Need some advice to install a plywood floor over concrete please.

Question

I have been researching a lot and would like to install a plywood floor over concrete in two bedrooms in our basement. I have seen many blogs and read a lot, and know it can be done, but, need a bit of help. I have read in some places that you NEED a vapour barrier to put over the concrete before installing the plywood and in other places to just glue the plywood to the concrete floor. We have been in our house for 5 years now and haven't got any moisture in the basement, and there has definitely been opportunity. This plywood floor would be the floor, not a subfloor. I have read about nailing it to the concrete, but that could wreck the look of the plywood, do I think gluing is the best, but, can I just glue straight to the concrete or if I out a vapour barrier, glue it to that? My concern with gluing it directly to the vapour barrier, is, do I need to attach the vapour barrier to the concrete somehow? And if not, will it all shift? I hope this all makes sense. Thanks for any help and advice anyone can give!

Lorraine Chipman · Answer

Don't glue the plywood to the concrete. Concrete has moisture in it and your wood will mold and rot over time. There is a product you can buy from your local home depot store for putting under a floor over concrete. It looks like a sheet of dimples or very large bubble wrap. I don't remember what it is called but it comes in a roll 6 ft by 50 ft. You roll it out and just lay your plywood right on top and fasten it down. It lets the natural effervecense ( leeching water ) evaporate and the floor to breath. This also helps keep the floor dry and warm. If there is ever a leak the water just runs between the dimples. It will add about 1/2 an inch to the height of your floor.

Rachelle Morris · Answer

@Lorraine Chipman I will look into that! Thanks. 
@Larissa ~ Prodigal Pieces I want the plywood to be it- the final surface. I have read a number of blogs that say they put it over concrete without a sub floor, yet didn't say exactly what they did. Thanks!

Rachelle Morris · Answer

Yes, makes sense. I have read so many different things. hahaha... I think I will go back and see if I can find out more info. ... I find with most blogs, getting answers to questions is useless, but I will try. Thanks. :)

Spheramid Enterprises · Answer

What you need to do is find out IF you need a vap. barrier FIRST. Tape a clear sheet of plastic wrap about a foot sq. down for a day or so and see if it gets condensation under it.. Yes? needs a floating floor, no? Bostic's Best glue and a notched trowel for any type of wood.

Lorraine Chipman · Answer

@ Rachelle where in Canada do you live? I live in Southwestern Ontario. The product I mentioned is called Dimpled Membrane. It will act as a vapuor barrier for your floor. It is origionally meant for basement walls. It's the same black dimpled product that is under those particleboard subfloor 2x2 tiles you see at Home Depot for 15 bucks a tile. You fasten it to the floor with concrete screws through some dimples. You put your floating floor on top. If your floor is plywood you don't need anything else. It will also help if you have any small humps and roughspots in your floor that potentially give you uneven joints when you butt your plywood together. The air spaces between the dimples also act as insulation and keeps your floor warmer than if your floor was laid on bare concrete. It doesn't matter where you live, concrete is damp. That's why it is so cool. Google dimpled membrane. (Also if you use tongue and groove plywood you can glue the peices together and not worry about fasteners.)

KMS Woodworks · Answer

I did one a few years back where I installed 2 x 4's on the 'flat' and filled the spaces with blue rigid foam, then the ply was installed and then hardwood. Insulated, warm and quiet.

Rachelle Morris · Answer

thanks everyone! @Scheramid Enterprises I will do that for sure. I read somewhere else that I may not need a vapour barrier because there should be one under the concrete already.... but I don't know that for sure.
@Lorraine Chipman I live in Edmonton, Alberta. I will check into that dimpled membrane! Thanks for the name!
@KMS Woodworks thanks for all the details. I was hoping to keep this very simple and cheap too. I haven't done anything like this before, so don't want to get in over my head... although I think I already may be...
I did find a flooring business very close to where I live, so I think I am going to go in there and talk to someone there and see what they have to say too. Thanks again everyone!

Woodbridge Environmental Tiptophouse.com · Answer

I would stay away from any wood floor over cement if its below grade. Even the dimpled blocks sold at the the big box stores. As someone who does a lot of mold removal, I can tell you they do not work, and any trapped moisture below the surface even if plastic is involved you will end up with rot, insects and mold not to mention odors. 
I would suggest that you use a hard tile on the floor followed by a removable area rug that can be taken up from time to time to have professionally cleaned. If you like the tile look, then you can have heat tapes installed under the areas in which your feet will be located. So the tile will be warm to the touch. 
Purchase a book called 'My House Is Killing Me' written by Jeffery May. After reading this you will have another entirely different approach to covering you floors in wood.

Rachelle Morris · Answer

thank you so much. I have heard of that book and will look into it. Thanks so much!

Rachelle Morris · Answer

I will have to go in to a store about the tape. I looked a bit online and found matts, etc. but they are very expensive and then one has to buy the thermostats with them and install them.... yikes. That is definitely more than what I was thinking. My hisband's cousin just called tonight telling us about those blocks you were along about and telling us those are the best; he has worked with them before. Oh my..... this is so much more difficult than I thought! Every time I talk to someone, I change my mind again because someone else makes a great point.... not sure what we will end up doing...

The Garden Frog with C Renee · Answer

How old is the home? Was the basement to finished later on when they built the home? 
Do you have any odor~musty or stale smells in the basement? do you want wood, tile or carpet?
I agree with Woodbridge Env if the home is older and the basement was not built to be finished (does that make sense?) If the basement was meant to be finished, then I would do the moisture tests and move forward. I have had in a previous home with a basement carpet installed with a special pad for vapor barrier. in 5 years never had any issues. There are always going to be 'what ifs' and 'this could happen' which makes a decision such as this very hard. Plus, are there egress windows if you are going to make the rooms bedrooms? that is important information to determine budget for your flooring as well. More and more points to consider when renovating or replacing~that is what owning a home is all about~spending time and money to make it yours.

Rachelle Morris · Answer

I think the house is about 40yrs. old now and the basement is a finished basement. It is half in the ground, half out.... the windows are about half the wall in the rooms. (Sorry, not sure what that is called.) we haven't had any issues with moisture or odours due to moisture. We have lived here 5 years now and if we were going to get moisture, actually flood waters in there, we would have got me. We have had more than a few opportunities for that. :) the rooms we are doing are bedrooms already. We had to rip out really gross carpet in the two rooms when we moved in and put new stuff in. Those are the only two rooms that have carpet in our whole house. I hate the carpet for two reasons.... it is just gross. It just cannot be cleaned properly and with kids in those rooms all the time, they aren't kept cleaned properly. With anything else, they can sweep and wash. We did do the vinyl tile in the areas all outside those rooms and the bathroom down there. We are thinking that again, but it is very cold. I am looking into the heated floor, but wow! that looks like it could be quite the project and money... However, we will be putting area rugs in there anyhow... I will do that moisture test and see what comes of that. Thanks again! I do appreciate all the advice!

Phil Miller · Answer

A floating wood floor is good. No glue, just tongue & grove the edge so that the plywood is joined to something. Tongue and grove the ends also.

Charles Smith · Answer

Do a floating suspended floor. First, put down 6 mil plastic. Then buy 3x3x0.75' foam blocks and glue them to a 1/2' thick plywood (50 per 4x8 sheet). Lay as many of these sheets as you need on the concrete to make the first layer of subfloor. Then put another layer of 1/2' ply over top of the first layer, but at a 90 degree angle. Try to make it so no seams overlap. THEN put your floating floor on top of that. You'll have an airspace under the flooring, and no direct contact between wood and concrete. This is how dance floors are constructed, by the way. It will be a LOT more pleasant to walk on than a wood floor applied directly to concrete.

Marion Nesbitt · Answer

You can also check Rescon Basement Solutions.

Devin Henderson · Answer

Hi, 
I was wondering did you ever figure out how you would go about installing the plywood? I'm looking into starting this project next year and was wondering the same thing in terms of letting it be a floating floor or sticking the moisture barrier to the floor and/or gluing the plywood to the moisture barrier. Our home is only 4 years old with concrete sub-floors. Any insight on your findings would be helpful.

Thanks in Advance

Rescon Basement Solutions · Answer

Thanks Marion! I wanted to add the following about adding flooring over concrete slab in the basement. While problems may not occur for some folks, the chance is always there for things to go wrong. You may not have water that you can see but you could have moisture and water vapor regardless. Here is a bit of info. from our Blog that you may find useful: Water vapor occurs when hydrostatic pressure forces any water below the basement floor to vaporize. This vapor is then able to pass through the porous concrete. If any flooring is laid directly on the concrete floor, the moisture will become trapped and continue to accumulate over time. The build up of water vapor will cause problems such as mold and mildew. Also, if the flooring is carpet or manufactured from organic material, such as wood or laminate, not only will mold grow, but the floor will buckle and begin to lift and become unusable. I hope your project is working well! http://blog.resconsolutions.com/basement-flooring-flooring-in-a-finished-basement-can-be-stylish-and-comfortable-but-be-aware-of-two-variables/ Also, visit http://www.resconsolutions.com/our-solutions/Basement-Finishing/basement-flooring.aspx to read about suitable solutions.

Devin Henderson · Answer

Hi rescon basement what are your on adding plywood to concrete (not as a subfloor) if you dont have a basmentment?

Diane Kirsch · Answer

i want to do the same...lay down either real wood planks, or 'faux'...but, i am in a prefab on a slab...i worry about the vapor barrier...! I would think this would mold because it wouldnt be able to 'breathe'....am i worrying uneccessarily?

Lorraine Chipman · Answer

If you lay your floor directly onto cement it will absorb the cold and any moisture that wicks out of the cement. Concrete is porous so there is always moisture. Even if you are laying tile you should use a membrane. There is a product you can buy called DMX-1 Step from home depot. I'm sure Lowes sells a similar product. It goes betwen the concrete and plywood. It has large dimples on both sides so any moisture that wicks up through the concrete can evaporate. It also acts as insulation because there is now air between the cement and your floor. The good thing about this stuff is you don't have to lay a plywood subfloor if you are putting down a hard surface flooring like wood or laminate. It's alot less expensive than buying the prefabbed subfloor tiles and it comes in large rolls so you just roll it out.

FrugalMumma · Answer

We recently purchased a home. First thing I said to hubby was that the carpet and popcorn ceilings were going. They've gone... however... the whole basement cement floor has been painted... we also have in floor heating in that it was laid when the slab was poured. House is 18yrs old, no mold/mildew... I've seen lots of posts on pinterest about cutting wide planks with plywood and laying those onto the slab. So my question is a little different in that we have in floor heat and a painted cement slab... any ideas on whether I can just glue the plywood down. I'm not wanting to drill into the slab due to the inslab heating... gosh hope that makes sense... appreciate any insight. Oh, I'm in Calgary, Alberta.

Foy Walker · Answer

I need to rise the concrete floor hallway 5×8, to make it even to install laminate woof plank flooring. Do I need to attach the 1/8 plywood to the concrete before installing new flooring. Thks

Whi13352713 · Answer

Why has no one suggested using dryloc clear concrete sealer and then glue the plywood directly down using liquid nails or glue you use with toothed trile and then lay plywood down? You can even buy roll on flex seal (as seen on tv) or home depot has their own brand

MissAliCat · Answer

Hey smart people... why don't you actually read the dang question.

Basically, she is installing floating wood floor, so the wood floor does not go under the cabinets.

In order to raise the cabinets to match the floor better and so the dishwasher does not get trapped under the countertop.

She wants to put plywood UNDDERRR the cabinets to RAISE THEM HIGHER to match the wood floor height. NOT under the wood floor... or whatever insane thing you think she's asking.

SoOoOo... can someone answer the ACTUAL question please? No one has done too good of a job answering it yet, and I am having the EXACT same issue.

Joni · Answer

Rachelle, did you ever get to do this project? I have the same questions you did.

Joni · Answer

You sound so much like me! I researched painting my cabinets for years before I took the plunge. Sometimes it's just information overload. My husband calls it analysis paralysis. I will let you know if we do anything. My project list is so long today who knows lol.

Need some advice to install a plywood floor over concrete please.

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Need some advice to install a plywood floor over concrete please.

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