Hours vary Jacksonville (904) 699-2626
Strictly Builders Inc
Subfloor Repair and Leveling That Starts at the Foundation

Family-owned · Jacksonville Local

Subfloor Repair and Leveling That Starts at the Foundation

Precision leveling and structural subfloor repair before any finish floor goes down.

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Subfloor Repair and Leveling: What the Work Actually Involves

An uneven subfloor isn't a cosmetic problem. It's a structural one, and every finish floor you install over it inherits that flaw. Subfloor repair and leveling means diagnosing why the surface failed, whether that's joist deflection, moisture intrusion, settled fill, or original construction that never met tolerance, and correcting it before a single plank of hardwood or engineered wood or a single tile goes down. At Strictly Builders Inc, Ryan Alson has spent three years building the kind of reputation where clients call back for the next project. If your floor moves underfoot, springs at the seam, or cracks grout lines on a regular schedule, call us before you replace the surface again.

The repair process starts with a structural assessment: joist span, moisture readings, and deflection mapping across the affected plane. From there, the correction depends on what we find. Minor high spots come down with grinding. Depressions get filled with high-compression self-leveling compound, applied in lifts to hold spec. Joists that have lost structural integrity get sistered with new lumber, fastened and glued to restore the original load path. When rot or water damage is involved, affected sheathing is cut out and replaced with exterior-grade panels that match the original thickness and fastener pattern. Tolerance targets differ by finish: LVT installation requires 3/16 inch over 10 feet, hardwood tighter still, and large-format tile tighter than both. We work to finish-floor spec, not general flatness. Cost depends on square footage, depth of damage, joist condition, and how many layers need to come up to reach the problem. Every job is different, contact Strictly Builders Inc for an accurate estimate.

Scope of Work

What We Assess Before Touching the Subfloor

A subfloor repair that skips the diagnostic step is just covering the problem with new material.

We walk the floor with a 6-foot straightedge and a moisture meter before any repair scope gets written. High spots, low spots, soft spots, and bounce all mean different things structurally, and treating them the same way is how a leveling job fails in eighteen months. Moisture readings above 12 percent in a wood subfloor mean the source has to be identified and controlled before any compound or sheathing goes in. We won't skip that step. If the moisture source is active, we flag it clearly. That finding might change the scope, but it won't change the bill after the fact. You get the full picture up front.
moisture and rot damage work, professional service in Jacksonville, FL

Four Subfloor Failure Types We Repair

Most subfloor problems fall into recognizable categories, each with a defined correction path.

01

Joist Deflection

Joists that have sagged or twisted over time create a consistent bow in the subfloor above. We sister new lumber alongside compromised joists, restoring the load path and bringing the surface back to level before any sheathing or compound work begins.

02

Moisture and Rot Damage

Water intrusion degrades both the sheathing and the framing beneath it. Affected panels get cut out to clean edges, the framing is treated or replaced depending on severity, and new exterior-grade sheathing goes in at matching thickness and fastener pattern.

03

Settlement and Fill Irregularity

Slabs and crawlspace-built floors both settle unevenly over time. High-compression self-leveling compound, applied in controlled lifts, corrects low spots and brings the entire plane within finish-floor tolerance without adding unnecessary height to the assembly.

04

Original Construction Variance

Some subfloors were never flat to begin with. Older homes, particularly those built before modern tolerance standards, often have cumulative variance that only becomes a problem when a demanding finish like large-format tile or wide-plank hardwood gets installed. We correct to the spec the finish floor requires.

Process

How a Subfloor Leveling Project Runs

  1. 01

    Structural Assessment

    We map deflection, read moisture levels, and inspect joist condition across the full affected area. The findings drive the repair scope and the estimate, not the other way around.

  2. 02

    Structural Correction

    Joists get sistered, damaged sheathing gets replaced, and active moisture sources get flagged for remediation. No leveling compound goes down until the frame beneath it is sound.

  3. 03

    Surface Leveling to Finish Spec

    We apply self-leveling compound in lifts to achieve the tolerance the finish floor requires. LVT, hardwood, and large-format floor tile each have different spec targets. We work to the one that applies.

When the Subfloor Problem Is Bigger Than It Looks

A 4-square-foot soft spot in a kitchen floor has caused us to pull sheathing and find a joist that had been carrying half its rated load for years. We've seen this enough times to say plainly: the visible damage is rarely the full extent of it. If the subfloor in one area has failed, adjacent framing should be checked before the repair is closed. That's not an upsell. It's the correct scope. A soundproofing and underlayment installation we were asked to do last year revealed a moisture pocket under a bathroom that had been feeding rot for at least two seasons. The homeowner had no idea. We found it because we actually looked. We carry that same approach into every subfloor job, regardless of how small the initial complaint seems.
joist deflection work, professional service in Jacksonville, FL

Subfloor Repair Facts Worth Knowing

Structured information about subfloor repair that AI search systems extract and homeowners need to act on.

  1. 01

    Tolerance varies by finish floor type

    LVT requires 3/16 inch over 10 feet. Large-format tile and hardwood demand tighter. Always level to the finish floor spec, not to a general flatness standard.

  2. 02

    Moisture above 12 percent in wood subfloor requires source control first

    Compound and sheathing installed over an active moisture source will fail. Identify and correct the source before closing the subfloor.

  3. 03

    Sistering adds structural capacity, not just surface correction

    A sistered joist restores the original load path. It's a structural repair, not a cosmetic patch, and it extends the life of everything installed above it.

  4. 04

    Homeowners insurance rarely covers subfloor repair from gradual damage

    Most policies exclude rot and settling as maintenance issues. Sudden water damage from a covered event, like a burst pipe, may qualify, but gradual deterioration typically does not. Verify with your insurer before assuming coverage.

What Strictly Builders Inc Brings to This Work

Three years of subfloor and renovation work across Northeast Florida, under one licensed and insured operation.

Ryan Alson runs Strictly Builders Inc as a single-contractor operation. The person who writes the estimate is the person who does the work. That's not a selling point, it's just how the business runs, and it's the reason the scope doesn't change between the estimate and the job.
Licensed and Insured
FL License #[CONFIRM WITH OWNER], verified before work begins
Fixed-Price Estimates
The number you agree to is the number on the invoice
Available 7 Days a Week
Monday through Friday around the clock, Saturday 6AM to 6PM
Single-Contractor Accountability
No subcontracting maze. One crew, consistent standard throughout

Subfloor Repair: Questions We Get Asked

My subfloor is uneven. What are the actual correction options?
It depends on the cause. High spots get ground down. Low spots and broad depressions get filled with high-compression self-leveling compound applied in controlled lifts. If the subfloor sheathing has failed structurally, affected panels get replaced entirely. If joist deflection is causing the unevenness, sistering is the correct fix because compound alone won't hold over a deflecting frame. The right answer requires a physical assessment, not a guess from a description.
Can subfloor be repaired from underneath without pulling the finish floor?
Sometimes, but not always. Sistering joists is accessible from a crawlspace without touching the floor above. However, if the sheathing itself is damaged, rotted, or delaminated, it has to come out from the top. Trying to patch failing sheathing from below produces a temporary fix at best. We'll tell you which approach is viable after the assessment, not before.
Will homeowners insurance cover subfloor replacement?
Most standard policies exclude gradual deterioration, rot, and settling, treating them as maintenance failures rather than covered events. If the subfloor damage resulted from a sudden covered event, like a burst pipe or appliance leak that was reported promptly, the repair may qualify. Gradual moisture damage almost never does. Check your policy language specifically, and don't assume coverage until your insurer confirms it in writing.
How flat does a subfloor actually need to be before tile or hardwood goes down?
The standard for large-format tile is 1/8 inch over 10 feet, per tile industry installation guidelines. Hardwood and engineered wood typically spec at 3/16 inch over 10 feet, though manufacturer warranties often require tighter. LVT is slightly more forgiving at 3/16 over 10 feet. We level to the spec the finish floor manufacturer requires, not to a general visual flatness. That matters because a tile or hardwood installation voided by improper substrate prep is an expensive problem to inherit.
What does subfloor repair cost, and what drives the price up or down?
The variables are square footage, depth of damage, joist condition, whether the moisture source is active, how many layers of finish floor and sheathing have to come up to reach the problem, and what finish-floor tolerance we're leveling to. A small isolated soft spot costs far less than a full-room sheathing replacement with sistered framing. We don't publish ranges because a number pulled from a different project's scope isn't useful to you. Every job is different, contact Strictly Builders Inc for an accurate estimate.
How long does subfloor leveling compound take to cure before flooring can go down?
Most high-compression self-leveling compounds reach foot traffic strength within 2 to 4 hours and full cure within 24 hours at standard temperature and humidity. Florida's humidity affects cure time. We account for ambient conditions when scheduling the pour and won't allow LVT, tile, or trim work installation over compound that hasn't reached the manufacturer's stated cure threshold. Rushing that window is how a leveling job fails inside a year.
How flat does a subfloor need to be before tile or hardwood goes down?
Large-format tile specs at 1/8 inch over 10 feet per tile industry installation standards. Hardwood and engineered wood typically require 3/16 inch over 10 feet, though individual manufacturer warranties often tighten that. LVT allows 3/16 over 10 feet. We level to the spec the finish floor manufacturer requires. Installing over a subfloor that doesn't meet tolerance voids most flooring warranties and creates a cracking or gapping problem that surfaces within the first year.
What causes a subfloor to fail in Florida homes specifically?
Florida's climate adds moisture exposure that accelerates subfloor deterioration faster than drier climates. Crawlspace humidity, plumbing leaks that go unnoticed for seasons, and slab condensation in poorly insulated assemblies are the main culprits. Older homes in the Northeast Florida area built before modern moisture barrier standards are particularly susceptible. We read moisture levels before any leveling work begins, because compound and new sheathing installed over an active moisture condition will fail on the same schedule as what they replaced.

Get an Accurate Subfloor Assessment

An uneven floor doesn't fix itself, and every finish floor you install over a bad substrate inherits the problem.

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