The price to fill a void under a concrete slab varies by size, access, material choice, and labor. Typical projects span from repairing a small crawlspace gap to stabilizing a large slab foundation, with cost drivers including material type, excavation, and delivery. This article presents concrete price ranges in USD and practical budgeting guidance for U.S. buyers.
| Item | Low | Average | High | Notes |
|---|---|---|---|---|
| Void filling (per cubic yard concrete) | $250 | $350 | $500 | Typical mix, standard delivery |
| Foam injection (urethane/polyurethane, per ft³) | $2.50 | $4.00 | $7.00 | Used for small voids and crack sealing |
| Labor (per hour, crew of 2-3) | $60 | $90 | $140 | Regional variance applies |
| Excavation or access prep (flat rate) | $200 | $600 | $1,200 | Access can raise costs |
| Permits/inspections | $0 | $100 | $500 | Depends on jurisdiction |
What buyers typically pay for filling a void under a concrete slab
Prices usually range from $1,000 to $6,000 for small to mid-size slab areas, depending on the void’s depth, access, and chosen method. A simple foam-fill in a crawl space might land near the $1,000–$2,500 range, while larger concrete pours or thorough excavation-and-fill projects can reach or exceed $5,000. Assumptions: standard residential slab, normal access, Midwest-to-South labor rates.
Cost components split: materials, labor, and site prep
Major cost components include materials (concrete or foam), labor, and site preparation. The table below shows a typical breakdown for a mid-size void under a slab.
| Component | Low | Average | High | Notes |
|---|---|---|---|---|
| Materials (concrete mix or foam) | $250 | $1,000 | $2,500 | Choice of material impacts long-term performance |
| Labor | $400 | $1,500 | $3,000 | Includes crew mobilization and finishing |
| Excavation/Access prep | $200 | $600 | $1,200 | Shoring or trenching may be needed |
| Delivery/Materials handling | $50 | $200 | $600 | Heavy loads add cost |
| Permits/Inspection | $0 | $100 | $500 | Regional requirements vary |
Key variables that most influence the final quote
Two critical drivers are void size and access complexity. Void volume below 10 cubic yards often stays near $1,000–$3,000, but volumes above 20 cubic yards can push costs toward $5,000 or more. Regional labor rates also shift totals by 10–25% between markets. A threshold example: depth > 4 feet or more than 2 access points typically adds labor and equipment time.
Concrete fill vs. foam injection: price contrasts by scenario
Foam injection is usually cheaper for small voids but may not be suitable for load-bearing stabilization. Per cubic foot pricing ranges from $2.50 to $7.00 depending on foam type and cure requirements. For larger voids, conventional concrete fill or grout pours can be more cost-effective per volume, often around $250–$500 per cubic yard including delivery. Assumptions: residential slab under 2,000 sq ft, standard load requirements.
Regional price variations you should expect
Prices shift with regional demand and labor costs. In the West Coast, expect higher labor and permitting fees, whereas the Southeast may offer lower labor rates but increased weather-related delays. Typical regional delta: up to 25% in total project cost between high-cost and low-cost markets. Assumptions: non-urban settings, standard access, typical permit rules.
Labor time and crew size impact on the bottom line
A two-to-three-person crew is common for mobilization, excavation prep, and install. Estimated labor hours often range from 6 to 20 hours for mid-size projects, with higher-end work needing more time for compaction and finish work. Use the formula to estimate labor cost.
How to reduce the price without sacrificing safety or longevity
Smart scope control can save money. Limit unnecessary demolition, reuse stable edges when possible, and select a foam option only for voids not affecting structural stability. Scheduling during off-peak seasons, bundling related slab projects, and obtaining multiple quotes helps keep costs in check. Assumptions: no structural repair required beyond void fill.
What to ask a contractor before agreeing to a price
Request a detailed quote with itemized line items for Materials, Labor, and Prep. Ask about curing times, load ratings, and any required inspections. Ensure the quote includes delivery, disposal, and any potential contingency. Assumptions: project remains within residential building code.