Pressure treated 2x4's touching concrete floor

Old 05-01-03, 06:28 PM
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Pressure treated 2x4's touching concrete floor

For some reason, despite having taken some community college classes on home improvement and reading a fair amount of those DIY books, and reading my village's special code requirements (village made no reference to needing it), I completely missed any reference to needing to put "green/weather treated" 2x4's against my concrete floor while framing my basement. So I now have 4 large rooms, closets, bathroom, hallway, storage area, etc., completely framed out, well over 1000 squre feet, and I only have regular 2x4's touching the basement floor. I did place a thick layer of plastic sheeting, though, between the base of all my framed walls and the concrete floor, as well as along the foundation walls.

1) Is not having used weather treated 2x4's on the base of my framed walls a big deal? My basement is bone dry and always has been. I did the test several times where you tape aluminum foil to the concrete floor and foundation walls, and not one drop of water ever showed up underneath the taped area, despite the wettest spring on record.

2) My sump pump does run quite often (once or twice an hour for 20 seconds during heavy rains), but I plan on buying a back-up sump pump (electric/battery powered) to avoid any problems with the basement flooding even under the most extreme circumstances.

The walls right now are framed, with no electrical or plumbing or insulation started yet. Should I start cutting out the bottom plates and replace them with treated lumber now (at great time and expense), or just let it go? If my basement remains completely dry now and forever, will that plastic layer be sufficient? Are my base boards going to rot away no matter what I do if I don't use treated lumber?


P.S. I found this site by accident very fortunately, and I am very thankful for the timely/informative answers I have received with previous posts. I thank you guys/gals in advance for your time!
Old 05-01-03, 07:14 PM
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I guess this is the best and most economical way to construct walls that would be placed on the exterior. I prefer to see 2x4 but as mentioned by others they can get 2x3's. You still need that W/T plate. Doing the framing 16" O.C. provides a solid base for your 1/2" drywall. If using traditional framing method, frame your new wall 1" from the vertical block/masonry surface if using R-13. The reason to keep the wood out from the walls is the moisture that could damage them. If using insulation like R-19 and only 2x4 studs, the insulation would touch the walls. I have stated before that if a homeowner did put thicker insulation in, and the wall was only 1" from the masonry surface, I have recommended hanging a vapor barrier between the back of the wall and masonry surface. This doesn't allow for the insulation to touch the wall and air movement is not restricted but at least you won't create damage to the insulation or wood.
Vapor barrier should be placed directly under the drywall. The warm inside air containing water vapor can get past the wall finish and insulation and condense inside the colder wall cavity. If enough of this happens, and the water cannot escape, wood rot, mold, and other moisture-related problems are likely to occur. For this reason, building codes often require installing a vapor diffusion retarder on the warmest side of the wall cavity. This is what is required in Minnesota;

"A 4 mill poly vapor barrier must be placed against all concrete or block exterior foundation walls prior to applying furring strips for full height of the wall. Another 4 mill poly vapor barrier must be placed over furring strips and insulation prior to covering with finish materials. (State Energy Code Requirement)" - MINNESOTA CODE


If you do want to increase the R value, move the wall out further or use the R-13 and then apply a rigid insulation over the studs (warm side) then drywall (not paneling) *Code advises a 15 minute fire rated material over any rigid insulation - 1/2" Drywall*..

Kraft Faced insulation is fine to use in the above scenario. No need for the poly and you can do everything easily. You may find this easier and I would do this versus unfaced and vapor barrier because I don't like to play with it any more than I have to.

Let me add one other thing, rigid insulation used on a concrete/masonry surface is fine. Considerations to make in using this is;

1. If you are just using 1 1/2" rigid and furring strips - A. You need W/T strips to protect the wood. B. The strips can be adhesively applied but they must be solid - mechanical anchors may have to be used to insure that if shelving is installed it will hold. Problem with this is, the penetration into a sealed concrete/masonry surface is damaged and subject to leaking. C. Any electrical boxes will have to be shallow - sometimes makes it hard to wire. D. You must use a fire retardant material over this as per Code.

(Most books, articles about rigid and furring strips fail to say anything about the use of W/T and this will get destroyed and be a good source for mold/mildew with the slightest hint of moisture)

2. Alternative which does add cost is to apply full rigid sheets to the concrete/masonry walls, adhesively applied, then place frame wall against the rigid, then insulate between studs and cover with drywall. The Rigid insulation does then act as a the vapor barrier. Do not tape/seal the seams. This allows it to breath and dry up any condensation that may form.

So here is some more stuff....

W/T is wood treated. International Residential Building Code says "it must be used whenever wood is in contact with concrete and/or masonry". Check it out with your local inspector. This would also include furring strips applied directly to a vertical block wall unless you use the vapor barrier behind it.

If you are considering using 2x2's as furring strips I can only give you my 2 cents worth and you decide;
A. Are you going to have electrical in the walls? Short depth boxes make it difficult to wire. 2x4's would be better. B. Are you planning or foresee hanging shelves or cabinets on the exterior walls? Not alot of strength and may be subject to splitting easier than 2x4's.
C. I personally can't seen how 2" will make a difference in conserving space when you consider the hassle of doing electrical or other carpentry issues.
D. Depending on what you are talking about when it comes to the pre-cut polystyrene, the white foam board, which is the molded expanded polystyrene (MEPS) only is available in R-2 - 3/4" thick, it only costs about $5 per 32 SF. The better quality with R-7.5 is the pink foam - extruded expanded polystyrene (XEPS). This is great stuff but costs more.

Just a note, when you use NON-W/T stock as the 2x2's or 1x3's as furring strips, you have to place a vapor barrier between that and the block wall - you have to attached the furring strips to wall somehow, right? You can't adhesively apply them, you have to use a ramset - this obviously has just put a hole through the poly making it useless which in turn starts the problem with moisture touching the wood. Second, is if you used W/T or Non-W/T stock and have a waterproofing sealer on your block walls, you just penetrated the block, puncturing the seal coating that was suppose to stop water/moisture...creating possibly a worse problem....water that fills the concrete block cores starts to drain out or will leak in heavy rains. Just thought I'd bring this up. I would do 2x4 walls with R-11 or R-13, insulation would cost about $.02-$.03 more per square foot than the white foam and be better all around. Leave the walls out 1" from the block when framing, apply your poly over the studs apply the drywall and be done. You'll have no problems then.

Hope ths helped!
Old 05-02-03, 05:51 AM
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I did the same thing! Framed everything with regular wood.... I've decided to leave mine alone and take my chances. The floor is painted with epoxy, and there is a poly vapor barrier under the concrete slab. Never had a moisture problem in the basement. Many others I have talked to have taken the same approach without problem....

I glued my base plate to the floor to avoid any piercing of the concrete... I suppose if you pierced your poly barrier with nails, moisture could get to the wood- but in how many years? I've seen many basement remodels that were done before w/t wood was common and their walls don't seem to be rotting away...
Old 05-02-03, 03:00 PM
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Thanks for your input!
Old 05-02-03, 03:36 PM
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Ualdriver: I would just leave it as you have it. If you were going to start from scratch that is something different. If in the future at some time you do get one area rotting out (several years at least) then just replace that section. Good Luck

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