How to Level a Subfloor

No matter what kind of flooring you’re installing, it’s important to make sure the surface beneath it is level, smooth and flat.

Most subfloors — whether they’re a concrete slab or wood — will have low spots that require filling with floor patching compound.

Watch the video above to learn about leveling the subfloor. 

After the floor patch compound hardens, hire the pros to sand the subfloor until it’s smooth. Then you can install the new tile floors.


  1. I have a question. I have a woodfloors, the house is old and the room I want to put ceramic tile in is very un level. One corner of the room is approximently 3 inches higer than the other side. If you rool a ball it will go to one corner of the room. I would like to know if you can lay concrete on top of this floor? I am thinking of useing black paper with chicken wire and then put concrete on top. So one corner may have about 1 1/2 inches of concrete and the other about 3 1/2 inches. Also if this idea of mind is ok, then how long must I wait before laying the tile? The room size is 20 feet x 12 feet. I would appreciate your advice. Kathrin

  2. I just brought a new house with a unfinshed walkout basement with a roughed in unfinished bathroom in southern Missouri. I’m in getting ready to start the wall framing. How can I insulate a basement floor so as not have a cold floor in the fall and winter. And should I do that first before putting up the wall framing? I would like finish with carpet don’t know where to start on the floor. Also can I finish the basement bath with a subfloor or just bring the cement up to the sub-floor level to keep the floors even and level? Ricardo

  3. I have an enclosed front sun porch on an 85-year-old home with an slightly uneven floor covered with a faux brick linoleum sheet floor with asbestos matting underneath. Contractors have said we need to pour cement into the porch foundation to the tune of $15,000 to level the floor and then remove the asbestos, etc. before laying a new floor. All I want to do is lay down some ceramic tile (which I will have to do over the linoleum so I don’t have to remove the asbestos). I just want to lay down some plywood and backer board and then tile over that. Will that work? Any other suggestions?? Thanks a lot! Bill

  4. I have a small business, sealing and cleaning new and restoring old vinyl and linoleum floors.We recently found that after sealing a linoleum floor, swirl marks on the surface of the floor. My husband is adamant that this is because the substrate or subfloor was not dead-level when the floor was laid.I tend to agree with him as he has over 40 years experience in the use of sealants to seal floors. According to the client the substrate is epoxy that has been diamond-ground to a smooth surface. I think that the client is not
    truthful because the difference in price of an epoxy floor and linoleum is too large.Why would you install an expensive epoxy floor and then cover it with a much cheaper linoleum floor? Your comments will be appreciated?

  5. How can I remove black glue that was used in the 50’s to glue tile down? I used acetone on my basement floor and picked it up with kitty litter and that worked well but it isn’t working on my breezeway floor. Any suggestions?

  6. When I purchase 5 gallons of joint compound, I have problems with black mold growing on the top of the unused portion when I open the container the next time I need some. I never put any unused portion from a job or add water to the original container. I also put the plastic sheet back over the top. I end up having to throw the compound out as I can’t imagine it would be good to use moldy compound.

    • Hi Helen,
      I’ve had that happen to, and have had to throw it out. The only solution I know is to try to buy what you need for the job, and keep any leftovers in a cool place like a basement.

  7. We tiled out kitchen floor 8 years ago. We are now redoing our cabinets. Once removed, the subfloor is lower than the tile floor with backer board and there is a space about 1/2″ under the backerboard resulting in3 tiles cracking when stepped on.
    What is the best material to add under the edge of the backerboard prior to installing the new cabinets?

  8. Helen, that black glue is a real mess! When I redid my kitchen, I tried various types of scrapers and solvents to remove the glue without harming the oak hardwood flooring underneath it. I ended up scraping it off by hand with a razor blade, inch by inch. Some areas chipped off much easier than others, and once it was down to just grayish smears, I was able to get the rest off with a power sander.

  9. We have acid stained concrete floors and want to lay porcelain tile now. What is the least messiest procedures of preparing the floor? Do I need to put plywood down and then a backerboard of some sort? I would really like the least amount of mess and dust because of allergies if possible. Thanks!

  10. My house was built 1964 or 1970. The kitchen floor has press wood looking boards on the floor.Once I took up old tiles it look push up. In some places of the board. It still have old black glue on it. Some said put concret slab down or mic board. I not trying to send a lot of money and I am doing it myself. What happens if I put down the tiles. I lived there for 30 years. I want to get it ready before the winter

  11. If I am using backer board is it necessary to level the floor
    How much of a difference in height can a tile floor tolerate.

  12. We are retiling a bathroom in a 50’s ranch. The old tile and cement backing is removed and the 1 x 8 boards over joists are exposed. What is the best subfloor to put over these old boards before using Hardiboard, thinset, and tiling?

  13. I need to level my kitchen floor for new vinyl. There are places that are off about 3/8 in. what is the best way to level this out with a wood sub floor

  14. I bought a house that was built in 1924 over a pier and beam crawl space. The floor has been settling over the years to differences of 5″ in some areas. I already paid a foundation contractor to install smart jacks and try to lift certain sections but we weren’t able to lift more than a 1/2″ to 1″ at best. If the gaps are this big, it seems that buying enough concrete self-leveler will be cost prohibitive. Also, trying to remove the existing subfloor proved a challenge as it appears that there are several layers of subfloor that were added over the years so removing all of those layers is quite a bit of work as well. Should we add another layer of plywood with shims on top of the current subfloor to level it? Also not a cheap option but seems like our best option at this point

  15. We bought a brand new home, with travetine flooring. After a year, the travertine flooring start cracking on some sections. The contractor was saying, travertine flooring are soft, that’s why it’s cracking. The contractor wants to remove the entire floor and replace with engineered wood. Our suspicion the subfloor were not framed and secured properly. What’s the best solution. The house has a raised floor, we do have a crawl space.

    • Hi, Dee,
      Travertine flooring is porous, so if it was not sealed correctly, problems could arise. Of course, the subfloor also could have problems. Since numerous factors could apply, we recommend getting an in-home consultation.
      Thanks for your question!


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