If you are installing new flooring in your home but are concerned about low spots or high spots in the concrete subflooring that don't match adjacent levels, then rest assured. You can easily correct these problems with a self-leveling concrete mix that will dry quickly and provide a smooth, level subfloor for your new flooring. Below is how you can do this job yourself:
Tools and materials needed
- Concrete resurfacing mix
- Concrete priming compound
- Paint roller holder and roller with low nap
- Five-gallon bucket
- Trisodium phosphate (TSP) powder
- Electric drill and mixing implement
- Rope caulk
- Torpedo level
- Two colors of chalk
1. Clean the subfloor to remove grease and dirt - for the resurfacer to adhere without cracking or spalling, the concrete subfloor must be free of grease and dirt. Mix together one-half cup of TSP powder with one gallon of hot water and apply the solution with a mop. After the subfloor dries, use a clean mop dampened in hot water only to remove the TSP residue from the concrete.
2. Prime the subfloor - once the subfloor has been thoroughly cleaned, then you will need to apply a concrete primer to give the surface better adhesion with the resurfacer. Mix the concrete primer of your choice according to the manufacturer's directions, and apply it in a thin coat using a paint roller with a low nap. Be sure to spread the primer so it doesn't clump or dry with ridges.
2. Locate the uneven areas - if you have difficulty knowing the specific locations of your lowest spots, use a torpedo level to find the areas that need building up. By moving the level around and orienting it in different directions, you will find the slopes and know where you should pour the resurfacer. Mark the low spots with a piece of colored chalk and also mark the highest areas with a piece of chalk in another color.
3. Create a containment area for the resurfacer - you may need to erect barriers to help control the flow of resurfacer if the slopes are too extreme or there are no natural barriers to keep the material contained. If so, then you can use rope caulk to form a low dam along the edges of areas that need to be protected. Rope caulk is easily placed and removed when no longer needed and is also ideal for inserting into gaps under studs or other areas where resurfacer can leak.
4. Mix the resurfacer - determine how much water needs to be added based upon the product directions and add a measured amount of water to a five-gallon bucket. Next, pour the powdered contents of the bag into the water, never the water into the powder, and mix it for several minutes using an electric drill and mixing implement. Be sure to continue mixing until the resurfacer is smooth and lump-free throughout.
5. Pour the resurfacer - after mixing, begin pouring small amounts of resurfacer into the low spots you marked in step 2; you can use a type of concrete pump to do this as well. Use a trowel to spread the mixture out, and continue adding more resurfacer and spreading. Do not add too much resurfacer at one time or you will likely end up with uneven areas.
6. Smooth the resurfacer - once all of the resurfacer is added, touch up any areas with your trowel that appear uneven. Don't continue to spread the resurfacer too far from its original location, however, and allow several minutes for the resurfacer to settle into place on its own. Allow the resurfacer to dry for the period of time instructed on the bag, and be sure to install an appropriate vapor barrier over the resurfaced subfloor to protect the new flooring from evaporating moisture.