basement subflooring problem


  #1  
Old 09-05-14, 06:40 AM
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basement subflooring problem

Hi all. Last fall I finished a basement remodeling job. Everything has been fine until just recently. A small 3 foot section of the subfloor has bowed up, probably due to room humidity this past summer ( no air con. in the basement). The system I used was the Delta FL moisture barrier with the recommended OSB on top with minimum 8 tapcons per sheet of OSB. The subfloor was exposed for a good month before carpeting so that I could find any problem spots and refasten. After carpeting everything was fine during the winter and spring but in mid summer I noticed the section of subfloor had bowed up. My plan is to leave it until winter when I will be running the pellet stove to see if it will shrink some. My question is the carpet is a medium pile StainMaster and I was wondering if anyone has ever dealt with this issue and how to fix. Can I run Tapcons directly through the carpet and will they be hidden or do I need to cut the carpet and pad along the bow, screw down and repair the cut. Any experience with this would be greatly appreciated!
 
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Old 09-05-14, 07:12 AM
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Hi montrose,
I cringe at the thought of osb down there, even if they recommend it. From my experience, once it expands it ain't going to shrink back.

You will need to determine if the Delta lifted or if just the osb. Did you seal the perimeter of the Delta or is it open around the edges?

Their web page talks about the moisture normally evaporating into a "dry" basement. With no ac or dehumidifier the moisture issue may well have come from above, basement air. But any imperfection in the Delta install, even those tapcons, could allow moisture to reach the osb.

Let's see what the real pros have to say.

Bud
 
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Old 09-06-14, 05:35 AM
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Perimeter was sealed, seams taped with waterproof tape and all tapcons were sealed with silicon. The Delta is just a lightweight honeycombed plastic that is free to move and should not cause any problem. I think that the expansion is due to room humidity rather than any moisture from beneath.
 
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Old 09-13-14, 12:06 PM
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Still looking for any answers for how to go about pinning this section back down.
 
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Old 09-13-14, 12:34 PM
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While we wait for others to comment, just a little background. When Installing osb as sheathing in a roof or wall it is recommended that you leave a 1/8" gap to allow for expansion. I always thought that was funny as if they wanted the extra gap they should have made the 4x8 sheets 1/8th inch shorter all the way around.

But it is an example of the mfg knowing that the osb will expand if exposed to some level of moisture. From what I have experienced, it is a one-way process with osb and even if it drys it will not go back to where it started. What that implies is some form of relief will be needed as opposed to just bruit force bolting it down.

Can the carpeting be pulled back to expose the osb?

I assume you have considered as a first try to just add more tapcons? Is the areas that lifted between tapcons or has one or more failed?

Bud
 
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Old 10-22-14, 11:02 AM
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Bud I know this a little old but thanks for your thoughts. I tend to agree with all you've said. After lots of dehumidification in that room there is still a bow in the floor. As much as I hate to do it I think I'm going to have to slice the new carpet and padding at that point and cut a thick Kerf in the OSB to "as you said provide some relief and then rescrew both sides down. Hopefully I can get the carpet seam repaired to look new. I should have paid more attention to the OSB gap when laying the floor. Delta probably could have helped if they reminded the installer, in their literature, especially because they recommend the OSB.
 
 

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