Build a Log Bridge

Here is a minimally disruptive method of building a log bridge across a stream.


| February/March 1994



142 log bridge - photo 5 - planks

The finished log bridge looked like this. The 2 x 12 boards running the length of the bridge provide a track for car or tractor tires.

PHOTO: MOTHER EARTH NEWS STAFF

Outside of a drought or miracle similar to the crossing of the Red Sea, there is no way to make a dry crossing over a body of water without a bridge. I desperately needed one to cross the Class One stream on our property in the western Cascades of Oregon. So I decided to build a log bridge, one that would meet my needs without causing damage to the environment.

The first thing I did was take a trip to the area State Forest office and make a request for a bridge-building permit. That was followed by an on-site inspection by the local forester, who decided the stream banks were level enough so that water drainage from a road wouldn't flow down onto a bridge and into the stream.

The permit explained the two best methods of moving logs across a stream without harming the stream bed. The method I selected, explained below, involves an elevated-cable system, a truck winch, and an anchored-log tripod with a cable pulley. This allowed me to haul logs across the stream without touching the stream bed at all.

The other (more costly) method is to use a large backhoe to lift the logs across the stream. According to the permit, we were also responsible for reseeding those areas along the roadway and bridge that were disrupted by our machinery. The whole process was so simple and turned out so well that I drew up some plans and diagrams to share with you.

Bridge Construction

Begin by finding (or, if necessary, hiring) someone with a portable saw mill to saw planks for the bridge deck. We had a friend cut forty 3 x 12s, sixteen 2 x 12s, and seven 4 x 6s. Cut down and limb just enough cedar trees to make six 42' span logs (which run across the stream) and two 12' bunker logs (which hold up the span logs).

Place the larger of the two bunker logs in a shallow trench on the accessible side of the stream (the side you're standing on); you may have to dig a trench if a natural one doesn't exist. Level the top. Next, position long but narrow logs across the stream, allowing the top ends to rest on the bunker so that they form a ramp. Using the ramp, roll the second bunker log to the far bank.





mother earth news fair

MOTHER EARTH NEWS FAIR

Feb. 17-18, 2018
Belton, Texas

More than 150 workshops, great deals from more than 200 exhibitors, off-stage demos, hands-on workshops, and great food!

LEARN MORE