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Old 01-14-2019, 12:43 PM   #1
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What should I use to fill large divets and small gaps in OSB subfloor?


I'm installing subfloor on which I intend to put Drop-and-Done vinyl directly on top. The Drop and Done is thin (3/16") and very flexible, so I assume we'll feel every little flaw in the subfloor. There are these "wonderful" divets in the ends of every sheet of T&G OSB from HD (picture attached) that need to be filled.



My question is - what product should I use to fill these? The divets are 3/8" wide and ~1/2" deep.



Also- how anal should I be about filling small gaps where the OSB didn't quite fit together - some gaps are maybe 1/4" wide, most are ~1/8", but otherwise the joints are flat.


Thanks!
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Old 01-14-2019, 04:17 PM   #2
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


While I'm not familiar with that flooring it's commonplace to first install 1/4" underlayment over the subfloor and then put the vinly over it. The joints would be staggered from the subfloor joints.
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Old 01-14-2019, 05:43 PM   #3
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


Bingo, what Mark said. You need underlayment for vinyl flooring. And when done, seams need to be super smooth. Deep nail divits filled. These thin vinyl floors telegraph everything from below. Especially in traffic areas.
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Old 01-14-2019, 05:52 PM   #4
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


Thanks for the advice, 1/4" ply is easy enough. Any thoughts on what I should fill any holes and gaps in it with? Wood filler is so expensive...maybe DAP Plastic Wood, or would that be overkill?
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Old 01-14-2019, 06:10 PM   #5
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


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Originally Posted by jsand View Post
Thanks for the advice, 1/4" ply is easy enough. Any thoughts on what I should fill any holes and gaps in it with? Wood filler is so expensive...maybe DAP Plastic Wood, or would that be overkill?



Floor leveler. Usually comes in powder form, mix up what you need, apply with a putty knife. let cure thoroughly, sand lightly. Ready to tile.
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Old 01-14-2019, 06:20 PM   #6
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


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Originally Posted by jsand View Post
Thanks for the advice, 1/4" ply is easy enough. Any thoughts on what I should fill any holes and gaps in it with? Wood filler is so expensive...maybe DAP Plastic Wood, or would that be overkill?
Use the right product.
Ardex feather finish is best. Or if from the box store try.
https://www.homedepot.com/p/Custom-B...SF10/100152565

Also goggle the nailing pattern for the 1/4" underlayment. By the time you mess with the cost and installation.
You are not far from the cost of just installing a better floor without the underlayment needed for the thin sheet vinyl.

Look at the lifeproof LVP at homey depot.
Still should use a patching compound.
Anyway gives you something to think about.

Next time pass up the OSB T&G and get the Advantech T & G which already has a good finish.
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Old 01-15-2019, 04:24 AM   #7
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


I have used a setting compound like Durabond to fill the seams and staple holes on the underlayment but then I do more walls than I do floors ..... and I always have some Durabond on hand.
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Old 01-15-2019, 07:04 AM   #8
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


And FYI those "divots" are standard on OSB subfloor plywood. They are drainage grooves so water doesn't get trapped in the butt seam during rain (new construction). Yes, use underlayment and next time use advantech or an underlayment grade 3/4 plywood.
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Old 01-15-2019, 07:32 AM   #9
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


Quote:
They are drainage grooves
Unless it is something proprietary, I gotta call the BS police on this one. Seldom is OSB used as a subflooring during construction so weep holes would not be factored in the manufacturing. Advantech is made for that and should be used. Durabond is a good filler and quite a bit less expensive than wood filler. I wouldn't worry about the boogers on the subflooring, since it will be covered by the underlayment.
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Old 01-15-2019, 10:23 AM   #10
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


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And FYI those "divots" are standard on OSB subfloor plywood. They are drainage grooves
That's whack!!
Most likely this sheet was top or bottom of the pallet, metal band cut a groove.

Side note, I only see OSB for subfloor on a typical house, 1/2 price of Advantech and the roof is usually up quickly.

On this new thick vinyl planking, supposedly you can patch/sand and install over the exist T&G. Personally, I would always install "underlayment" (not 1/4" plywood), as rough-in framing ain't pretty. Especially when you put glue down. It's costly, but a good APA rated underlayment will save you bumps (literally) down the road. APA because its going to get wet from the glue.
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Old 01-15-2019, 11:23 AM   #11
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


Here is one example of a OSB subfloor drainage hole.
Note that the edge of the OSB has been inlet slightly to allow for drainage.
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Old 01-15-2019, 11:47 AM   #12
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


Qucik tip on installing the thin underlayment. A narrow crown pneumatic stapler will make the job go so much easier. The nailing grid on these thin sheets is between 4 to 6" and closer around the perimeter. So you are easily looking at 150+ fasteners per sheet.
I would concede that a ring shank flooring nail is the very best fastener choice, but the narrow crown staples are adequate and so much quicker.
Do not use glue, you might want to pull it up some day.
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Old 01-15-2019, 01:24 PM   #13
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


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Do not use glue, you might want to pull it up some day.
I think this product uses a pressure-sensitive glue just to keep it from sliding, so it pulls up. I try to stay away from these new-fangled fancy-dancy products until they've been time-tested anyway.

That "drain" hole, how does that work in T&G, especially glued? Why would a ply manuf. design for POOLING water on a temporarily exposed subfloor? I have to look this one up, I still think its whack.
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Old 01-15-2019, 01:41 PM   #14
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


Actually, they do look like drainage slots. There are two on every single board and they are very regular. They are on the 4' ends, not the T&G sides. Seems very odd to me too.


Yes, the Drop and Done uses a pressure sensitive glue, and only around the perimeter so at least I wouldn't be applying wet glue everywhere. I'm really kicking myself now for going with OSB - I don't know why I thought it was fine, but I spent a LOT of time reading about subfloors (mostly focused on damp basement approaches) - I don't remember reading about Advantech or using treated ply. I read more than one place that OSB is fine, but who knows what qualifications those folks had! Or maybe I was reading what I wanted to read since OSB is so much cheaper.


So .... now my problem is that if I raise the floor another 1/4", my lower stair step is going to be out of code. Not to mention the time and another $500 (both relatively minor).



Thoughts/experience on other approaches to making the OSB okay? Maybe skim coat with a sealant? I don't really understand how it can expand and contract enough to cause gaps/buckling when it's screwed down, but I recognize I'm a naive newbie.
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Old 01-15-2019, 02:21 PM   #15
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Re: What should I use to fill large divets and small gaps in OSB subfloor?


Also, before the obvious question comes up - we did not put OSB in contact with the basement foundation. We did a lot of research and ended up installing a dimpled plastic underlayment on the concrete to allow vapor pressure to release from under the subfloor (similar to DMX) with the OSB over that. Basically, creating a better version of Dricore.
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