Trail Care Crew
Mtn Bike Patrol
Save the Trails!
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
B. Flagging the trail
- 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..
- When flagging trees, place the knot on the side that you want the tread to
- Place flags close together. You cannot over flag a chosen route. Flag any
turns extremely well to prevent misalignment.
- 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.
- 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
- 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.
- When trimming branches, always trim at the trunk or branch junction to
- If necessary, stake the center-line where you want the tread to be placed.
D. Constructing the tread
- 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.
- 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.
- 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.
- 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.
- Bridges should be strong enough to hold the heaviest intended user
(bike, horse, ATV).
- Bridges can be constructed of different materials: wood, metal, stone,
- Use screws - not nails.
- Extend ramps into the ground.
- If trees from the site are used, don't use hardwoods or pines. (Cedars,
hemlocks, locust, redwoods, or cypress are all good.)
- Bark must be stripped or wood will rot and be susceptible to bugs.
- 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
- 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).
- 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
- 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
- The upper leg should be insloped, moving into a large flat turning
platform, then returned to the normal outslope on the lower leg.
- 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.
- 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
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