Repair a pothole by digging it out to sound material, refilling it with gravel in compacted layers, and crowning the patch slightly above the surrounding surface so that it compacts down; repair a washout by first finding and fixing the drainage fault that caused it, then rebuilding the road cross-section from the base up. A washout of 1.5 m by 4 m and 0.5 m deep needs 3 m³ of gravel, which is 4-9 cart loads. Filling over a soft base only hides the pothole for a season.
Part of Road Construction Basics
Fixing local failures of a gravel road surface, from a pothole a few centimetres deep to a washout that has cut through the whole cross-section.
A Pothole Is A Drainage Symptom, And A Washout Is A Drainage Failure
Water collects in a low spot, softens the base and wheels pound it into a hole. If you fill the hole without removing the soft base, the new gravel sinks and the hole returns. A washout is the same process at larger scale: water has crossed or run along the road and carried the road away. The parent says that a washout means drainage failed, and the first job is to find and fix the drainage problem.
What You Need
- Gravel — the same grade as the road surface. See Gravel Road.
- Shovels, picks and a tamper. See Essential Tools.
- A cart for washouts.
- Culvert material where water crosses. See Culverts.
Method: Repair Potholes And Washouts
Potholes
Step 1: Dig out to sound material Remove all soft, wet material until you hit firm base. The parent says not to fill over a soft base.
Step 2: Fill in layers Add gravel in layers and compact each. Use the parent’s limit of 15-20 cm per layer for fill, so a shallow pothole is one layer. See Compaction Methods.
Step 3: Crown the patch Leave the patch slightly above the surrounding surface, because it will compact down.
Washouts
Step 1: Fix the drainage first Find where the water came from. Clear the ditch, repair the culvert, or enlarge it.
Step 2: Rebuild from the base up Rebuild the road cross-section: subgrade, base, surface.
Step 3: Install or enlarge culverts Do this if water is overtopping the road. Culverts covers cover depth and wheel loads.
Step 4: Consider moving the road If the spot is a natural drainage path or flood-prone, the parent suggests rerouting.
Worked Example: Gravel For A Pothole And A Washout
Inputs: gravel at 1,400-1,800 kg/m³ from Common Material Weights; cart capacity 600-1,200 kg from Carts and Wagons.
Pothole 0.6 m × 0.5 m × 0.15 m. Volume = 0.6 × 0.5 × 0.15 = 0.045 m³. Mass = 0.045 × 1,400 = 63 kg to 0.045 × 1,800 = 81 kg. A few barrow loads.
Washout 1.5 m × 4 m × 0.5 m. Volume = 1.5 × 4 × 0.5 = 3 m³. Mass = 3 × 1,400 = 4,200 kg to 3 × 1,800 = 5,400 kg.
- Cart loads: 4,200 / 1,200 = 3.5, so 4 loads at best; 5,400 / 600 = 9 loads at worst. So 4-9 loads.
- Layers: a depth of 0.5 m is at least three layers of 15-20 cm each (0.5 / 0.20 = 2.5 and 0.5 / 0.15 = 3.3), each compacted before the next.
Compacted gravel is denser than loose gravel, so the real mass is more than these figures, and 3 m³ of loose gravel will compact to less than 3 m³. Haul more than the arithmetic says and check the depth after the first layers.
Common Mistakes
- Filling over soft material — the patch sinks; dig to sound base.
- A single thick layer — the bottom stays loose. Compact in layers.
- Crowning too little — the patch settles below the road and the hole returns.
- Fixing the surface only — if the drainage fault remains, so does the washout.
- Rebuilding in the same place forever — if the road keeps washing out at one spot, move it, as the parent says.
Safety
Washouts hide drops and soft ground
A washout may be deeper than it looks, with undercut edges that collapse. Probe the edge before standing near it, do not work alone, and keep carts and animals off the repair until the layers are compacted.
What’s Next
- Learn next: Seasonal Maintenance Schedule — finding failures before they grow
- Combine with: Side Ditches — fixing the drainage that caused them