Subfloor Repair and Replacement Cost: Pricing Guide for Contractors
Subfloor repair and replacement costs range from $2-$8 per square foot depending on the scope. Minor leveling with self-leveling compound runs $1.50-$3.00/sq ft. Plywood overlay costs $2.50-$4.00/sq ft. Rotten subfloor tear-out and replacement costs $4-$8/sq ft. Moisture mitigation systems add $2-$4/sq ft. Always inspect the subfloor before quoting the finished flooring to avoid costly surprises.
Every flooring installation is only as good as the subfloor beneath it. Subfloor problems — rot, moisture, unevenness, squeaks — are discovered on nearly half of all renovation flooring jobs, and how you handle them determines both your profitability and your reputation. Contractors who include subfloor assessment in their estimating process avoid the nightmare scenario of discovering rotten plywood mid-project with no budget to fix it. This guide covers pricing for every common subfloor repair scenario.
Self-Leveling Compound Pricing
Self-leveling compound (SLC) is the standard solution for uneven concrete and plywood subfloors. Material cost runs $0.75-$1.50/sq ft for a 1/4-inch pour depth. Deeper pours increase proportionally — 1/2-inch depth doubles the material cost. Primer for the substrate: $0.15-$0.25/sq ft. Labor for SLC application: $1.00-$2.00/sq ft including mixing, pouring, and spreading. Total installed cost: $1.50-$3.50/sq ft for standard depths. SLC is required when the subfloor is out of tolerance for the finished flooring — most products require flatness within 3/16-inch per 10-foot span. For large areas, SLC is more cost-effective than grinding. For small dips and voids, use floor patching compound at $0.50-$1.00/sq ft. Always check the SLC compatibility with your adhesive or underlayment system — some products are not compatible with certain moisture barriers.
Plywood Overlay Installation
Plywood overlay is used when the existing subfloor is structurally sound but has surface damage, excessive squeaking, or needs additional thickness for height transitions. Material: 1/4-inch luan plywood at $0.40-$0.70/sq ft, or 3/8-inch to 1/2-inch CDX plywood at $0.75-$1.50/sq ft. Fasteners (screws recommended over nails for squeak prevention): $0.10-$0.20/sq ft. Labor: $1.00-$1.75/sq ft for cutting, fitting, fastening, and seam treatment. Total installed: $1.75-$3.50/sq ft. Important: adding plywood raises the floor height, which affects door clearance and transitions to adjacent rooms. Account for door trimming ($15-$30/door) and transition adjustments in your estimate. For tile installations, use cement backer board (HardieBacker, Durock) instead of plywood at $1.50-$2.50/sq ft installed.
Rotten Subfloor Tear-Out and Replacement
Water damage and rot are most common around toilets, tub/shower areas, dishwashers, and exterior doors. Localized repair (under 50 sq ft): $5-$8/sq ft including tear-out, joist inspection, new plywood, and blending. Large-area replacement (over 50 sq ft): $4-$6/sq ft at scale. The process includes removing the damaged plywood section, inspecting and potentially sistering joists ($50-$150 per joist if damaged), installing new 3/4-inch tongue-and-groove plywood, and fastening with screws. Disposal of rotten material: $50-$100 per load. If rot extends to floor joists, the repair becomes structural work — communicate this to the client immediately and adjust the scope. Include a contingency note in your original estimate: "Subfloor condition to be confirmed upon removal of existing flooring. Additional repair costs may apply if concealed damage is discovered." This clause protects you legally and sets expectations.
Moisture Mitigation Systems
Concrete subfloors frequently have excessive moisture that will destroy flooring if not addressed. Moisture testing (calcium chloride or relative humidity probe): $50-$150 per test location — conduct at least 3 tests per 1,000 sq ft. If moisture exceeds acceptable levels (3 lbs/1,000 sq ft for calcium chloride, or 75% RH for in-situ probe), mitigation is required. Epoxy moisture barrier: $2.00-$4.00/sq ft installed — the most reliable option for high-moisture concrete. Sheet membrane moisture barrier: $1.50-$3.00/sq ft installed. Topical sealers: $0.75-$1.50/sq ft — suitable for borderline moisture levels. For wood subfloors over crawl spaces, moisture issues often stem from inadequate crawl space ventilation or vapor barrier. Recommend crawl space encapsulation ($3-$7/sq ft of crawl space) as the root-cause fix rather than just treating the symptom at floor level.
Squeaky Subfloor Repair
Squeaky subfloors are caused by loose plywood moving against nails or joists. This is a common issue in homes over 15 years old. Screw-down repair from above (when subfloor is exposed): $0.50-$1.00/sq ft — drive screws every 6-8 inches along joists to pull the plywood tight. This is the most effective fix and should be done on every renovation flooring project where the subfloor is exposed. Repair from below (through existing ceiling): $1.50-$3.00/sq ft — requires access from a basement or crawl space, using construction adhesive and screws from below. Squeak reduction through existing flooring (without removal): $0.75-$1.50/sq ft using specialized breakaway screws (Counter-Snap or Squeeeeek No More kits). Include squeak repair as a recommended add-on in every estimate where old subfloors are involved. The cost is modest and clients highly value squeak-free floors.
How to Estimate Subfloor Work Accurately
The biggest challenge with subfloor pricing is that you often cannot fully assess the condition until the existing flooring is removed. Protect yourself with these strategies. During your site visit, check for soft spots by walking the floor, look for water stains on ceilings below, check around toilets and tubs for spongy areas, and use a moisture meter on exposed subfloor areas. Include a subfloor inspection line item in every renovation estimate at $0-$200 (some contractors build it into overhead). If you suspect issues, add a subfloor allowance: "Subfloor allowance — $XXX for potential leveling or repairs. Will be credited if not needed." This sets client expectations and prevents scope creep. For known subfloor problems, price the repair as a separate section in your proposal with detailed line items. Never bury subfloor costs in your per-square-foot installation rate.
Frequently Asked Questions
Subfloor repair ranges from $1.50-$8.00/sq ft depending on the scope. Leveling costs $1.50-$3.50/sq ft, plywood overlay runs $1.75-$3.50/sq ft, and rotten subfloor replacement is $4-$8/sq ft. Always itemize subfloor work separately from the finished flooring installation.
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