A bad retaining wall job can cost you $5,000 to $15,000 in repairs—or worse, damage to your property. Before hiring a contractor, you need to verify their experience, credentials, and track record with similar projects. This checklist ensures you find someone qualified to handle the structural and drainage demands of retaining wall work.
Confirm Licensing and Insurance
Check your state's licensing board for active contractor licenses. Retaining wall contractors should hold a general contractor or specialty masonry/landscape contractor license, depending on your location. Call the licensing board directly rather than trusting what's listed on a website—contractors sometimes let licenses lapse.
Request proof of liability insurance (minimum $1 million) and workers' compensation. A contractor without workers' comp is risking your property if someone gets injured on the job. Ask them to add you as an additional insured on their policy.
Review Experience with Retaining Wall Specifics
Not all contractors have equal expertise in retaining walls. Ask:
- How many retaining wall projects have they completed in the last 3 years?
- What's the tallest wall they've built?
- Have they worked with the soil type and slope conditions on your property?
- Do they design walls in-house or work with an engineer?
Walls higher than 4 feet typically require structural engineering calculations and building permits. A contractor who skips this step is cutting corners. Verify they've obtained permits on previous jobs by checking municipal records.
Check References and Portfolio
Request at least three references from retaining wall projects completed in the last 2–3 years. Call them and ask specific questions:
- Did the wall shift, crack, or settle after completion?
- Did drainage issues arise (water pooling, wet basement, erosion behind the wall)?
- Did the project finish on time and within budget?
- Would they hire this contractor again?
Visit finished projects if possible. Look for signs of poor work: bulging, horizontal cracks, water seepage, or displaced blocks.
Evaluate Site Assessment and Quotes
A thorough contractor will spend 30–60 minutes assessing your property before quoting. They should examine:
- Soil composition and compaction
- Existing drainage and grading
- Tree roots and vegetation near the wall location
- Underground utilities (call 811 before the inspection)
- Water movement patterns during rain
Get at least three written quotes. They should include:
- Materials (block type, size, reinforcement)
- Excavation and site prep
- Drainage system details
- Backfill specifications
- Labor and timeline
- Warranty terms
Quotes for a 20-foot wall typically range $3,000–$8,000 depending on height, material (concrete block, stone, timber), and site access. If one quote is suspiciously low, ask why—they may be cutting corners on drainage or compaction.
Verify Building Permits and Code Knowledge
Retaining walls fall under building codes, especially regarding setbacks, height limits, and safety factors. Your contractor should:
- Obtain required permits before starting
- Understand local frost line depths (affects footing depth)
- Know setback requirements from property lines
- Be familiar with your city's soil bearing capacity standards
Review the building permit application they submit. It should reference soil reports or at least acknowledge soil conditions on the property.
Confirm Drainage Design
Drainage failure is the #1 cause of retaining wall problems. Confirm the contractor's plan includes:
- Perforated drain pipe at the wall base
- Gravel backfill (not soil) against the wall
- Proper slope away from the wall (minimum 5%)
- Weep holes every 4–6 feet if using solid materials
Ask what happens if water pools behind the wall after completion. A reputable contractor stands behind their drainage work.
Get Everything in Writing
The contract should specify:
- Project start and completion dates
- Total cost and payment schedule (avoid large upfront payments)
- Warranty length (at least 1 year for materials and labor)
- Change order procedures
- Site cleanup and restoration plan
Frequently Asked Questions
Q: How deep should a retaining wall footing be? Footings must extend below the frost line for your region (typically 24–48 inches) to prevent frost heave. Your contractor should know your local frost depth or confirm it with a soil engineer.
Q: Can I build a retaining wall myself? Walls under 3 feet might qualify for permit exemptions in some areas, but structural calculations and drainage design are critical—mistakes can cause thousands in property damage or safety hazards.
Q: How long does a retaining wall last? Well-built walls last 50+ years; poor drainage or compaction causes failures within 5–10 years. Material choice matters: concrete block lasts longer than timber, but stone and proper construction matter more than material alone.
Use Mercoly to compare vetted retaining wall contractors in your area and get matched with professionals who meet these standards.