- Subfloor prep determines whether your floor lasts five years or twenty-five.
- Most rigid-core LVP requires 3/16" flatness over 10 feet — tighter than most builder slabs.
- Grinding removes high spots; self-leveling fills low spots. Most Florida homes need both.
- Moisture mitigation is a slab-by-slab decision, evaluated during the consultation.
- Old adhesive comes off mechanically; chemicals are avoided.
- Installing over tile is almost always the wrong shortcut.
Why Subfloor Prep Matters
Every flooring problem we get called to diagnose — clicking, hollow spots, edges that lift, planks that peak, seams that gap — traces back to the subfloor more often than not. The plank is rarely the failure. The plane underneath it is.
Rigid-core waterproof LVP is engineered to be dimensionally stable, but it still needs a flat, dry, sound subfloor to perform as designed. Florida slabs, in particular, are rarely flat to the tolerance modern LVP requires.
What We Check at the Consultation
- Flatness across each room with a 10' straightedge.
- Slab moisture using a meter or visual cues (efflorescence, staining).
- Cracks and joints in the slab that may telegraph.
- Old adhesive residue from previous flooring.
- Tile bed thickness if tile is being removed.
- Plywood condition: fastener pop, soft spots, seam height.
- Transition heights at every doorway.
Subfloor prep from the homeowner's perspective.
- Preparation RequiredLight
Scope identified at consultation; homeowner involvement minimal.
- Installation ComplexitySignificant
Crew skill matters more here than anywhere else.
- Typical Project DurationLight
Half day to full day on most Florida slabs.
- Home DisruptionModerate
Loud and dusty during grinding; quiet during leveling cure.
- Furniture MovingMinimal
Rooms are already cleared by this phase.
- Noise LevelSignificant
Grinding is loud; consider out-of-house arrangements for sensitive ears.
- Dust LevelSignificant
Slab grinding generates fine dust; vacuum-equipped tools contain most of it.
- DIY SuitabilityMinimal
Specialized tools and judgment required.
- Maintenance After InstallationMinimal
None — prep is one-and-done.
- Overall Homeowner ReadinessLight
Trust the process and stay out of the work zone.
Flatness and Leveling
Most rigid-core LVP requires 3/16" of variation over 10 feet, with some products specifying 1/8" over 6 feet. Reading those numbers and walking across a builder slab in a 1990s Central Florida home is two different experiences — the math rarely agrees.
Grinding
Grinders remove high spots. Diamond-cup wheels on a dust-shrouded machine cut the surface down to plane without altering the slab structurally. Most Florida slabs need a few hours of grinding somewhere.
Self-Leveling Compound
Low spots get filled with self-leveler. The slab is primed, formed at room edges, and the leveler is poured to find its own level. Cure time is typically a few hours before walking and several hours before install.
Combined Approach
Most Florida slabs need both. We grind high spots first to avoid burying them in leveler, then pour leveler to address what remains. The result is a true plane for the new floor.
| Method | Best For | Typical Time | Dust / Mess |
|---|---|---|---|
| Grinding | High spots, ridges, adhesive residue | 2–6 hrs | High |
| Self-leveling | Low spots, dips, large variation | 4–8 hrs (with cure) | Low |
| Patch / skim | Small isolated defects | 30 min – 2 hrs | Low |
| Combined | Typical Florida slab | Half to full day | Medium |
Moisture in Florida Slabs
Florida slabs breathe. Even a well-poured slab moves moisture vapor through the surface, and homes built before modern vapor-barrier practices can wick noticeably. Rigid-core waterproof LVP is more tolerant than wood or laminate, but excessive moisture still causes problems — efflorescence between plank and slab, adhesive failure on glue-down installs, and the occasional musty smell.
We evaluate moisture during the consultation. Where mitigation is needed, we use moisture-control underlayments, vapor-control primers, or topical moisture-mitigation membranes. The right answer depends on the slab.
Wood Subfloors
Less common in Florida but present in many older homes and second-story additions. Plywood and OSB get inspected for:
- Fastener pop — re-screwed to joists.
- Soft spots — replaced or sistered as needed.
- Seam separation — sanded smooth or patched.
- Moisture content — measured with a meter; flag any reading above product spec.
- Squeaks — reattached to joists with construction screws.
Adhesive Residue and Tile Beds
Old adhesive comes off mechanically — scraping, grinding, or shot-blasting. Chemical strippers are avoided because residue can interfere with new adhesives, react with backing materials, or create off-gassing problems.
Tile removal leaves a thinset bed that has to be ground down to a clean plane. This is one of the most labor-intensive prep scenarios and usually adds a half day or more to the timeline.
Skipping the straightedge test
Slabs that look flat to the eye routinely fail a 10-foot test. The test takes minutes and saves a 20-year floor.Installing over tile
Grout lines telegraph through LVP, transitions become awkward, and future repair is much harder. Removal is the right call.Trusting a chemical adhesive remover
Residual chemicals create future problems. Mechanical removal is the standard for a reason.Ignoring slab moisture
Even waterproof LVP can have problems if a slab is actively wicking. A moisture meter check at the consultation is non-negotiable.
- Ask your installer to show you the straightedge test before the install begins.
- Insist that prep scope is itemized on your written proposal.
- Plan for grinding dust during prep day — relocate sensitive pets and electronics.
- If you're a 'tile-over' installer's customer, get a second opinion.
Bring the showroom home. Samples, measurements, and a clear plan — no pressure.
Serving Ocala, The Villages, and Marion County since 2009.
Homeowner questions, answered.
Why does subfloor prep matter so much?+
A rigid-core waterproof LVP plank is only as flat, dry, and stable as the subfloor beneath it. A perfectly engineered plank installed over an out-of-flat slab will hollow, click, or fail at the seams within a year. Subfloor prep is what makes a 20-year floor possible.
What flatness tolerance does LVP need?+
Most rigid-core LVP manufacturers spec 3/16" over 10 feet (some require 1/8" over 6 feet). That's tighter than most builder slabs in Central Florida are poured to. We measure flatness during the consultation and itemize any grinding or leveling needed.
How do you check subfloor flatness?+
A long straightedge — typically a 10-foot aluminum bar — laid across the subfloor reveals high and low spots. A laser or string line works on larger spans. We check rooms in multiple directions, not just along one wall.
What is self-leveling compound?+
A flowable cementitious mix that's poured onto a primed subfloor and allowed to find its own level. It fills lows and creates a flat plane for the new flooring. In Florida, it's often combined with grinding to address both highs and lows.
Do I need a moisture barrier on a slab?+
Sometimes. Many rigid-core LVP products are spec'd for direct installation over concrete slabs without a separate vapor barrier. Older slabs without an original poly underlayment, or slabs known to wick, may require a moisture mitigation product. We test or evaluate this during the consultation.
How is old adhesive residue handled?+
Mechanically — scraping, grinding, or shot-blasting depending on adhesive type and bond. Chemical solvents are avoided because residual chemicals can interfere with new adhesives or react with the LVP backing.
Can you install over my existing tile?+
Almost always the wrong call. Tile creates ridges at the grout lines that telegraph through LVP, raises overall floor height (creating issues at doorways and transitions), and locks in any future repair complications. Tile removal is the right answer in nearly every case.
What about plywood or OSB subfloors?+
Wood subfloors get inspected for fastener pop, soft spots, water damage, and seam separation. Loose boards get re-fastened, damaged sections replaced, and seams sanded smooth. Moisture content is checked with a meter.
How long does subfloor prep take?+
Most Florida slab homes need 2–6 hours of focused prep. Severe cases (uneven slabs, extensive moisture issues, mass tile removal residue) can take a full day. We identify scope at the consultation, not during the install.
Can I skip subfloor prep to save money?+
It's the most expensive 'savings' in flooring. Skipped prep shows up as hollow spots, peaking, gapping, or click failure within the warranty period — and warranty claims on improperly installed floors typically fail. Prep is the cheapest way to protect every other dollar in the project.