Quick basement reno question before installing platon subfloor

fitzskiOctober 30, 2010

I'm finishing my basement, and I'm about to put down the dimpled platon as the subfloor (with 4x8x3/4 T&G OSB on top), and have a quick question.

Would it be a good idea to put a vapour barrier that transitions from the floor to the wall? That is, have plastic sheeting that extends 6" under the platon, and runs 6" up the wall, sealed with PL Acousti-Seal?

Perimeter walls are poured foundation with 2" foam board (O-C Celfort 200) glued on (PL300). Once the floor is down, 2x4 stud walls will be framed and insulated against the foam board. Just wondering if it's a good idea to do something now - that's cheap & easy - to mitigate any potential moisture from migrating from the slab to the stud wall.


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The space is important as it allows vapour under the platon to gradually escape into the basement. See Platon Installation Guide www.systemplaton.com/pdf/ARM-Platon-install.pdf For the best protection of the stud wall from moisture you can put the base plate on top of strips of 1" XPS.

    Bookmark   October 30, 2010 at 1:45PM
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2" of XPS is R10. Unless you're in the Lower Mainland, I'd add further insulation between the joists--either fibrous or EPS or XPS foamboard, depending on your budget. No vapour barrier is needed, according to Building Science Corp., though your local building inspector may still insist on one.

    Bookmark   October 30, 2010 at 2:14PM
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Thanks worthy!

Yeah, I wasn't thinking it was "necessary", but just thought "well, maybe there's a good reason to do it, and now is the time!". I'll skip it.

Yes, stud wall will be insulated with Roxul (R14) on top of the XPS, so R24 on the walls. No vapour barrier, per Building Science.

I'm not really concerned about moisture, so I think I'll still build the stud wall right on top of the OSB flooring. The 1" XPS is a good suggestion, though - any reason why that instead of typical foam gasket?

    Bookmark   October 30, 2010 at 3:03PM
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any reason why that (XPS) instead of typical foam gasket?

As you're putting the plates on top of the OSB, which is on top of the Platon, there's no need for an additional thermal break or vapour protection.

If the wall were framed separately, the foam gasket would not be appropriate. Strips of 6 mil poly would be better; it comes in rolls for just that purpose, usually black. I use the XPS instead of the poly as it keeps the wood away from any minor flooding that may occur--broken pipes, washer connection, water tank etc.

The R24 will make for a very comfortable basement!

    Bookmark   October 30, 2010 at 4:22PM
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Ready to remodel my basement and have a few questions. Any help would be much appreciated. Home was built in the 50�s with a partially below grade basement (approx. � below and � above. I do not think that I have a major water problem but I�m going to wait a few months to begin the work just to be sure. But being a basement, it�s a little damp and is some areas, there is a white powder just below grade that I�m assuming is water seepage. As of now, the basement is completed gutted and I�m watching it closely. If all goes well, I�ll start the renovation in early spring. The plan is to use a Dricore or a Delta FL or a Super Seal membrane on the floor (leaning towards the Delta FL or Super Seal because it seems like it would work better as a moisture/vapor barrier. Also, I read here and there that Dricore has potential to mold due to the fact that the bottom has exposed particle board edges.). Then, now here�s the big question, I wanted to hang a dimpled membrane (Delta FL or Super Seal) from the wall at a height TBD (obviously above grade but if I went a little higher, I can from the wood just below the floor joists. Seems easier to screw into the wood frame than the concrete wall). I would bring that down to the floor leaving an inch or two return on the floor and install the floor on top of the return, taping the seams where the floor meets the wall (and everywhere else). Then I would use some sort of rigid insulation on top of that, stud on top of that and green sheetrock on top of that. Does this seem like a good idea or is it a recipe for disaster because there is no where for the moisture coming thru the walls to go (it will be trapped btw the concrete wall and the membrane barrier. Super Seal advertises that their membrane can be used in interior applications but with a French drain installed. I do not think that I�m getting that much water that would justify the cost or need for a french drain. There are also 2 schools of thought on how to install these products. Completely seal it with spray foam to block any airflow and the other suggests leaving a � inch gap where the wall meets the floor to promote airflow. I�ve been looking around and no one seems to be doing what I want to do. One last thing, I will frame out a 5 X 10 boiler room in the corner of the basement that I will not be installing the wall membrane or a floor system to. Is this good or bad? (considering the airflow question). Thanks in advance.

    Bookmark   January 18, 2012 at 1:05PM
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