How to Level a Floor: Techniques for a Flawless Finish

How to Level a Floor: Techniques for a Flawless Finish


If you're a DIYer considering leveling a floor, then you've come to the right place. Constructing a level surface is essential for any construction project and can easily add more value to your property. Whether it's patching up gaps or minor drops, understanding how best to approach leveling your uneven floor will help turn a rudimentary surface into something state-of-the-art – so let's get started on learning how to achieve a flawless finish.


woodworking tools on a table

Examine the Room Slope

A rotating laser level is a highly effective tool to assess the overall slope of a room. Positioning the laser level at the room's center, projects an even line onto all walls. Take measurements of the distance between the laser line and the floor at various points around the perimeter to determine if there is a noticeable slope.


rotating laser level

Search for Small Inconsistencies

To look for small inconsistencies in the floor, place a long straightedge parallel to one side wall and about a foot away from it. Check for any gaps between the straightedge's bottom and the floor as you move it over the floor. The number and size of the gaps will help determine the appropriate method for subfloor correction.

Move the straightedge in 1-foot increments across the floor and measure the distance between its bottom and the floor at various locations. If you notice the floor sagging at one spot, it could indicate a damaged floor joist. Strengthening the joists may be necessary to fix the sinking floor.

Choose a Strategy

If the gaps beneath the straightedge are irregular dips or sags that cover an area of less than 4 inches wide and are less than 1/2 inch deep, replacing the subfloor with plywood sheets will likely level out the floor enough to support most new flooring options.

For broader dips or shallow waves that exceed 4 inches in width, using a liquid self-leveling compound to level out those areas is the best solution. Once the compound dries, the floor will be even and smooth, ready for any new floor covering.

If you notice drooping along a line in one section of the floor, it may be a sign of a warped or fractured floor joist that is no longer providing sufficient support. To repair the issue, a sister joist should be placed beside the faulty joist to strengthen it.


liquid self-leveling compound being applied on a floor surface

Plan the Layout

When laying out the plywood sheets, it's important to orient them with the long dimension perpendicular to the floor joists. Additionally, ensure that the joints between the underlayment sheets are staggered by about half a sheet's length from the joints in the subfloor. To provide support for the ends, position the short sides of the plywood sheets at the center of the joists.

Be sure to plan the arrangement with a 1/4-inch expansion space between each sheet to accommodate any potential movement or shifting.


Attach the Sheets

Begin by placing the first sheet against one of the walls, leaving a 1/4-inch gap along the edge. Secure the sheet to the floor joists with 2 1/2-inch screws, spacing them 6 to 8 inches apart along each joist. Be sure to recess the screw heads slightly below the surface of the plywood.

If more than one sheet is needed to cover the first row, trim and insert the next sheet, leaving a 1/4-inch gap between the ends of the sheets. Fasten the second sheet in the same manner as the first. Continue to install the remaining sheets in the first row, cutting the last sheet if necessary, while remembering to maintain the 1/4-inch gap between each sheet.


Finish the Installation

Complete the second row by using full-width sheets of plywood, but trim the first sheet to ensure that the end joints between the sheets are offset by approximately 4’ from those in the first row. Be sure to maintain a 1/4-inch space between each layer.

Proceed to install the remaining plywood sheets throughout the room, securing them to the floor joists in the same manner. For the final row of plywood, cut the sheets to fit the remaining space, leaving a 1/4-inch gap around the wall.


Fill the Gaps

Mix the self-leveling compound and use a trowel to apply it over the seams and screw heads. It is important to allow the compound to dry completely before sanding the seams and screw heads until they are smooth. Finally, prior to starting the installation of the new floor, thoroughly vacuum the entire floor to remove any dust and debris.

There is nothing better than a finished, leveled floor. The satisfaction that comes with knowing it was done right and looks professional is unbeatable. Knowing how to level a floor is an essential skill for any DIYer looking to upgrade their home. Whether your mission is purely functional or decorative, you'll be able to proudly stand back and admire your hard work. Leveling floors doesn't have to be intimidating; just remember that with practice comes mastery. Finally, don't forget that a well-leveled floor will last years if properly maintained, giving you ample time to enjoy your handy work!