How to put laminate flooring on concrete
To put laminate flooring on concrete, first prepare the subfloor by cleaning, leveling, and repairing cracks. Test thoroughly for moisture and install a 6-mil vapor barrier if needed. Lay an appropriate underlayment, acclimate the planks, and then click them together, maintaining expansion gaps around the perimeter for a successful installation.
Installing laminate flooring over a concrete slab is a common and achievable DIY project. Concrete is a stable subfloor, but it requires specific preparation steps to ensure your laminate lasts. You’ll need to address moisture, levelness, and cleanliness before laying any planks.
Prepare the concrete subfloor
The most critical step is preparing your concrete subfloor. Any imperfections can transfer through to the laminate, causing it to creak, loosen, or even crack over time. Start by inspecting the floor for cracks or holes. Fill any significant cracks or divots with a concrete repair compound. Allow it to cure completely according to the manufacturer’s instructions.
Next, check for levelness. Most laminate manufacturers require the subfloor to be level within 3/16-inch over a 10-foot span. Use a long, straight edge or a laser level to identify high spots or low spots. High spots can be ground down with a concrete grinder. Low spots can be filled with a self-leveling concrete compound. Again, ensure any patches are fully cured and dry.
Test for moisture
Concrete slabs, especially those at ground level or below, can emit moisture. Excess moisture is laminate flooring’s worst enemy, leading to swelling, warping, and mold growth. You must test for moisture before proceeding.
The simplest test is the plastic sheet method. Tape a 3-foot by 3-foot piece of plastic sheeting tightly to the concrete floor, ensuring all edges are sealed with tape. Leave it in place for at least 24 hours. After 24 hours, check the plastic and the concrete underneath. If there is condensation on the plastic or the concrete appears wet or discolored, you have a moisture problem. You will need to install a reliable moisture barrier system, such as a heavy-duty polyethylene vapor barrier (6-mil or thicker) or a specialized liquid-applied vapor barrier, before installing the laminate.
Choose the right underlayment
Laminate flooring requires an underlayment. When installing over concrete, the underlayment serves multiple purposes: it provides a moisture barrier, cushions the floor, helps with sound deadening, and smooths out minor imperfections. You need an underlayment specifically designed for laminate flooring and approved for use over concrete. Many laminate products come with an attached underlayment, but if yours doesn’t, you’ll need to purchase it separately.
Look for underlayments that include a built-in moisture barrier, often a 6-mil polyethylene film. If your underlayment doesn’t have a moisture barrier, you must install a separate 6-mil polyethylene vapor barrier first. Overlap the seams of the vapor barrier by at least 6 inches and tape them securely with moisture-resistant tape. Roll the underlayment out perpendicular to the direction you plan to lay the laminate planks, ensuring a tight fit without gaps or overlaps. Trim excess material as needed.
Acclimate the laminate flooring
Before installation, allow the laminate planks to acclimate to the room’s temperature and humidity for at least 48 hours. Keep the boxes flat in the room where they will be installed. This allows the material to expand or contract to its stable state, preventing issues after installation.
Install the laminate flooring
Most modern laminate flooring uses a click-lock or tongue-and-groove system, allowing planks to be joined without glue or nails. Always follow the specific installation instructions provided by the manufacturer of your chosen flooring.
Start along the longest, straightest wall. You’ll likely need to cut off the tongue side of the first row of planks that faces the wall. Maintain an expansion gap of approximately 1/4-inch to 1/2-inch (6mm to 13mm) around the perimeter of the room, including against walls, cabinets, and doorways. Use spacers to ensure a consistent gap. This gap allows the laminate to expand and contract with changes in temperature and humidity.
Lay the first row of planks, connecting the short ends. For subsequent rows, stagger the end joints by at least 6 inches to create a stronger, more aesthetically pleasing floor. You can typically achieve this by using the offcut from the previous plank to start the next row. Continue laying planks, locking them together by angling the tongue into the groove and pressing down. You may need a tapping block and a rubber mallet to gently tap the planks into place, ensuring a tight fit without damaging the edges.
When you reach the last row, you may need to rip (cut lengthwise) the planks to fit the remaining space. Measure the distance between the installed flooring and the wall, subtracting the expansion gap. Use a pull bar to snug the last row of planks into place against the wall.
Finish the installation
Once all planks are laid, remove the spacers. Install baseboards or quarter-round molding around the perimeter of the room to cover the expansion gap. Do not nail the molding directly into the laminate planks; nail them into the wall or subfloor. This allows the laminate to move freely.
Install transition strips (such as T-molding or reducers) in doorways or where the laminate meets another flooring type. These strips also need to be secured to the subfloor, not the laminate.
Common Mistakes When Installing Laminate on Concrete
| Step | Tools/Materials | Typical Mistake | Consequence |
|---|---|---|---|
| Subfloor Preparation | Leveling compound, grinder, concrete patch | Skipping or inadequately preparing the concrete | Cupping, warping, squeaking, or cracking of laminate planks |
| Moisture Testing | Plastic sheeting, tape | Not testing for moisture or ignoring results | Swelling, buckling, mold, and mildew growth |
| Underlayment/Moisture Barrier | 6-mil poly sheeting, appropriate underlayment | Using the wrong underlayment or omitting a moisture barrier | Moisture damage, voided warranty, reduced lifespan |
| Expansion Gaps | Spacers, measuring tape | Not leaving adequate expansion gaps around the perimeter | Buckling or lifting of flooring when humidity or temperature changes |
| Acclimation | Laminate flooring boxes | Installing laminate immediately without acclimation | Gaps appearing between planks or planks buckling after installation |
FAQ
Can I install laminate flooring directly over existing tile on a concrete slab?
Generally, no. Laminate requires a flat, stable subfloor. If the existing tile is perfectly flat and adhered securely, some manufacturers might allow it with a specific underlayment, but it’s often recommended to remove the old tile to ensure a proper installation and avoid issues with height or unevenness.
What is the best type of underlayment for laminate over concrete?
The best underlayment includes a built-in 6-mil polyethylene moisture barrier and offers good cushioning for sound and comfort. Always check the laminate manufacturer’s recommendations, as some may specify a particular type or thickness.
How do I fix a soft or spongy laminate floor over concrete?
A soft or spongy feel usually indicates an issue with the subfloor or underlayment. It could be unevenness, inadequate moisture protection, or the underlayment itself is failing. You may need to pull up the laminate in that area to inspect and repair the subfloor and underlayment before reinstalling.
Can I use laminate flooring in a basement with a concrete floor?
Yes, laminate flooring can be used in basements, but it’s crucial to ensure proper moisture control. A robust 6-mil vapor barrier and an underlayment with moisture-blocking properties are essential. Always test for moisture and address any issues before installation.