Need information on putting wood floor over concrete.

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We are just getting ready to put a floor in our (to-be) dining room. We want to put down a wood plank floor over the concrete. I read somewhere that there are strips that must be put down first, but I don't know what they are called. We are going the "cheap" route and just using varying-width boards that have been tongue and grooved over an underlayment of particle board.. We will stain lightly, polyurethane like mad...and shoudl have a beautiful floor that will certainly outlast us. any ideas or suggestions are welcome, however, as we have been known to change our minds when given a better idea.

-- Wayne in Kentucky (wallen328@aol.com), February 12, 2001

Answers

The first thing I would want to know is how level is the concrete? I would start by laying out a plastic vapor barrier and then build a frame of 2x2's just like floor joists. If the floor has irregularities, you will need to place shims under the 2x2's to make the whole thing level. Then just lay your wood floor on that like you would on regular joists. One concern I might have is with the floor "bouncing" with only 2x2's for rigidity. One thought is to glue them to the concrete with an industrial adhesive and then laying the vapor barrier over that before your wood flooring. That should lock everything down and will give you a space of air for insulation. Depending on your climate and how cold the concrete might get, you could lay sheets of rigid foam insulation between the 2x2's.

-- Skip Walton (sundaycreek@gnrac.net), February 12, 2001.

Wayne: Why not thoroseal the concrete 2 times, Lay down a thick coat of U.G.L. top it off with thick plastic then lay down 2 by 6 tongue and groove planks? Thats what I did but I poured the concrete with nailers. Your concrete have wood nailers? Then I belt sanded and just finished it plain. here's a bad picture but you can get an idea. Kirk........http://www.geocities.com/PicketFence/Garden/8784/Int3.jpg

-- Kirk Davis (kirkay@yahoo.com), February 12, 2001.

We put wood parkay flooring down in my wifes sewing/library room. Waited untill the floor was cured properly sealed as per directions, did everything as we should according to the manufacturer and it was a nightmare. The factory man came out and looked at it and said some times it just don't work on concrete. Sometimes you will have a moisture problem that just should not be happening. The floor should have no problem but after this no more wood over concrete. Just our experience but be sure to look at everything before proceeding.

-- David (bluewaterfarm@mindspring.com), February 13, 2001.

Wayne, I think before you lay down your wood plank floor it would be best to put underlayment down over the concrete. This will give you a smooth surface to work from and also act as insulation between the concrete and your new floor.

-- hillbilly (internethillbilly@hotmail.com), February 13, 2001.

Wayne, the strips that you refered to are called sleepers. If it were me, I would lay 2"x 4" sleepers @16" O.C. There are screws that screw into concrete. They are called Tapcon screws. They come in lengths from 1" to 4". I would use 3" to screw down the sleepers flat on the concrete. With the Tapcon screws , you have to have a masonry bit to match the perticular diameter of the screws you use.Hope this helps.

-- Rick (rjconstruction1@excite.com), February 13, 2001.


Wayne: It may be wise to seal the concrete even if you use the sleepers. A friend put the sleepers down without sealing the concrete and the moisture still rotted his floor. Also make sure the ceiling is not to low if you go 4 inches more to the floor.....Kirk

-- Kirk Davis (kirkay@yahoo.com), February 13, 2001.

Wayne, let me start by saying good luck. none of this is meant to discourage you but these types of floors can be a nightmare. Do everything you can now to prevent future disaster. 1.) seal , seal and more seal on that concrete. Sealer is THE cheapest way to deter moisture and $ spent on it now will undoubtedly pay for itself. 2.) vapor barrier MUST be laid before any lumber of any kind!!! 3.) sleepers should be FIRMLY attached to concrete and Tapcons plus adhesive is not a bad idea. 4.) LEVEL LEVEL LEVEL, this will save you much aggravation both during install and after. You don't want to have to redo any of this work. 5.)You did not mention anywhere the thickness of stock to be used. It has been my experience that floors of less than 1" thick give unsatisfactory results eventually.So if your stock is 3/4" add a 1/4" underlay etc.etc., but build it to total an inch. 6.) you also didn't mention if this concrete is a floating slab or not. If it is you will NOT want to attach your perimeter sleepers to tha walls in any way as the wood floor must "float" with it. 7.) Best of luck!!

-- dan (dcbaker@2ki.net), February 14, 2001.

As for moisture barrier, if you want find if you have a moisture problemm, lay down a plastic cover on your concrete for 24 hrs. If, after 24 hrs. , the floor looks wet ,then you have a moisture problem.

What we normally do for moisture problem , is to apply asphalt foundation coatingwith a roller, with 30# felt overlay.

In extreme cases we have applied moistured displacing automotive body undercoating to concrete prior to moisture barrier.

Where is Wayne, need more info to advise.

\ Rick

-- Rick (rjconstruction1@excite.com), February 14, 2001.


I've also seen a rubber membrane that rolls out in sheets that they use on flat roofs. Anyone see why that wouldn't seal a concrete slab? ...Kirk

-- Kirk Davis (kirkay@yahoo.com), February 14, 2001.

Hi Rick,

I am in Kentucky. I plan on putting plastic over the floor first to check for moisture prob. thanks to all for the info on sealing, as I probably wouldn't have without the inputs. I love this web site!!

-- Wayne in Kentucky (wallen328@aol.com), February 15, 2001.



Wayne, hello , and hope you have great sucess with this project. Is this slab on the same level as the grade outside of your house , or is it inside a foundation that has been filled?

-- Rick (rjconstruction1@excite.com), February 15, 2001.

Hi Rick, The floor sits about 5 inches above grade. It is a poured slab floor. I currently have put mexican tile in the kitchen, and ceramic tile in the bathroom, and haven't had any moisture problems with them. I want to be sure that the floor is nice and dry in the, to be , dining room area before I put the wooden floor down. Lots of good suggestions from the folks here.

-- Wayne in Kentucky (wallen328@aol.com), February 15, 2001.

Wayne , if your floor is that close to grade , the you probably should put down moisture barrier.

-- Rick (rjconstruction1@excite.com), February 16, 2001.

The installation of wood to concrete should be done with a barrier over the concrete. This is usually 30# roofing felts. Then place the sleepers which should be 2x4's treated @1'-4" oc and anchor to concrete utlizing either stainless steel anchors and/or a zinc coated fastener. But one must review the slab condition for evidence of moisture problems. Has moisture been a problem in the past? The flooring should be installed leaving a gap @ the perimeter (walls) to allow for normal expansion and contractions due to humidity cycles. This also allows for air circulation to occur from belowthe finsihed wood floor. A wood base is installed over this gap to wall. Gap to wall should be minimum 3/8".

I hope this aids you in your project.

Rutter Architect

-- William Rutter (wrutter@uniontel.net), July 07, 2001.


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