Road Construction Basics

8 min read

Road Construction Basics

Roads are the circulatory system of any settlement. Without passable roads, every trip takes three times as long, carts break down, injuries happen, and trade becomes impractical. Building even simple roads is one of the highest-return infrastructure investments a small group can make.

The ancient Romans understood this — their roads lasted two thousand years. You don’t need Roman engineering to build a serviceable road, but you do need to understand drainage.

The single most important principle: water is the enemy of roads. Every design decision exists to get water off the road surface and away from the roadbed.

Road Types & Selection

Cleared Track

The simplest “road” — a marked path with obstacles removed.

Construction:

  1. Walk the route and mark it (stakes, blazes on trees, cairns)
  2. Remove rocks, fallen trees, and brush from the path
  3. Cut stumps flush with the ground
  4. Fill holes and level the worst bumps

Time investment: 1-2 people can clear 1-2 km per day through moderate terrain.

Limitations: Turns to mud in rain, erodes on slopes, overgrows quickly. Suitable only for foot traffic and pack animals. Not adequate for wheeled vehicles.

Gravel Road

The workhorse of pre-industrial transportation. A properly built gravel road handles carts, wagons, and foot traffic in all weather.

Construction layers (bottom to top):

  1. Subgrade: The natural ground, cleared and shaped. Remove topsoil and organic material — it holds water and rots.
  2. Base course: Large stones (10-20 cm) laid on the subgrade. This is the foundation. 15-20 cm thick.
  3. Surface course: Smaller gravel (2-5 cm) packed over the base. 10-15 cm thick.
  4. Wearing course (optional): Fine gravel or crushed stone dust on top. Fills the gaps between larger stones and creates a smooth surface. 3-5 cm thick.

Width: Minimum 3 m for one-way traffic with passing places. 4-5 m for two-way. At passing places (every 200-300 m on narrow roads), widen to 5-6 m.

Time investment: A crew of 10 with hand tools builds about 50-100 m of gravel road per day, depending on material distance and terrain.

Corduroy Road

Logs laid side by side across the road direction, creating a solid surface over swampy or soft ground where other road types sink.

Construction:

  1. Lay logs (15-25 cm diameter, 3-4 m long) perpendicular to the direction of travel
  2. Pack them tightly — gaps cause wheels to drop and break
  3. Pin logs in place with stakes driven alongside
  4. Cover with a layer of soil, sand, or gravel to create a smoother surface
  5. Edge logs on both sides prevent the surface logs from spreading

Limitations: Rough ride. Logs rot in 3-5 years and need replacement. The surface heaves as logs decay unevenly. Use corduroy only where other options are impossible — it’s labor-intensive and temporary.

Cobblestone & Paved Roads

For high-traffic areas (settlement center, market square, approach to a bridge), cobblestone provides a permanent surface.

Construction:

  1. Excavate the roadbed 25-30 cm deep
  2. Lay a base of coarse gravel or crushed stone, 15 cm thick, compacted
  3. Spread a setting bed of sand, 5-8 cm thick, leveled
  4. Set cobblestones (rounded river stones, 10-15 cm diameter) into the sand bed, tapping each one level with a mallet
  5. Fill joints between stones with sand, swept in and wetted to settle
  6. The crown of the road should be 3-5 cm higher at the center than the edges

Cobblestone is permanent, supports heavy loads, and requires minimal maintenance. The drawback: it’s extremely labor-intensive. A skilled crew lays about 10-15 square meters per day.

Drainage Systems

Road Crown & Camber

Every road surface must be higher in the center than at the edges. This is called crown or camber. Water flows to the sides instead of pooling on the surface.

  • Target crown: 2-4% slope from center to edge. For a 4 m wide road, the center is 4-8 cm higher than the edges.
  • On hillside roads: Slope the entire surface toward the downhill ditch. Don’t crown — you want all water going one direction.
  • Maintain the crown every time you grade or add material. A road that loses its crown deteriorates fast.

Side Ditches

Ditches run along both sides of the road, collecting water from the crown and carrying it away.

  • Dimensions: 30-50 cm deep, 50-80 cm wide, V-shaped or trapezoidal
  • Grade: Ditches must slope toward an outlet (stream, low ground, drainage pond). Minimum 1% slope to keep water moving.
  • Keep them clear. A clogged ditch is useless. Inspect after every heavy rain.
  • On flat ground: You may need to dig the ditches deeper or create an artificial outlet

Culverts & Cross-Drains

Where a stream or drainage path crosses the road, the water must pass underneath through a culvert.

Simple culvert construction:

  1. Dig a trench across the roadbed, deep enough for the pipe or channel plus 30 cm of cover
  2. Pipe options: Salvaged concrete or steel pipe (best), a hollow log, a stone-lined channel with flat stone cap, or even lashed-together poles covered with clay
  3. Lay the culvert on a bed of gravel. Slope it slightly (1-2%) to prevent silting.
  4. Backfill over the culvert with gravel, then road surface material
  5. Stone or brush the inlet and outlet to prevent erosion

Sizing: The culvert must handle peak flow. A rule of thumb: the culvert opening should be at least as large as the natural channel it replaces. When in doubt, go bigger. An undersized culvert causes the road to wash out.

Grading & Earthwork

Essential Tools

Road building with hand tools requires:

  • Shovels: Round-point for digging, square-point for grading
  • Picks and mattocks: Breaking hard ground and roots
  • Rakes: Spreading gravel and leveling
  • Hand tampers: Compacting the surface (a flat plate on a long handle)
  • Wheelbarrows or carts: Moving material
  • String and stakes: Setting grade and alignment
  • Water level: A clear tube filled with water for establishing level over distance

Cut & Fill Technique

On hillsides, you must create a level roadbed by cutting into the uphill side and filling the downhill side.

  1. Set stakes along the desired road centerline
  2. From the centerline, measure half the road width in both directions
  3. On the uphill side, cut into the slope — the material you remove becomes fill
  4. On the downhill side, build up with the cut material, compacting in layers
  5. The cut face (uphill bank) should be sloped back, not vertical, to prevent collapse. Slope: 1.5:1 (horizontal:vertical) for most soils, steeper for rock.
  6. Build a retaining wall or place large stones at the base of the fill if the slope is steep

Critical rule: Never build on uncompacted fill. Layers of loose soil will settle and create ruts. Compact every 15-20 cm layer before adding the next.

Compaction Methods

  • Hand tamping: A flat plate (30 × 30 cm) on a handle, lifted and dropped. Slow but effective.
  • Animal-drawn roller: A heavy log or stone cylinder pulled by oxen or horses. Much faster than hand tamping.
  • Water settlement: Flood the surface with water and let it percolate through. Repeat several times. This settles the material naturally but takes days.
  • Traffic compaction: Let people and animals walk on the new surface for a few days before allowing heavy cart traffic.

Road Maintenance

Seasonal Maintenance Schedule

Spring (after thaw/rainy season):

  • Walk every road. Note washouts, potholes, ditch blockages, and culvert damage.
  • Clear all ditches and culvert inlets.
  • Fill potholes and ruts with gravel. Compact.
  • Regrade any sections that have lost their crown.

Summer:

  • Dust control: sprinkle water in dry periods to prevent surface erosion by wind.
  • Cut vegetation encroaching from the sides.
  • Best time for major construction projects (dry ground is easier to work).

Fall:

  • Pre-winter inspection. Fix everything before the ground freezes.
  • Ensure all drainage is clear for winter rains/snowmelt.
  • Stock gravel piles at problem areas for spring repairs.

Labor allocation: Road maintenance is community work. Historically, most societies required every able-bodied person to contribute several days per year to road work (corvée labor). A community of 30 people contributing 5 days each per year provides 150 person-days of road maintenance — enough to keep 5-10 km of gravel road in good condition.

Pothole & Washout Repair

Potholes:

  1. Dig out the pothole to sound material — don’t just fill over a soft base
  2. Fill with gravel in layers, compacting each
  3. Crown the patch slightly above the surrounding surface — it will compact down

Washouts:

  1. A washout means drainage failed. Find and fix the drainage problem first.
  2. Rebuild the road cross-section from the base up
  3. Install or enlarge culverts if water is overtopping the road
  4. Consider rerouting the road if the location is inherently problematic (natural drainage path, flood-prone area)

Road priority: Not all roads deserve equal investment. Focus maintenance and improvement on:

  1. Routes to water sources
  2. Routes to agricultural land
  3. Routes connecting your settlement to trade partners
  4. Internal settlement roads

A community with one excellent road to its water source and fields is better served than one with four mediocre roads going in every direction.