Proper subfloor preparation is arguably the most important factor in successful vinyl flooring installation. Even premium vinyl flooring installed over an inadequate subfloor will telegraph imperfections, develop premature wear patterns, and fail to achieve its expected lifespan. Conversely, thorough preparation creates a foundation that helps even budget vinyl look and perform its best.
Many installation problems blamed on product quality actually stem from subfloor issues. Understanding what your subfloor needs and how to achieve proper preparation ensures your vinyl flooring investment delivers the results you expect.
Understanding Subfloor Requirements
Vinyl flooring manufacturers specify subfloor requirements in their installation guidelines, and meeting these requirements typically affects warranty validity. The three fundamental requirements are flatness, smoothness, and dryness—each demanding specific assessment and remediation approaches.
- Flatness: No more than 3mm variance over 1.8 metres (most manufacturers)
- Smoothness: Free of ridges, bumps, and debris that could show through vinyl
- Dryness: Moisture levels within acceptable limits for your chosen product
- Structural soundness: No movement, squeaks, or failing areas
- Cleanliness: Free of dust, adhesive residue, paint, or other contaminants
Assessing Your Existing Subfloor
Before beginning any preparation work, thoroughly assess your current subfloor condition. This assessment determines what work is needed and helps estimate the time and materials required.
Checking for Flatness
Use a long straightedge—a 1.8 metre level works well—to check for dips and high spots across the entire floor. Slide the straightedge across the surface, noting any areas where light appears underneath (low spots) or where the straightedge rocks (high spots). Mark problem areas with painter's tape for later attention.
Pay particular attention to seams between sheets of plywood or particle board, transitions between different floor materials, and areas near walls where settling may have occurred. These locations commonly develop unevenness that affects vinyl installation.
Testing Moisture Levels
Moisture testing is essential for concrete subfloors and advisable for timber subfloors in areas with humidity concerns. For concrete, conduct either a calcium chloride test (measuring moisture vapour emission) or a relative humidity test using in-situ probes. Australian standards specify acceptable limits that your results should meet.
Preparing Concrete Subfloors
Concrete subfloors are common in Australian homes, particularly slab-on-ground construction. While concrete provides a stable base, it often requires preparation to meet vinyl flooring requirements.
Filling Cracks and Holes
Small cracks and holes should be filled with concrete patching compound and allowed to cure fully before vinyl installation. For larger cracks that might indicate structural movement, consult a building professional before proceeding—cosmetic repair may not address underlying problems.
Levelling Uneven Concrete
Self-levelling compound is the standard solution for uneven concrete subfloors. This cementitious product flows across the surface and self-levels to create a flat plane. For small areas, spot-application addresses localised problems. For extensively uneven floors, a full-floor pour may be necessary.
Before applying self-levelling compound, prime the concrete with the manufacturer's recommended primer. This ensures proper bonding and prevents moisture in the compound from being absorbed too quickly by the concrete.
Managing Concrete Moisture
If moisture testing reveals excessive levels, several approaches can address the problem:
- Moisture barrier coatings: Epoxy-based coatings that seal the concrete surface
- Moisture barrier sheets: Polyethylene sheeting installed over the concrete
- Extended drying time: For new concrete, allowing additional curing time
- Dehumidification: Running dehumidifiers to reduce ambient moisture
Preparing Timber Subfloors
Timber subfloors—whether solid timber boards or sheet materials like plywood or particle board—require different preparation approaches than concrete.
Securing Loose Boards
Squeaky or moving floor sections must be secured before vinyl installation. Screw down loose boards, ensuring screw heads sit slightly below the surface. For particle board or plywood, use screws at regular intervals across the entire floor to ensure consistent attachment to the joists below.
Sanding and Filling
Raised nail heads, rough areas, and ridges at sheet seams should be sanded flat. Use floor patching compound to fill gaps between boards, countersunk screw heads, and any other depressions. Allow filler to cure completely, then sand smooth.
Dealing with Existing Floor Coverings
Vinyl can sometimes be installed over existing flooring, but this isn't always advisable. Single layers of well-adhered vinyl or linoleum in good condition may serve as acceptable subfloors. Multiple layers, cushioned vinyl, damaged flooring, or loose materials should be removed. Carpet must always be removed—never install vinyl over carpet.
Final Preparation Steps
Regardless of subfloor type, final preparation ensures the surface is ready for vinyl installation.
Thorough Cleaning
Sweep or vacuum the entire subfloor, then clean with appropriate products to remove any remaining dust, grease, or residue. For glue-down installation, the subfloor must be completely free of contaminants that could prevent adhesive bonding. Even for floating installations, a clean surface prevents debris from causing bumps or noise under the vinyl.
Final Flatness Check
After all preparation work, conduct a final flatness check with your straightedge. Any remaining problems are much easier to address now than after installation begins. Pay particular attention to the transition areas near doorways where the flooring will meet adjacent rooms.
Acclimation Considerations
With the subfloor prepared, bring your vinyl flooring into the room for acclimation. The room should be at normal living temperature—between 18°C and 26°C—and the flooring should acclimate for at least 48 hours before installation. This allows the vinyl to adjust to the room's temperature and humidity, reducing post-installation movement.
Proper subfloor preparation takes time and effort, but it's time well invested. A properly prepared subfloor supports your vinyl flooring through years of use, allowing it to look and perform as designed. Rushing this stage or cutting corners often leads to problems that are difficult and expensive to remedy later.