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  1. #1
    Join Date
    Jan 2011
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    Default Not Thinking Clearly About a Subfloor

    Hey experts, I hope you can help me. I plan to install a subfloor in my unfinished basement by laying down 1" polystyrene sheets directly onto the concrete floor and then covering them up with 5/8" OSB fastened down with Tapcon concrete screws.

    Here's where I'm not thinking clearly. I plan to enclose my utilities (i.e. furnace, hot water tank) by building a room around them with partition walls. Do I build the partition walls first and then build the subfloor up to the partition wall? Or do I build the subfloor first and then build the partition wall on top of it? If I did that I'd have to somehow continue the subfloor under my furnace...I don't see that happening.

    If I build the subfloor up to the partition wall, I would then have exposed concrete floor in my utilities room. Any issues with moisture developing on the concrete floor in the utility room since heat from the surrounding rooms could penetrate the wall and condense on the cold concrete floor?

  2. #2
    Join Date
    Jan 2009
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    Needham, MA
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    Default Re: Not Thinking Clearly About a Subfloor

    you're going to get about 10 different answers from this question but here's my first and second choices. #1 if you're going to carpet the floor i would use "Dricore" panels on the floor. it works as an insulator over the concrete and a vapor barrier (however some will disagree with that). the panels come in 2'x2' squares and fit together with a tongue and groove. nothing could be easier for a DIYer to install and the comfort level is great under a carpet. #2 if you're putting down hardwood flooring i would do something in the realm of what you're doing. i would frame any walls first with PT as the wall baseplates to rest on the concrete floor. i would not put any sub floor under the walls because if you ever get water in the basement via nature or a broken pipe, you won't have to rip out the walls to replace the sub floor. as for a utility room i would never put any sub flooring in there, it's an accident waiting to happen.

  3. #3
    Join Date
    Jan 2011
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    Default Re: Not Thinking Clearly About a Subfloor

    Quote Originally Posted by MLBSF View Post
    you're going to get about 10 different answers from this question but here's my first and second choices. #1 if you're going to carpet the floor i would use "Dricore" panels on the floor. it works as an insulator over the concrete and a vapor barrier (however some will disagree with that). the panels come in 2'x2' squares and fit together with a tongue and groove. nothing could be easier for a DIYer to install and the comfort level is great under a carpet. #2 if you're putting down hardwood flooring i would do something in the realm of what you're doing. i would frame any walls first with PT as the wall baseplates to rest on the concrete floor. i would not put any sub floor under the walls because if you ever get water in the basement via nature or a broken pipe, you won't have to rip out the walls to replace the sub floor. as for a utility room i would never put any sub flooring in there, it's an accident waiting to happen.
    Thanks for your response. So if I build the partition walls first and then construct the subfloor around the partition wall, I will have about a 2" step down into the utility room. What can I use to make the transition between subfloor into utility room more seamless?

  4. #4
    Join Date
    Jan 2009
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    Needham, MA
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    Default Re: Not Thinking Clearly About a Subfloor

    you can just cut an angled transition piece with a piece of PT 2x4. it's only a utility room, so you can get as fancy or non-fancy as you want. just make sure whatever you put against the concrete is PT so you don't have to worry about moisture rotting the wood.

  5. #5
    Join Date
    Mar 2010
    Location
    Canada
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    Default Re: Not Thinking Clearly About a Subfloor

    Using extruded ( XPS ) foam covered with 5/8 plywood has been a choice for nice warm basement floors in these parts for a while. Excellent thermal break and provides nice softness to an otherwise hard concrete basement floor.

    Dricore has been used around here for a few years now and it's decent product, but ,it is somewhat pricey. However, the product is fussy to work with. Things like the uneveness of the base can't have more than 1/4 inch dips otherwise you need to level the base. The panels are have the same considerations as a floating floor like climatizing before installation , minimum gaps along perimeters , gaps left between floor and base trim , among others. When installing carpeting there is a specific fastening method to secure the system down , preventing things shifting when the carpet is being stretched.
    It's important to follow installation instructions very closely for the product.

    Oddly enough it reminds me of the way sub-floors were laid in basements before Dricor.
    Dimpled plastic sheathing ( same used for foundation waterproofing ) was laid first then plywood laid on top fastened through to the concrete.
    Whether or not this is the inspiration for Dricor I can't say , but sure looks that way.

    Regardles which product(s) used for the sub-floor , it's by far easier to lay the floor first then build your walls on top.
    Normally the flooring continues into the utility room but stops short around the furnace and water heater. There is no worry from condensation issues with the exposed concrete.

    If you do build the the walls first you don't need to use pressure treated for the bottom plate. All that's needed is a isolation barrier between the concrete and untreated lumber. The isolation barrier can be poly or sill seal gasket.

  6. #6
    Join Date
    Mar 2008
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    nova scotia, canada
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    Default Re: Not Thinking Clearly About a Subfloor

    the dri-core product is great, ive used it several times and prefer it to laying 2x4 sleepers then laying foam between then sheathing it. and yes to framing the walls first, dont forget to use pt lumber for your footers or put plastic under it so its not in direct contact with the concrete floor. if you still want a finished floor in the utility room, ceramic tile direct to the concrete is the simplest most durable

    myself personally havent done the foam down first then plywood tapcon it down. i have several friends who have tried it and found it very slow and the tapcons dont always grab.
    fire up the saw and make some dust

  7. #7
    Join Date
    Mar 2010
    Location
    Canada
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    86

    Default Re: Not Thinking Clearly About a Subfloor

    I don't find the foam/plwood slow going , mind you there is the dril/drive of tapcons. Dricore still takes some time to fuss with the gaps and there is some drill/driving tapcons when laying wall-to-wall carpet.

    Tapcons don't always grab?
    Sounds more like an installer issue there. Out of the hundreds of tapcons used I've never had any issues of not grabbing.

  8. #8
    Join Date
    Mar 2008
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    nova scotia, canada
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    Default Re: Not Thinking Clearly About a Subfloor

    with the tapcons, ive taken every step and they either dont grab or they snap. i dont know if its more to do with the old concrete mix, the old timers around here use to use beach sand which didnt make for very good concrete

    ive found it more efficient and cost effective to simply use tie wire and a spike for fasstening wood to concrete. in situations where strength is required i use expansion bolts
    fire up the saw and make some dust

  9. #9
    Join Date
    Jan 2011
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    7

    Default Re: Not Thinking Clearly About a Subfloor

    This is an excellent thread for me, since I'm about to start finishing my basement off. (1600 sq. ft.)

    I haven't decided if I'm going to do DriCore or foam/ply. I bought 12 DriCore panels for a test area, and they seem to be solid enough to take furniture and to walk on. It was mentioned that carpet might be an issue with them, but what about drop-in-place carpet squares? (the kind with padding on the back)


    I have a question, though, about existing floor drains. I'm pretty sure I can't just cover them up, can I? How do I handle this?

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