issues to take care of (a 4-year old and a 3-year old).

I think I will try blocking b/n the joists, and then screw down through the plywood into the blocking. I might try one area w/o cutting through the plywood... I'm a bit apprehensive about doing that.

I probably won't be doing this for a while, though. If I can stand it, maybe I will just wait until we get the carpets redone in the next couple of years. I might get the blocking in now though, as I am also finishing my basement. I will be installing a drop ceiling, so at least it will be accessible.

ecman, I only have the 3/4 plywood.

thanks for the help!
 
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Old 04-12-08, 02:03 PM
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Let us know how your initial experiment works out. Others with same issue may want to know in the future.
 
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Old 04-14-08, 07:56 PM
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It may not happen for awhile, but I will try to remember to do that...thanks
 
 

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