Subfloor in basement which is correct

[Jeremy Biggs]

Well, I'm back, to mooch another answer or two, if you'll have me, Dana

I'm about to order the foam and OSB. I can only find 1/2in OSB that's not T&G, not sure if that is an issue or not? I also came across a post on GBA that suggested using adhesive to attach foam to concrete and then more to attach OSB to foam. I'm not all that certain of my tapcon skills (really any construction skills), so this approach appealed to me. Is there a big risk in doing it that way, long-term? Seems like there is some risk of warping over time with that approach. If I use tapcons, what size/length would you recommend, and best way to make sure they anchor properly?

Lastly, regarding installation, should I tape the foam seams? Should the foam and plywood be butted up to the steel track, or a gap left?

Well I guess that's a lot more than two questions, sorry! Ignore any and all, you've already been a huge help

 

[Jeremy Biggs]

Just wanted to report back for anyone who comes across this thread. Dana rightly let me flounder my way through decisions on best approach for the subfloor, and after much research I decided on 1in rigid foam (taped) and 5/8 T&G OSB attached to concrete with 1/4in x 2 3/4 tapcons. However, when I went to order the T&G I found it was almost $60 per sheet, which was just ludicrous, but I found 1/2 OSB non-T&G for half the price, so went with that, hoping to maybe glue the edges together, but not counting on it. For the actual tapcon process, I found the following links that may be helpful for others:

https://www.greenbuildingadvisor.com/question/basement-subfloor-assembly-details
https://www.confast.com/articles-fastening-wood-flooring-to-concrete/#topOfPage
http://hardwoodflooringtalk.com/forum/tapcon-screw-for-securing-subfloor-t1651.html

I expect to get to installation in the next 30-60 days. I'll try and remember to post back on how that goes.

@Dana, if you're still reading, I did have a question specifically about your recommendation regarding vapor barrier. I've completed the spray foam and rockwool insulation per your instructions, but it wasn't clear if you intended the vapor barrier to be installed in the ceiling, or just the walls. Half of the basement is intended to be ceilingmax drop ceiling (the rest will be drywall), so if you meant to include the ceiling, I'm not sure it's feasible in my circumstance, and if that's the case, maybe the walls don't matter either. I have purchased the certainteed membrain product, and planned to install in the next two or three weeks. Thanks again for your earlier answers.

 

[Sponsor]

 

[Uncgdc04]

Hi all. I posted this as a standalone topic as well but thought I'd tie it to a thread that already was dealing with some of the same issues to see if anyone can provide some input on any of my questions.

I've read the numerous discussions about installing basement subfloors (including this thread), and have especially appreciated the advice in the other threads provided by Dana. I have extremely limited headroom in my basement so I have decided on the following for the subfloor:
a) 6 mil poly on slab, seams taped (I do not have an under-slab moisture barrier)
b) 1/2 inch poly-faced EPS (would prefer more but decided on 1/2 inch due to severely low headspace)
c) 15/32" plywood, tapconned
d) 6.5 mm LVP

I really just have a few clarifying questions:
1) Should the 6 mil poly be directly against the slab or between the insulation and plywood? Seems like either way may be OK, but not sure if there is a preferred way.
2) Should EPS seams be taped (in addition to any seams in 6 mil poly)?
3) Is poly needed if the EPS is already faced with plastic?
4) I will leave a 1/4" gap between subfloor and bottom plate. Should 1/4 gap also be left between sheets of plywood to allow for expansion? I will be using standard plywood, not tongue and groove.
5) My walls are already built and drywal attached, so I can not take poly to the foundation walls. Should I try to attach/seal the 6 mil poly to the bottom plate?
6) Any reason to use laminate flooring over LVP? Seems I read something about the "perm" levels in the floor covering making some difference but can't seem to locate that info.

Jeremy Biggs - I'd also be interested to know if you have any thoughts on the above based on your experience as well as how the tap con process went. Did you use hex head and countersink them?

Thanks for any and all advice!

 

[Robert Ransom]

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