The Foundation of Every Great Floor: Subfloor Prep Essentials for Professional Installers

Before a single plank, tile, or coating is laid, the success of any flooring installation hinges on one critical phase: subfloor preparation. Whether you’re working with Luxury Vinyl Plank, Engineered Hardwood, Carpet Tiles, or Epoxy Flooring, a properly prepped subfloor ensures long-term durability, warranty compliance, and client satisfaction.

“The finished floor is only as good as what’s underneath it,” says Darren M., a commercial flooring foreman with 20+ years in the trade.

Why Subfloor Prep Matters

• Prevents movement and squeaks

• Ensures even wear and finish

• Reduces adhesive failure risk

• Protects against moisture damage

Key Tools & Materials

• 6-ft. level or laser level

• Straight edge

• Moisture meter (RH or calcium chloride)

• Self-leveling compound

• Trowel and gauge rake

• Patch/skim coat materials

• HEPA vacuum

• Floor grinder or sander

Step-by-Step Subfloor Prep Process

1. Evaluate the Substrate

Check for dips, humps, and damage. Use a straightedge and level to map high and low areas.

2. Check Moisture Levels

Always perform a moisture test:

• Concrete: RH probe or calcium chloride

• Wood: Pin-style moisture meter
  Results must meet flooring product specs.

3. Clean the Surface

Remove dust, debris, grease, and old adhesives. A clean substrate improves bonding and finish quality.

4. Repair Cracks or Gaps

• Use patching compound on plywood joints or concrete cracks

• Sand flush with surrounding floor once cured

5. Apply Primer (if needed)

Some leveling compounds require a primer for better adhesion and to prevent air bubbles.

6. Use Self-Leveling Compound

Pour and spread compound with a gauge rake. Use a smoothing tool and allow it to cure per manufacturer guidelines.

7. Final Sand & Vacuum

Once cured, lightly sand to remove surface tension and vacuum thoroughly with HEPA filtration.

“Don’t rush this part. A perfect prep job saves hours down the line,” advises Christina L., certified flooring installer.

Special Considerations by Flooring Type

• LVP/LVT: Evenness is crucial. No more than 3/16″ over 10 feet.

• Engineered Hardwood: Must be dry and rigid. Avoid deflection.

• Carpet Tiles: Level surface prevents tile creep and visible seams.

• Epoxy: Grind or shot-blast surface. Moisture and profile are critical.

Common Mistakes to Avoid

• Skipping moisture testing

• Ignoring small dips or ridges

• Using the wrong patching compound

• Not allowing time for compound curing

• Failing to remove old adhesive residues

Quick Checklist for Installers

✅ Subfloor flat within tolerances
✅ Clean, dry, and debris-free
✅ All cracks patched or filled
✅ Moisture test results documented
✅ Leveling compound fully cured