There are many advantages to finishing the basement of your house. At the very least, it’ll up the value of your home and give you an edge on the market.
But what do you do if the floor isn’t quite even? An uneven floor causes a lot of problems, from framing to applying a finished floor. Starting a project, such as finishing your basement, with a good foundation is critical to keeping your sanity throughout the project.
Floor Leveling Options
How perfectly level the floor has to be depends on the finished product. Flooring options such as Carpet, engineered hardwood or click together vinyl are more forgiving and require less work. With these materials, a cement grinder and a bucket of mixed cement are all you’ll need. Use the grinder to grind down any high ridges and use the bucket of cement to fill in any dimples in the concrete. An absolutely smooth and level floor isn’t critical.
If your finished product is either tile or the concrete floor itself, the concrete will have to be more or less perfectly even and smooth. When installing compact tiles, the rule of thumb is 1/4″ differentiation from the highest point to the lowest point in a 10 square foot radius. If you’re installing the more conventional larger tiles (1×2 ft), the rule of thumb is 1/8” differentiation from the highest point to the lowest point in a 10 square foot radius.
There are many options when it comes to leveling a concrete floor, the most cost effective, however, is a self-leveling cement or compound. Keep in Mind DIY self-leveling of a floor is not for the inexperienced. There are many reasons why self-leveling a floor is not the easiest DIY job. Leveling a concrete floor takes lots of prep work and if not done right can be incredibly expensive to repair.
Prepping the Floor for Leveling
Having said that, if you are up for the challenge, the first thing you’ll have to do is prepare the floor for the concrete leveling compound. The first step is to remove any paint flakes or adhesive on the floor.
You want to minimize the amount of compound you have to use, to do that use a cement grinder and grind down any predominantly highly spots and use mixed cement to fill in any pits or holes. Once you’ve done all that, sweep up any debris then use a mild cleaner, such as dish soap or TSP (trisodium phosphate), in water with a soft bristle brush (a stable broom is perfect) and scrub the floor.
The last step to prep for the overlay is the make sure to seal around the seams of the drain (if there is one), and block with a piece of wood any opening to keep the compound in the enclosed area. Make sure to use tape to seal the wood so the compound can’t escape through any cracks in the wood. Once the floor is dry, you can start adding the concrete leveling compound.
Applying the Concrete Leveling Compound
To get the best results, brush a self-leveling concrete primer over the entire floor. This will assure that the compound sticks the old concrete surface.
There are a lot of concrete leveling compounds on the market, whichever overlay you choose to use make sure to read the manufactures instruction carefully. Mix a batch of the compound in a bucket. Remember to pour the dry concrete mix into the water and not the other way around to assure that the mix is properly made. Use a paddle mixer and make sure to get out any bumps out of the mix before proceeding.
Once you have the leveling compound mixed, pour the thin liquid, starting at one side of the room to the other, across the floor in narrow strips that overlap slightly and allow gravity to level to mixture. Generally you want a minimum of a ¼” over the entire floor. This will assure that all imperfections have been covered. If you want to speed the process up, you can use a broom or a trowel to gently move the liquid across the surface of the uneven concrete.
Make sure to plan how you want to pour the compound the assure you don’t get trapped in the room. It’s a good idea to wear a pair of cleats in case you have to walk across the cement compound while it’s still wet. Make sure to apply the mixture to the entire room at once as the compound will set quickly. It may be in your best interest to have someone help you to make sure that the job gets done in a timely manner. Once you’ve applied the compound to the old surface, let the new surface cure for about 48 hours.
Personally, we use concrete overlays to level a floor. A concrete overlay is a hybrid polymer resin based cement that can be a tricky and expensive product to work with. It takes lots of experience and knowledge to apply successfully. Even though it’s difficult to work with, the overlay is engineered modified polymer that, when it’s poured directly over the existing concrete or sub-floor, it clings to the surface and is considerably more flexible, thereby resulting in less or no cracking.
If you were planning on just having the concrete as your finished product, consider adding colour to the concrete mix to add a unique feel to the room.
Need some ideas? Or just want to get a better sense of whether concrete overlays might be the right solution for your uneven floor? Take a look at our more detailed article about concrete floor leveling and resurfacing.