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Trailbuilding Basics

Chapter 4 - Construction

A. Knowing the grade

Use a clinometer to keep the trail to a 10% overall grade. This will allow short changes in grade to avoid obstacles yet remain at a maintainable grade overall. Designing grade dips into the trail will break up long, straight linear runs, keep speeds slower naturally, and divert any runoff that might find its way down the trail.

clinometer clinometer
Clinometers

B. Flagging the trail

  1. Now that you have established the control points, users and grade, start flagging the trail. Choose your flagging color carefully. Red, yellow, and orange don't work well during the fall season in areas where hardwoods grow, and green may not be visible during the summer. Fluorescent blue or pink work best year round. Check with your local land manager to make sure they are not already using the color you intend to use for other, unrelated projects..

  2. When flagging trees, place the knot on the side that you want the tread to fall on.

  3. Place flags close together. You cannot over flag a chosen route. Flag any turns extremely well to prevent misalignment.

  4. If more than one group will be working to build the trail, then flag the trail corridor, as opposed to just flagging the center line.

  5. When flagging the route, go through and spot flags every 50 feet or so, making sure that you can see from flag to flag. Then walk the route backwards, making adjustments to improve the flow. After you return to the beginning, walk the route again, and fill in the gaps between the spot flagging by placing more flagging about every 10 feet. This will help define the actual line that the trail is to follow. Once again walk (or run if you can) the entire flag line in both directions, making small adjustments to improve flow.

C. Clearing the trail corridor

digging them out, roots and all

  1. Clear vegetation three feet on either side of tread. Leave grasses and established trees (get approval on what size trees to cut). Completely remove all saplings, briars, vines and other fast-growing impediments by digging them out, roots and all. Do not cut woody plants off at ground level.

  2. When trimming branches, always trim at the trunk or branch junction to prevent rot.

  3. If necessary, stake the center-line where you want the tread to be placed.

Pulaski McLeod
Pulaski McLeod

D. Constructing the tread

Bench cut

  1. Bench cut construction

    Full bench: (Click here for a full bench cut diagram) It is best to dig down to mineral soil for the entire width of the tread. This will result in a trail with a stable tread. It will last longer and require less maintenance.

    Partial bench: This type consists of a partial fillslope and partial bench cut. This usually results in tread creep caused by the loose soil being pushed down the side of the hill during use. This type of construction may also result in a berm that will block water flow across the tread.

  2. Blending the back-cut into the backslope will prevent water from falling off the backslope onto the trail. Falling water would cause undercutting or a trench in the trail tread.

  3. Outsloping is the most important part of the tread. Water will not flow across the tread without proper outslope. The finished the tread should have a 3%-5% outslope from the back of the tread to the outer edge. This can be measured using a digital level or a piece of wood (or cardboard) cut into a triangle and premeasured for the proper outslope. When using the latter method the narrow end should be placed at the inside edge of the trail while making adjustments to the tread outslope until the top edge of the triangle is level.

  4. Know who will be the primary users of the trail. For more technical rides, leave in natural obstacles (rock, roots) that are not a safety hazard and will not contribute to erosion. For advanced trails, put in longer sustained climbs and more difficult technical features.

E. Bridges

  1. Bridges should be strong enough to hold the heaviest intended user (bike, horse, ATV).

    Bridges

  2. Bridges can be constructed of different materials: wood, metal, stone, plastic.

  3. Use screws - not nails.

  4. Extend ramps into the ground.

  5. If trees from the site are used, don't use hardwoods or pines. (Cedars, hemlocks, locust, redwoods, or cypress are all good.)

  6. Bark must be stripped or wood will rot and be susceptible to bugs.

  7. If rails are required and the bridge is located just before or after a turn, the rail on inside edge should be shortened to accommodate riders leaning into the turn.

F. Switchbacks

  1. A switchback is a structure that makes a level turn throughout the transition, and then is routed in a new direction (Click here for a full switchback diagram).

    Key features:

    • Drainage runs off the back of the turn
    • Flat table (the turn) forces the trail to cross the fall line of the hill. Users are turning on a level platform. The trail stays on the contour in both directions.
    • Split the difference between cutting down and building a crib wall. Use material excavated from the top leg to build up the bottom leg behind the crib wall.

  2. The upper leg should be insloped, moving into a large flat turning platform, then returned to the normal outslope on the lower leg.

  3. Most turns that are described as switchbacks are not actually switchbacks. They are climbing turns (Click here for a full climbing turn diagram). A climbing turn is a turn that climbs (or descends) the existing grade of the hill to make a steep, tight turn.

  4. Climbing turns should be used on slopes less than 7% grade and have at least 75 feet between the upper leg and the lower leg (where the turn begins and ends).


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