Patch and Level a Concrete Subfloor

We are well on our way to putting Humpty Dumpty back together when it comes to our mudroom and laundry room. The kitchen, it’s still a blank canvas.

After the water leak, the linoleum flooring had to be removed. What was left was a plethora of problem areas. Cracks, crumbled concrete and an uneven surface resembling the moon.

Patch and Level a Concrete Subfloor

Before putting down any new flooring, we had to have a smooth and level surface. Adding a self leveler was the best answer to the problem. We purchased most of the supplies from Lowe’s and borrowed a large drill. And here’s how we did it:

Patch and Level a Concrete Subfloor Materials:

  • Mapei Ultraplan (Self Leveler)
  • Mapei Primer T
  • Flat Trowel
  • 5 Gallon bucket
  • 4′ x 8′ Foam insulation sheet
  • Utility knife
  • Painter’s Tape
  • Paint roller
  • Paint tray
  • Quart measuring cup
  • Warm water
  • Drill with a large chuck and attachable second handle
  • Concrete mixing paddle
  • Concrete patch (if you have a crack)
  • Knee pads

Patch and Level a Concrete Subfloor

The picture above shows two drills. The smaller one won’t accept the mixing paddle. You need a drill with a larger opening. And, adding a handle to the side will help mix the heavy self leveler without it taking you for a “spin”.

Patch and Level a Concrete Subfloor Preparing the concrete floor:

Before pouring the self leveler there is some prep work required.

First remove any loose and chipping concrete. I used a scraper and lightly hammered any spots that sounded hollow underneath to loosen any weak pieces.

It is recommended that you rough up the concrete. I skipped this step because our subfloor was far from smooth.

Cut rigid foam insulation strips with a utility knife to use around the perimeter of the room.

Patch and Level a Concrete Subfloor

The insulation serves two purposes. 1. To create an expansion joint as the leveler expands and contracts with heat and cold.  2. And to prevent the self leveler from running into any cracks or through doorways. Plus, it created a nice channel to run some wires inside (more about that later in the week.)

Patch and Level a Concrete Subfloor

Use painter’s tape to secure the insulation around the perimeter of the room.

Patch and Level a Concrete Subfloor

Speaking of cracks, be sure to seal any large cracks with concrete filler and sealer. I neglected to fill this crack in the floor and literally poured 2.5 gallons of leveler into it before creating a little dam to stop all the leveler from pouring into the hole. Learn from my mistake, be sure to seal any large cracks in the concrete, or you’ll be doing the job twice.

Patch and Level a Concrete Subfloor

Let the concrete filler dry before continuing.

Patch and Level a Concrete Subfloor

Apply a primer to help the leveling material adhere to the concrete subfloor. Pour a small amount of primer into a paint tray.

Patch and Level a Concrete Subfloor

Using a paint roller, roll the primer onto the floor and wait for the primer to dry per the instructions on the bottle.

Patch and Level a Concrete Subfloor

The dried primer is tacky to the touch. If you wait more than 24 hours it will be necessary to reapply the primer.

 

Pouring and spreading the self leveling liquid:

Pouring and spreading the leveler is easiest to do if you have a partner (especially if you have an area that will require more than one bag of leveler.) One person can mix the next batch while the other is pouring and spreading. It is important to work into the wet edge or you will create ridges and bumps.

Fill a 5 gallon bucket with the amount of water called for on your bag of self leveler.

Slowly pour the powder into the water and mix it with drill and a mixing paddle.

Patch and Level a Concrete Subfloor

The mix will be soupy like tomato soup when it is properly mixed. But, it will be much heavier!

When the bag is empty and the mix is completely mixed. Let it sit for 2-3 minutes. Then mix it again and begin your pour.

Patch and Level a Concrete Subfloor

Immediately pour the liquid in 4′ sections and trowel it out, pushing more leveler toward any low spots.

Self leveler will do as it says, it will self level. But, only to a certain extent. Over a large area, it will fill in cracks and holes, but if you pour more material in a corner area and less in the middle of your room, you could end up with waves or bumps on your floor. Try to pour a consistent amount in each area.

Patch and Level a Concrete Subfloor

Work into the wet pour with your next batch until you have finished leveling your area. Let the leveling liquid dry overnight before walking on it. The self leveling liquid will dry lighter and to a matte finish.

Patch and Level a Concrete Subfloor

Clean out your bucket and trowel with LOTS of water. Hopefully you won’t have much leveler to dispose of. If you do, let it harden in a container you don’t mind throwing away.

Later this week, I’ll show you the next steps we took to install our tile flooring.

Patch and Level a Concrete Subfloor

 

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How to Patch and Level a Concrete Subfloor | Pretty Handy Girl

35 replies
  1. Kendra Jones
    Kendra Jones says:

    Brittany,
    Do you think a color can be added to the leveler mix. I was wondering about saving a step for the staining. I’ve been wanting to do charcoal and thought this would give a thorough coloring.

    Reply
  2. Tim
    Tim says:

    Hello and good job on a quick fix! I’m looking to do a similar process to a 1200 sq. house. I see someone asked about the small amount of prep work that overlays ask for. Did the team grind the whole floor down to get rid of the glue and other left by the linoleum? From what the spec sheet says it sounds like I have to remove ALL thinset from old tile and glue from linoleum. Is that too much prep considering we have to use a primer? Thank you

    Reply
    • Brittany Bailey
      Brittany Bailey says:

      Tim, I don’t think they did grind it down. I did vacuum it up the best I could. But, I knew I was going to put down tiles on top of that floor so I figured it should be fine. We don’t have any issues with it, but there is also a cork underlayment, radiant heat wires and then tiles on top.

      Reply
  3. Debra Johnson
    Debra Johnson says:

    Hi , Brittney:
    Thanks for this tutorial. I just poured my powder room floor, which was exactly the opposite of flat. It looks pretty flat now, though. Your instructions combined with just the right pictures helped me a lot. Much appreciated.

    Reply
  4. Dan Narozny
    Dan Narozny says:

    Good advice except when done mixing do not let mix sit. Pour immediately. Drywall mud and such needs to sit and mix a bit more. Not self leveling underlayment as used in above article.

    Reply
  5. Bauer Hardwood Flooring
    Bauer Hardwood Flooring says:

    This is a great article but it seems to be missing something. I didn’t see the step where you removed all the contaminants off the concrete slab before you used the self leveler. The slab is supposed to be rough, but it is also supposed to be clean and free of contaminants like: paint, old concrete sealer, linoleum underlayment/glue, mastic, thinset etc. Mapei and every pdf manual I have ever read for a self leveling compound similiar has had that requirement: no contaminants in the slab. Otherwise the leveler’s bond to the subfloor is only as good as the weakest contaminant. The rigid foam looks like the handy idea, I will check it out.

    Reply
  6. Mary-Beth Patterson
    Mary-Beth Patterson says:

    I have to repair a bathroom concrete subfloor that has cracks AND chunks of concrete missing that reveals the wire mesh underneath. Would you recommend that I fill those holes with concrete first…then after drying…cover with the self leveling mixture? Concerned that the 2-3 in. deep holes will take too long to dry and needs to be strong enough. Any suggestions?

    Reply
    • Brittany Bailey
      Brittany Bailey says:

      Mary-Beth, that does sound like a good plan. 2-3 inches is VERY deep. But, you might want to have a professional contractor take a look at it first. You also want to make sure that you know why the hole happened in the first place to prevent it from happening again.

      Reply
  7. Dale Roach
    Dale Roach says:

    I am impressed with everything you have posted about this! I plan on installing glue down Bamboo flooring after following your lead. Can I leave the insulation in place to act as a spacer shim to do this? Please enlighten me!

    Reply
    • Brittany Bailey
      Brittany Bailey says:

      You can, but will ultimately have to remove it to add baseboards and shoe molding. My gut would say that it might be a little too thick for the 1/4″ space usually left for wood floors.

      Reply
      • Shannon
        Shannon says:

        Can you talk a little bit more about removing the insulation? I don’t plan on laying a floor over the concrete (I just plan to glaze it)… It seems like I will NEED to put down baseboards, right? Or else what does the edge look like??

      • Brittany Bailey
        Brittany Bailey says:

        Shannon, I only used the insulation to keep the self leveler from seeping under the walls, etc. If you are just skim coating, you probably don’t need it. UNLESS, your floor isn’t level and the liquid pools to one wall. Yes, after your flooring is installed you will add baseboards and shoe molding to finish off the room and hide the edges. Make sense?

      • Shannon
        Shannon says:

        OK yes, I think this makes sense. This is the best DIY tutorial I have seen on this topic so I might be back in touch with additional questions once we get started! Thanks so much!!

      • Shannon
        Shannon says:

        Ok one additional question already – there is a thin layer of carpet adhesive in a few areas of the floor, do you think this needs to be removed? Or can we just lay the self leveler overtop?

      • Brittany Bailey
        Brittany Bailey says:

        I’d remove it as best I could. Whether you have to scrape or use a paint thinner. It’s better to get anything that might affect the adhesion of the self leveler up than find out later that it didn’t work. And then you’d have it flaking up and pocking. Especially because it sounds like you aren’t using it very thick. And be sure to use the primer ahead of time.

      • Steve
        Steve says:

        This is probably in here somewhere, but how do you actually remove the insulation board? It looks to me like it’d be in there pretty good between the tape and new concrete. Does it just pull straight out, or do you have to cut it or scrape it, or…???

  8. Maude
    Maude says:

    Congrats to you for your success. I have a basement bathroom and I ended up hiring a tile man to do the job. Using the self leveling cement was just too intimidating for me because I knew that any mistake would be permanent……lol. You make it look so easy!!

    Reply
  9. Suzy @ Worthing Court
    Suzy @ Worthing Court says:

    I’m so glad you posted this, Brittany! We have a bathroom in our basement that my hubby used self-leveler on before he applied vinyl flooring. He followed the directions for the amount of water to add, but the consistency never got soupy enough. Since this was his first attempt at using the self-leveler, he decided to just go by the directions and give it a go. It turned out terrible. Now we have to rip up the flooring that is there and re-do the whole thing. Ugh. This time, we plan to lay tile though. 🙂

    Reply
      • Randy
        Randy says:

        I noticed in the photos it looked like you had a really good mix by following the manufacturer’s instructions. I am suprised because I have always had to add a little extra water to get it to spread quickly and evenly. May I ask what brand you were using? 🙂

  10. Ben Gareen
    Ben Gareen says:

    Great How-to article. I’m thinking of attempting to level a whole room by myself. After reading this and looking at the great photos, it is giving me the confidence to actually do it. Thanks Britany! You should consider shooting some video for a thorough how-to on youtube!

    Reply
    • Brittany (aka Pretty Handy Girl)
      Brittany (aka Pretty Handy Girl) says:

      Thanks Ben. Actually I did have someone shoot video, but my cameraman was too shaky. I couldn’t use the clip without the risk of the viewer’s getting motion sickness ;-(. I did see that the pros wear cleats so they can walk in the wet areas. And, if you are doing a whole room, maybe rent a small cement mixer? It might save your back and allow you to work into the wets areas.

      Reply
  11. Crystal
    Crystal says:

    Kuddos to you!! I’m so impressed!! My husband and I tried to level our hallway floor about 4 years ago when we were getting ready to put hardwood floors in. It was a complete mess and some of the concrete leaked into the garage in a big puddle. We both swore that day that we would never attempt to do that again. Great job!!

    Reply

Trackbacks & Pingbacks

  1. […] Before putting down any new flooring, we had to have a smooth and level surface.  See more […]

  2. […] After the mat and heating wire has been secured, run the excess ends of the wire at the base of your wall (the wire fits perfectly in the channels made with the foam insulation strips I used when pouring the self leveler.) […]

  3. […] up the thinset according to the package directions. (The process will be very similar to how we mixed the self leveler.) The thinset should have a very thick consistency that will hold it’s shape when glopped on […]

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