Luxury vinyl plank (LVP) flooring offers durability and design flexibility, but a successful install starts with a flat, smooth subfloor. Small dips, high spots, or uneven patches can telegraph through the planks or compromise locking seams in floating installations. This guide explains typical levelness requirements, how to measure floor flatness, and practical fixes for concrete and wood subfloors. It also covers moisture tests, acclimation, and expansion gaps to help homeowners and DIYers plan a reliable LVP installation.
Understanding Levelness Requirements For LVP
LVP flooring requires a flat, smooth surface. Industry guidelines and most manufacturers specify a maximum variation of 1/8 inch in 6 feet or 3/16 inch in 10 feet. Some premium products with thicker wear layers and locking systems may tolerate minor deviations, but staying within these tolerances reduces the risk of visible seams, telegraphing, or premature wear. The exact tolerance can vary by product, so always check the installer instructions for the specific LVP line being used.
Severe irregularities—waves, deep dips, or high ridges—will compromise both the look and the performance of the floor. Before starting, inspect the entire area, including transitions to closets, hallways, and thresholds. If you detect deviations beyond the tolerance, plan leveling work first to ensure a durable, visually even installation.
How To Measure Floor Flatness
Begin with a long straightedge, typically 6 to 8 feet, or a laser level for larger spaces. Place the straightedge across the floor in multiple orientations and check for gaps between the edge and the surface. If any gap exceeds 1/8 inch in 6 feet or 3/16 inch in 10 feet, mark the area as a defect. Repeat checks after any temporary fixes. For small rooms, a 4-foot level can identify obvious high and low spots and guide leveling plans.
Documenting the high and low spots helps determine how much leveling material is needed and where to place patches or self-leveling compounds. It also helps verify that the room meets the manufacturer’s flatness criteria before LVP installation begins.
Fixing Floor Imperfections
High Spots
To address high spots on wood subfloors, remove excess material using a planer or sanding until flush with surrounding areas. On concrete, use a concrete grinder or diamond cup wheel to bring the surface down flat. After grinding, clean thoroughly to remove dust, which can affect leveling products and adhesive performance. If any gouges remain, fill them with an appropriate leveling compound and allow to cure before proceeding.
Low Spots
Low spots should be filled with a cementitious leveling compound or patching material. For larger dips, apply a self-leveling underlayment (SLC) per the manufacturer’s instructions, including priming and mixing requirements. Spread evenly with a trowel, and allow full cure time before testing flatness again. After leveling, vacuum, wipe, and re-check with the straightedge to confirm adherence to tolerances.
After Leveling
Once leveling is complete and the surface is dry, re-check the floor with a straightedge to confirm it remains within tolerance across all areas. If any area still exceeds the spec, repeat the leveling process before acclimation and installation. Only then should acclimation and installation proceed to minimize movement after the floor is laid.
Subfloor Types And Their Impact
Concrete slabs must be dry and structurally sound. Before leveling, perform moisture testing per manufacturer guidelines. Common methods include a calcium chloride test (often < 3 lbs/1000 sq ft/24 h) or non-destructive relative humidity (RH) testing (often target 75%–85% RH or lower, depending on product). Repair cracks, remove sealers or coatings that could impede leveling compounds, and prime if required before applying self-leveling products. A dry, flat concrete base reduces adhesive failure and ensures a smooth final surface.
Plywood or OSB subfloors should be structurally sound, free of squeaks, and properly fastened. Check for loose boards, soft spots, or damaged sheets and repair or replace as needed. Sand or plane high spots, and consider a patching compound for any remaining irregularities. If the substrate isn’t flat or stable, leveling with an appropriate compound is recommended before LVP installation. In both concrete and wood scenarios, follow the product’s specific guidance on subfloor preparation, primers, and underlayment requirements.
Acclimation, Moisture And Preparation
Acclimate LVP in the room where it will be installed for 48 to 72 hours, keeping temperature and humidity within the product’s recommended range. Proper acclimation helps prevent post-installation gaps or buckling. Store planks flat and away from direct moisture sources during acclimation.
Moisture testing is essential, especially on concrete slabs. Follow product guidelines for acceptable RH or moisture levels; if readings exceed thresholds, apply mitigation measures or postpone installation. For wood subfloors, ensure the moisture content is appropriate for the climate, typically within a tight range specified by the manufacturer, to minimize expansion or contraction after installation.
Installation Tips And Underlayment
If the LVP comes with an attached underlayment, skip adding a separate layer unless the product requires a specific underlayment for sound reduction or moisture protection. For floating installations, use the manufacturer-recommended underlayment to improve stability and acoustics, and to help accommodate minor irregularities within the tolerance range.
Expansion gaps are essential. Leave a minimum 1/4-inch expansion gap around the entire perimeter of the room and at any transition to other flooring types. Use spacers during installation and remove them only after the floor is fully finished. Stagger long seams and avoid placing joints directly over floor imperfections to minimize visibility and movement.
Common Mistakes And When To Call A Pro
- Skipping a thorough flatness check before starting the install.
- Ignoring moisture risk on concrete or deficient subfloor preparation.
- Not acclimating the planks to room conditions or failing to maintain consistent climate during installation.
- Neglecting expansion gaps or misplacing seams in large rooms.
- Using the wrong underlayment or ignoring product-specific subfloor requirements.
Some issues require professional expertise: persistent moisture above product thresholds, significant substrate damage, or rooms with substantial irregularities that exceed standard leveling capabilities. If leveling material keeps cracking, or if the substrate shows structural movement, consult a flooring professional to prevent future failures.
Frequently Asked Questions
Do I need to level concrete before LVP adhesive installation?
Yes. Leveling improves adhesive contact, reduces the risk of telegraphing, and ensures a stable retrofit. Always follow the product’s flatness specs and use leveling compounds when necessary to reach the required tolerance.
Can I install LVP over existing vinyl?
In many cases, yes, provided the existing vinyl is firmly bonded, clean, dry, and flat. Some installations may require removal of old vinyl for the best results. Always consult the LVP manufacturer’s guidelines for compatibility and surface prep requirements.