Sometimes a concrete floor will begin to slope or sag over time. Routine wear and tear, poor installation or even nature itself can cause your floor to sag or slope. It may be that there are pits or valleys in your floor, or that one side is simply higher than another. Thankfully, you can fix this problem with the right knowledge and tools. Note that the procedure in this article addresses levelling a slope and not any underlying problem that may have caused the floor to slope.
Clean the surface of the concrete. Start by sweeping away any particulate matter, then give it a thorough scrub with the all-purpose cleaning agent and the scrub brush. This will ensure that all dirt, dust and grime that would prevent the bonding agent from working properly is removed.
Secure wooden dams at any openings on the perimeter of the room, such as doorways or hallways. These dams ensure that the concrete poured into the room stay within the room, so they must be taller than the intended pour height (in this case, taller than the highest point of the sloping concrete floor).
Obtain the dimensions of the floor--length, width and depth. The square footage of the floor determines how much of the bonding adhesive is needed, and the volume of the slope helps in deciding how much concrete mix is needed to create a level surface.
Follow the dilution instructions for the concrete bonding solution, using water and the small mixing container to make a batch. Apply the solution evenly to the concrete surface. The product instructions vary from brand to brand, so follow them carefully.
Mix the self-levelling concrete powder into the 5-gallon container filled with water. Directions on the powder package should detail specific ratios and mixing instructions so that you can determine the precise amount of mix you need based on the dimensions of your intended repair area. For example, a 22.7kg. bag may yield 25 square feet of coverage at a depth of 1/4 inch.
Pour the mixed concrete solution onto the sloped floor area. Start at the bottom of the slope, and work your way toward the top. Depending on the severity of the slope and total depth of the floor at the lowest point, multiple layers of concrete and bonding agent may be required. The self-levelling re-surfacer's package should have information on how deep each layer should be and instructions on how to properly pour layers into the area.
Allow the concrete to set for the time specified on the concrete package and remove the wooden dams.
Manufacturers' instructions vary, and it is important to follow these closely to ensure the end result is smooth and crack-free.