Uneven concrete floors can be an issue for homeowners, whether in basements, garages, or kitchens. Fortunately, leveling these floors is a project you can tackle yourself with the right tools and techniques. In the video, This Old House general contractor Tom Silva demonstrates how to use a self-leveling compound and rail system to create a smooth, even floor.
Self-Leveling Compound
Self-leveling compound, liquid floor underlayment, or floor resurfacer, flows like thick syrup and hardens into a level surface. This material minimizes headroom loss in lower spots on your floor.
Types of Self-Leveling Compound
The most common self-leveling compounds available are gypsum-based products, hybrid formulations, and Portland cement-based products. For basements, Portland cement-based products are recommended because of their moisture resistance.
Self-leveling compounds have many benefits, including adhesion to existing concrete, minimal shrinkage, and quick setting time, and they can be applied in thin layers for a more level finish.
How To Prepare the Concrete Floor
Before applying the compound, properly prepare the existing concrete floor for a successful DIY project.
Cleaning the Surface
Start by cleaning the floor. Dirt, dust, and grime left on the surface can interfere with the adhesion of the leveling compound, causing it to peel or separate over time.
- Remove any loose debris with a broom or vacuum.
- Use a degreaser to remove surface contaminants.
- Rinse the floor and allow it to dry completely.
Repairing Damage
If imperfections are left untreated, they can disrupt the evenness of the leveling compound, leading to a floor that might be uneven or prone to further damage. If the floor has significant cracks or damage:
- Clean out any loose material from cracks.
- Apply an appropriate patching compound.
- Allow repairs to cure before proceeding.
Setting Up the Rail System
The rail system serves as a guide for the self-leveling compound, helping to spread it evenly across the entire area. Without a rail system, it can be challenging to gauge the exact thickness of the leveling compound needed, leading to potential inconsistencies that can compromise the floor’s integrity and appearance.
Materials Needed
Gather the following materials from a local home improvement store:
- 2×4 wooden rails of appropriate length
- Circular saw
- Construction adhesive
- Hammer drill with carbide-tipped masonry bit
- Level
- Masonry nails
- Screed (6-inch-wide straight-edged board)
- Scribing tool
- Shims
Installing the First Rail
The first rail sets the foundation for the system:
- Position a straight 2×4 rail diagonally across the floor, with one end on the room’s high point.
- Use shims to level the rail as necessary.
- Match the bottom of your scribe tool to the floor surface and trace the contour onto the board.
- Cut the rail along the scribed line with a circular saw.
- Check the fit of the board in the same position where you scribed it.
- Secure the cut rail to the floor using construction adhesive and masonry nails.
Adding Subsequent Rails
Once the first rail is in place, add the others using a similar process:
- Place the second rail lengthwise across the floor, resting one end on the first rail.
- Shim, scribe, and cut the second rail as you did with the first.
- Repeat the process for any additional needed rails.
- Check for levelness multiple times during installation.
Applying the Self-Leveling Compound
With the rail system in place, you’re ready to apply the self-leveling compound. This step requires careful mixing and application for the best results.
Mixing the Compound
- Follow the manufacturer’s instructions for mixing ratios.
- Use a 1/2-inch drill fitted with a mixing paddle.
- Mix until the consistency resembles a thick batter.
Application Process
Work quickly through the following steps because the compound sets rapidly:
- Protect cabinets or appliances with padding if you are working around them.
- Pour the compound slowly inside the rail perimeter, slightly overfilling.
- Use a screed across the rails to level off the compound.
- Work in sections for even coverage before the compound begins to set.
Tools for Spreading the Compound
Use specific tools to spread the self-leveling compound and make the process more efficient. Apart from the screed, you can use gauge rakes and smoothing trowels. Gauge rakes help spread the compound evenly to prevent pooling, and trowels can smooth out the thin layers to produce a polished finish.
Common Mistakes and How To Avoid Them
Working with a self-leveling compound can be difficult, but avoiding common mistakes can make this project easier.
- Incorrect mixing ratios: Follow the manufacturer’s instructions for proper consistency and curing.
- Insufficient cleaning: Make sure the floor is completely clean and dry for a stronger adhesion.
- Rushed application: Take your time spreading the compound evenly to avoid lumps and bumps that may require rework.
Curing and Finishing the Floor
After applying the self-leveling compound, proper curing will give you a durable final result.
Curing Time
Allow the compound to cure overnight or according to the manufacturer’s recommendations. Much like allowing dough to rise for the perfect loaf of bread, giving your concrete floor time to cure properly is essential for achieving the best results. Curing time may vary depending on environmental conditions, product composition, and the thickness of the application.
Finishing Touches
Before installing new flooring, perform a final inspection for smoothness and evenness. Check that the compound is sufficiently dry and cured, then sand down any remaining imperfections if necessary.
Tips for a Long-Lasting Floor
Maintaining a newly leveled floor requires a few details. Make sure you have proper ventilation in the area while the compound cures, as this will help it set more evenly and quickly. Also, heavy foot traffic should be kept off the new floor for at least 24 hours or as recommended by the manufacturer so it can fully cure and harden.
