Standards and Procedures:
Locust Log Work General Principles
Rock is the most long-lasting building material for trail work, but as a general rule, we cannot harvest rock from outside the trail corridor in the Pisgah Ranger District unless approved by a NEPA survey. And in many areas of the district, suitably large rock simply isn’t present. Black locust timber fills this gap and enables us to build stable, long lasting structures where they are needed to repair or stabilize existing trails.
Black locust is an incredibly strong and rot-resistant wood, native to the region, that easily lasts decades even when set in the ground and exposed to the elements. Because other types of native wood don’t even come close to the durability of black locust, this tree should be viewed as a precious resource. The tree thrives in open areas and doesn’t tolerate shade well, so its rate of regeneration within the forested Pisgah Ranger District is slow. Anything built with locust should be well-justified and constructed to the highest quality to maximize the use we get out of this resource.
In addition, building any structure requires a significant investment of time and logistics, so consider whether a section truly requires a structure, or if the problem could be mitigated by drainage or tread improvements. Keep in mind that structures are not a fix for poor drainage management, and drainage should be incorporated into the design of structures. In certain longer trail sections that are severely degraded, it may be worth exploring the option to relocate rather than attempting to mitigate with structures.
When building with locust is the right choice, the key is to make structures as solid and sustainable as possible. This document will outline general key points for good log construction, and will link to more detailed guides on specific structures.
Key Points:
- Peeling logs
- Create a strong foundation
- Create strong joints
- Cutting notches
- Use rock to fill
- Choose sustainable structure designs
See Also:
- Summary/Takeaways
- Tools and PPE Guidelines
- Gallery
Peeling Logs
Standards:
- All logs should have the bark removed prior to construction. This is a simple but often neglected step which extends the life of a log structure.
- Leaving the bark on traps moisture and provides a habitat for invertebrates and fungi that speed up the rotting process.
Procedures:
- Using a draw knife is generally the most straightforward way to remove bark, but an axe or pulaski can work as well. Even a shovel can be used to pry bark loose. Bark spuds, though less common, can work well on freshly fallen trees.
- Remove as much of the bark as possible, down to the actual wood.
- Avoid leaving a huge pile of bark peelings at the work site as this can be unsightly. Scatter bark or rake the peelings out of the main trail area, consider covering with leaf litter.
Several layers of bark are visible in this partially peeled locust log. Try to remove them all, leaving just the solid wood which will not trap and hold water and decomposing organisms.
Layout, Prep, and Building a Strong Foundation
Standards:
- A strong foundation is essential for keeping structures stable over the long term.
- The foundation of the structure isn’t only physical - it also involves thinking and planning the best layout.
- Lay logs in a way that suits the terrain and takes advantages of curvature in the logs, adapting to curves in the trail and avoiding gaps underneath logs.
- The best way to keep the foundation strong is to bury the bottom layer of your structure and fill with rock/gravel, tamping to lock everything in place.
- Pounding rebar through your structure into the ground can lend additional stability, but shouldn’t replace the need to base your structure solidly in the earth. Rebar will bend and shift over time if it’s the only thing holding the weight of your structure in place.
- Keeping your structure level, especially the foundation, is also important. A level structure will be more sound over time than one that’s off-kilter. Bring a level with you for that extra degree of quality. Remember, every minute you invest in getting it “just right” will pay dividends in quality over decades.
Procedures:
- Lay out logs before even making the first cuts. Determine which logs fit best in each place. Can you adapt a curved log to match a natural curve in the terrain? Rotate logs to investigate which orientation gives the best results and mark the top for reference.
- Spend the extra time to come up with a good initial plan and visualize how your material will come together. Remember the mantra: “Measure twice, cut once.”
- Check for level frequently, and dig as much as necessary to adjust your foundation and make it level and stable.
- For staircases, bury your bottom step in the ground and pack it in with crushed rock. This will pay off in the long term as your entire structure is anchored and the possibility of undercutting is much reduced.
- In the same way, bury the bottom tier of log cribbing. The more you can anchor log structures into the ground with their own weight, the better.
- Frequently take a step back and look at your evolving structure from a distance.
Creating Strong Joints
Standards:
- Miter joints are strong, aesthetically pleasing, and simple to make with a chainsaw. For these reasons they are preferable whenever possible.
- For best results, physically attach jointed logs together using 8-12” long ⅜” landscape spikes. This will require a powerful drill with a ⅜” auger bit to drill pilot holes and a single-jack sledge hammer to pound spikes into place.
- Relying on rebar or locust stakes alone to hold individual logs in place is unreliable over time. Structures that are spiked together have much greater structural integrity. As an added benefit, spikes are more cost-efficient than rebar.
Procedures:
- To miter join logs at an angle, lay one long on top of the other at the intended angle, hold the top log so it matches the level with the bottom log, and simply make one cut through both logs.
- Spend the extra 5 minutes to get your miter joint as tight as possible by making a second cut straight down the kerf of the joint. A sharp chain makes this much more effective, so bringing an extra sharpened chain is a good idea.
- It’s important to have a second person to help secure logs while making miter cuts, drilling holes, etc. Make sure the second person has appropriate PPE.
- Take advantage of the wedge-shaped end pieces left over after a cut. These can be wedged under logs to help keep them in place while making cuts.
- Spike joints from both sides, taking care not to drill into spikes that are already pounded in.
An example of two locust logs mitered together, forming a tight and elegant joint.
Cutting Notches
Standards:
- In cases where you need to connect two logs at perpendicular angles, notching will give you a stronger joint.
- Notching adds strength by allowing the logs to support most of their own weight, taking stress off of landscape spikes that are attaching them to one another.
Procedures:
- Cutting notches can be tricky and requires some practice.
- Take careful measurements of how wide the notch must be to accommodate the end of the other log.
- Using a chainsaw, lightly “feather” the bar back and forth over the section to be removed. Pause frequently to check the fit of the notch before continuing. If you remove too much material, you may end up with a loose notch that doesn’t provide as much stability.
- For even more stability, cut your notch and corresponding end log with matching, slightly sloped angles so that one slide into the other and wedges into place, unable to fall through completely.
Use Rock to Fill
Standards:
- Whether your structure is a staircase, a turnpike, or a crib wall, use rock as your primary fill, not soil.
- Filling with soil alone is likely to result in washed out structures, undercutting, and generally a less stable structure.
Any soil that does get used to top off gravel should be mineral soil, not organic.
Procedures:
- Crush rock on site or import gravel/ballast if logistically possible. Use the largest pieces to fill in along the edges to help prevent any fill from washing out from underneath. Layer smaller gravel on top.
- Pound/tamp crushed rock to lock everything in tightly.
- Top off the fill with a layer of mineral soil at the end.
Filling each step landing with crushed stone provides a hardened tread surface that doesn’t wash out. Eventually these landings will be topped with a layer of mineral soil.
Choose Sustainable Structure Designs
When building with native timber, strive to follow best practices and build to the highest quality possible. Below are links to pages with guidlines of building specific log structures, along with some photos. You can also find these pages on the Trail Academy's main dropdown menu.
- Log ladder staircase
- Log crib walls
- Log water bars
- Log Turnpike
- Log box steps
- Log check steps
Summary / Takeaways
Good Log Construction:
- Black locust logs
- Peeled Logs
- Foundation embedded in the ground
- Level from side to side
- Logs tightly joined and spiked
-Logs notched together when appropriate
- Rock/gravel used for fill
- No gaps under logs
Poor Log Construction:
- Off-kilter from side to side
- Bark left on
- Gaps between or underneath logs
- Weak foundation, sits on top of ground.
- Filled with soil only
- Logs not joined, reliant on stakes or rebar which can shift
Tool and PPE Guidelines
Tools for Log Work:
- Chainsaw with a sharpened chain
- Extra sharpened chains for easy replacement
- Draw Knife - for peeling bark. Axe, pulaski, bark spud, spade shovel can all serve the same purpose of a draw knife if one is unavailable
- Straps or Log Tongs - useful for dragging/carrying logs from place to place
- Peavy or Cant Hook - useful for rolling and manipulating very large, heavy logs (for example in bridge work).
- Power drill - strong enough to drill through locust, can be battery powered, gas powered, or electric with a generator. Be sure to bring extra fuel/batteries.
- ⅜” Auger drill bit - for best results, test your drill and bit in locust before trekking out to a project site.
- ⅜” Landscape spikes - More economical than rebar and provides a tighter joint. Be sure to choose spikes that are long enough for the locust you are using. 8” to 12” is a typical size range.
- Lumber Crayon - or marker, etc. is extremely helpful for making accurate cuts and measurements.
- Level - important for making sure foundation and step surfaces are level from side to side.
- Single-jack sledgehammer - used for pounding spikes into wood, as well as packing gravel fill tightly into place.
- Pick Mattock, or digging tools of choice - Pick mattock is great for heavy digging, which is likely needed to properly bury and entrench logs in place. Other tools, like hoes or pulaskis, can also work.
- Rapid digger, mini-pick, prospector's pick - smaller tool useful for digging in tight quarters is very helpful for digging small adjustments around logs.
- Pulaski and/or loppers - for removing roots that get in the way of setting logs.
- Buckets or canvas rock bags - used to transport gravel and soil from place to place.
- Shovel - useful for removing soil, filling bags, shaping holes, etc.
PPE for Log Work:
- All regular PPE - including hard hat, gloves, eye protection, boots, and long pants
- All Chainsaw PPE - including chaps, ear protection and the above standard PPE. In addition to the sawyer, whoever is assisting the sawyer with holding logs in place should be wearing ear protection as well.
- USFS Chainsaw training and certification is required to operate a chainsaw on the Pisgah Ranger District.
Gallery
Unique structure built on Avery Creek trail combines tiered locust cribbing, turnpiking, and a simple foot bridge to shore up a messy area with year round water flow.
Log Ladder Steps installed on Barnett Branch have weathered nicely and integrate well with the landscape.
Locust log turnpike constructed on a boggy section of Bennett Gap is an elegant and sustainable solution in areas where establishing drainage is difficult.