Quick Answer
Pricing a French drain job in Lexington starts with two numbers: trench cubic yards (length × 0.75 ft × 2.5 ft ÷ 27) and drainage stone yards (trench yards × 0.85, accounting for pipe and fabric volume). A standard 50-foot French drain runs roughly 3.5 cubic yards Gray Crushed Rock 1.5", $720 in stone, $400 in pipe and fabric, $1,800 in labor (8 hours, 2-person crew at $112.50 combined hourly), and bills at $3,400 to $3,800 for the homeowner — competitive across the Lexington-Bedford-Concord market.
Why Lexington Drainage Jobs Are Bid Differently
Lexington's mature lots — half-acre and larger, with established trees and finished landscapes — mean drainage trenches snake around root zones and under existing beds. The trench math is simple; the labor math is the variable. A clean 50-foot run takes 8 crew-hours; the same length through a Lexington back yard with three mature maples and an irrigation grid takes 14. Bid the labor honestly and your margin survives the surprises.
The EPA Stormwater Management guidance backs the basic French drain spec used here. Browse the French drain & drainage collection for current per-yard rates on the stone.
The Yard-Math Worksheet
Step 1: Calculate Trench Volume
For a standard 9-inch-wide × 30-inch-deep French drain trench:
Trench cubic yards = Length (ft) × 0.75 ft × 2.5 ft ÷ 27
A 50-foot run: 50 × 0.75 × 2.5 = 93.75 cubic feet ÷ 27 = 3.47 cubic yards trench volume.
Step 2: Calculate Stone Volume
Subtract pipe and fabric volume (about 15% of trench):
Stone cubic yards = Trench cubic yards × 0.85
3.47 × 0.85 = 2.95 cubic yards stone. Round up to 3 cubic yards ordered to allow for compaction and waste.
Step 3: Material Cost
- 3 yards Gray Crushed Rock 1.5" at delivered Lexington pricing
- 50 ft 4-inch perforated pipe
- 75 sq ft woven landscape fabric
- 2 cleanouts (T-fittings + pop-up emitters)
Material total: roughly $1,100 to $1,200 delivered.
Step 4: Labor Cost
- 2-person crew × 8 hours for a clean run = 16 crew-hours
- At $56.25/hour per worker (loaded rate): $900
- For a complex Lexington run: 2 × 14 = 28 crew-hours = $1,575
Step 5: Equipment + Disposal
- Mini-excavator rental (1 day): $350
- Spoils removal (truck + dump fee): $250 to $400 depending on disposal site
Step 6: Mark-Up + Profit
Industry standard for a residential drainage job in eastern MA: 30% over loaded cost. Your bid math:
- Loaded cost: $1,150 stone + $1,050 labor (avg) + $350 equipment + $325 disposal = $2,875
- 30% margin: $3,738
- Round to $3,800 for the homeowner
For the Lexington landscape supply routes, both Gray Crushed Rock 1.5" and Dense Pack ¾" to minus deliver same-week. Pre-book the materials when you sign the contract — spring lead time on bulk stone runs 5 to 7 days in mid-April.
Common Bristol/Middlesex Pricing Mistakes
Three pricing errors that cost contractors money on Lexington drainage jobs:
- Underestimating the spoils volume. A 50-foot trench produces 3.5 cubic yards of dirt that has to leave the property. If you're not billing the dump fee separately, you're absorbing $300 per job.
- Skipping the cleanout fittings. Inspections fail without cleanouts on either end. Adding them after the trench is filled doubles the labor.
- Pricing labor at unloaded rates. A $25/hour worker actually costs $56 to $62/hour after taxes, insurance, vehicle, and overhead. Bid the loaded rate.
For the materials side of these jobs in adjacent towns, see the Top 5 Driveway Base Materials for Bristol County Properties read for the layered-stone logic that translates to drainage work.
Crew Logistics for a Single-Day Lexington Drain
- 7:00 AM — Stone and pipe delivered to driveway staging area
- 7:30 AM — Mini-excavator on site, layout marked
- 8:00 AM — Trench excavation begins
- 11:00 AM — Trench complete, fabric and pipe drop in
- 12:00 PM — Lunch / first stone load placed
- 1:00 PM — Stone backfill (use the How to Build a Dry River Bed in a Waltham Backyard walkthrough on April 14 for the same backfill technique)
- 3:00 PM — Cleanouts installed, surface graded
- 3:30 PM — Disposal run with spoils
- 4:30 PM — Day complete; homeowner walkthrough
For the 2026 follow-up on new-construction drainage spec in Hanover, see the 2026 new construction Hanover read.
What This Means for You
Three numbers — trench volume, stone volume, loaded labor — and a Lexington drainage job that pencils out at $3,800 with 30% margin protected. Skip the math and you're guessing. Pair this worksheet with the upcoming How to Layer Annuals into a Mulched Newton Bed read on April 26 for the post-drainage finish work that adds revenue per visit.
