A corduroy road lays logs 15-25 cm in diameter and 3-4 m long side by side, at right angles to the direction of travel, over swamp or soft ground where gravel would sink. It is a stopgap: the logs rot in 3-5 years, the ride is rough, and 100 m of road made of 20 cm logs takes about 500 logs weighing 44-55 tonnes in total. Use it only where no other road type can cross.
Part of Road Construction Basics
A road of transverse logs laid over soft ground, which spreads wheel loads over the bog and stays on top of it.
Corduroy Floats A Load Over Soft Ground, At A Cost In Timber And Time
On firm ground a gravel base carries the load. On a bog it sinks. A layer of logs laid across the route works because it spreads each wheel’s load over many logs, which together act as a raft on the soft ground. The parent article gives the construction and the limits: rough ride, logs rotting in 3-5 years, a surface that heaves as logs decay unevenly, and a note to use it only where other options are impossible because it is labour-intensive and temporary.
What You Need
- Logs — 15-25 cm in diameter and 3-4 m long, straight enough to lie tightly together. Green wood is easiest to find.
- Stakes — to pin the logs.
- Edge logs — laid along both sides to stop the surface logs spreading.
- Cover material — soil, sand or gravel for a smoother surface.
- Axes, saws and ropes — to cut and drag logs. See Essential Tools.
Method: Lay The Logs
Step 1: Clear and mark the line Cut brush along the route. Mark the centreline.
Step 2: Lay the logs across the route Place logs perpendicular to the direction of travel, tight against each other. The parent warns that gaps make wheels drop and break.
Step 3: Pin them with stakes Drive stakes in beside the logs to hold them in place.
Step 4: Lay edge logs Put logs along both edges, parallel to the road, to hold the surface logs together.
Step 5: Cover the surface Spread soil, sand or gravel over the logs to smooth the ride.
Worked Example: Timber For 100 m
Inputs: logs 20 cm in diameter and 3.5 m long, laid side by side along 100 m; green wood at 800-1000 kg/m³, from the table in Common Material Weights.
- Logs needed: 100 m / 0.20 m per log = 500 logs.
- Volume of one log: π × 0.10² × 3.5 = 0.110 m³.
- Mass of one log: 0.110 × 800 = 88 kg to 0.110 × 1,000 = 110 kg.
- Total mass: 500 × 88 = 44,000 kg to 500 × 110 = 55,000 kg, so 44-55 tonnes.
Across the parent’s full range of diameters: 15 cm logs mean 667 logs per 100 m and 33-41 tonnes; 25 cm logs mean 400 logs per 100 m and 55-69 tonnes. A single log of 88-110 kg is a two-person lift.
Replacement: the logs rot in 3-5 years, so a kilometre of this road needs about 5,000 logs and 440-550 tonnes again after 3-5 years.
Common Mistakes
- Leaving gaps — wheels drop into them and axles break. Pack the logs tightly.
- No edge logs — the surface spreads and the cover washes out.
- Treating it as permanent — plan for rebuilding in 3-5 years, or upgrade to a gravel road once the ground can bear it.
- Using it where firm ground exists — it is labour-intensive for a rough result.
Safety
Rolling logs and soft ground
A log of 88-110 kg can crush a foot or roll back down a slope. Use ropes and levers, keep feet clear, and never stand downhill of a log being moved. Wet logs are slippery; do not run a loaded cart on rotted logs.
What’s Next
- Learn next: Gravel Road — the permanent alternative where the ground allows
- Combine with: Side Ditches — draining the approach