Concrete floors can become unlevel or uneven for many reasons. You have two options when you need to level concrete, hire a concrete leveling professional or do it yourself.
If you plan to do it yourself, the first step taken to resolve any concrete floor issue prior to proceeding with any concrete floor repair needs to be an assessment of why the floor is not level or flat. While there are multiple makes of self-leveling cements and underlayment’s, such as CST Rapid Set, Ardex, Sika, Quickrete, Sakrete, and more, none of these products should be applied without proper information and research, or failure can occur.
Let us begin by addressing “level” and “flat.” Not all concrete floors are installed level. Floors such as garage floors and basements are typically poured with pitch to allow any water that gets onto the floor surface to drain, either out of the garage doors or into a basement sump pump. While not all floors are meant to be level, they should all be flat without significant dips or humps.
The following addresses the most common concrete floor issues:
Above Grade Floors –
- Above grade concrete floors such as garage floors, home floors, and commercial floor slabs can be subject to settlement when poured on loose backfill which tends to settle. Once this settlement occurs, a void can develop, leaving the concrete floor unsupported. The floor will then sag and become uneven. Prior to any concrete floor surface repair, these floors must be filled and supported by injecting a cement grout beneath the floor. Once the floor has been filled or raised when possible, it can then be assessed for a surface repair method. Keep in mind that garages are not typically heated in northern climates. Frost and ground expansion may cause slab movement. Cracks that are present in the floor are prone to reflect up through any topcoat material applied and product installation temperature ranges need to be read and followed closely.
Below Grade Concrete Floors –
Basement floors generally do not settle but are known to be poured unevenly with highs and lows due to limited access during the installation and finishing process. This is typically discovered when attempting to install a vinyl plank floor system or hardwood floors on top of the concrete floor and noticing the floor does not have a sufficiently flat surface.
Things to take into consideration that can affect adhesion and durability of topcoats –
Floor moisture issues
If surface failure is present, cause needs to be determined
Oil Stains, Paints, Glues, Or Other Bond Breakers
Improper mechanical preparation of the floor surface
Improper primer product selection
Improper selection of self-leveling cement product
Steps for proper assessment and application for leveling a concrete floor –
- Determine if there is a surface failure, or the concrete surface is solid. If there is deterioration, this can be due to an overwatering of the concrete, freezing temperatures, blowing heat onto the surface to accelerate setting, or a faulty concrete mix design. Placing a cement overlay on a dusting or deteriorating concrete surface will fail.
- Determine if floor moisture is present. This is not determined by visible moisture only. A moisture test is recommended to determine MVER, or Moisture Vapor Emissions Rate. A rate of three pounds per one thousand square foot or below is an acceptable rate. Kits are available for purchase online and the test takes 24 hours.
- Paints, glues, oils, and sealers will all function as bond breakers and prevent any self-leveling product from adhering to the floor surface. The products must be mechanically removed through metal shot blasting or grinding the floor surface to a proper surface profile.
- Based on the MVER test and moisture content, the next step is to determine the proper primer needed for bond and adhesion. For floors with normal moisture requirements, an acrylic based primer is typically used. When higher moisture levels are present, epoxy-based primers with a sand broadcast are recommended, however, they are more costly and labor intensive to install.
- Selecting the proper floor underlayment or overlayment product is necessary. An underlayment is to level the floor surface and install a floor system over. It is not made to be the final wear surface. An overlayment once installed can be used as the final floor surface. Also, moisture needs to be considered when selecting the proper product.
Self-leveling Cement Application Steps –
- Mechanically prepare the floor by shot blasting or grinding the surface. Check with local rental yards for equipment availability
- Vacuum and clean the concrete floor well. Apply proper primer for your application and honor recommended application times of self-levelers.
- Seal off any areas or gaps around the floor perimeter or holes in which the self-leveler can escape. Pin any deep areas with tapcons to grip topcoat.
- FIRST READ ALL PRODUCT INSTRUCTIONS. Mechanically mix the self-leveling product. A proper sized mixing drill and mixing paddles designed for mixing self-leveling cements should be used. There are mixing drums with handles sold on the market for this purpose. Depending on the floor area to be covered, two drums may be necessary. Have enough help on hand to mix continuously. I recommend two persons per drum. Pay special attention to the percentage of water recommend by the manufacturer as overwatering the product will reduce its strength, while underwater will reduce its flow and workability.
- Begin applying self-leveling cement from one end the room, working backward toward your exit point with a gauge rake and smoothing trowel. Spike shoes should be worn so you can walk into the self-leveling product to spread and level.
Once cement set time is complete according to the manufacturer’s specifications, your floor is ready for use or to install your new floor system.
Of course rather than doing it yourself you can hire a professional concrete leveling company like Concrete Chiropractor. Contact Us for more information and a quote.