Introduction: Tree Trunk Retaining Wall
We recently had a tired bay laurel tree cut down on our steep upslope garden to allow more sunlight in. The thought and expense of carting off the huge amount of timber, from the treeto a landfill seemed like a huge waste of time energy and money. So I came up with the idea of building a retaining wall, and creating a flat area from the logs. We had a professional cut the tree down and strip the trunk and branches of small limbs, anything larger than 3” in diameter was saved for future use in the garden. The small stuff was chipped for mulch in our front yard. Judging by some bay laurel logs that have been left out in our garden, I believe this wall should last 15 to 20 years. Your mileage may vary depending on the species of tree.
Electric Jack Hammer (I bought an import one from Amazon for about $225.00)
Picks and shovels
Peavey (for moving logs) optional
2 ton chain come-along (skip the wire rope come-alongs, I destroyed 2 of them on this project).
Chain or wire rope (to use as slings for the logs)
Powerful electric drill with a 3/4'’x18” wood auger bit
5/8 rebar, I used about 10 pieces at 1.5’ and 10 at 2’ (to spike the wall together)
Roll of drain board (to keep water pressure from pushing your wall over)
4” perforated drain pipe
Crushed drain rock (to backfill around the pipe)
Landscape cloth (to wrap around the pipe and crushed rock).
Step 1: Start Building Your Wall
After your tree is cut down take stock of the materials you have. The largest pieces will be your base, run the base trunks around the perimeter of your wall, try to keep it close to level, excavating as necessary. My base trunks are wedged against the old bay laurel stump, which has since sprouted and become a hedge in front of the wall. So I’m not worried about any movement. Moving the larger logs into position was a challenge, my main tree trunk measured 14' long and 3’ in diameter at the base. I’m lucky to have spent a part of my youth working with an old ship captain (Ken Reynard former curator at the San Diego maritime museum) who restored the ship Star of India of 1863. He had lots of ideas about how to move large stuff, one that comes to mind was towing the Star of India with his Volkswagen bug, that must have been a sight to see. I learned about levers, fulcrums, chain falls com- alongs and a host of other ways to apply elbow grease. I had a convenient oak tree just up the hill that I used as a deadman (basically a ground anchor). I wrapped a chain around it and hooked my come-along to that so I could pull and lever the logs into position. Please be extremely careful when maneuvering things this heavy. It only takes one slip or mistake to ruin your back forever.
Once the base trunks are laid start laying more logs on top, try to avoid lining the joints up, the more you span the joints. The stronger the wall will be. Spike each log to the log below by drilling 18” deep ¾” holes on 3’ centers. Remove the bit from the jackhammer and use the jackhammer to drive the 5/8” rebar through the holes you have drilled. It takes a little fiddling to get the jackhammer started but it will drive the spikes home even after they have reached the bottom of the hole. Bend the top of the rebar over with a sledge hammer if any is left proud (sticking out).
Keep adding logs until you have reached the desired height. Or in my case run out of logs. The height of my wall is about 3 feet.
Step 2: Drainage and Backfill
Once your wall is done. Lay your landscape cloth along the base of the wall so that the center is approximately where the wall meets the ground. Then lay a small amount of crushed rock on top of the fabric. Lay your pipe on top of the gravel and use the gravel to give the pipe about ¼” per foot slope to the exit point. Then roll out your drain board and tack it to the wall let the bottom of the drain board touch the gravel that’s holding the pipe, you may have to trim the bottom of the drain board, add more gravel to cover the top of the pipe. Then wrap the loose landscape cloth around the gravel. Carefully start backfilling your wall, making sure your cloth stays in position, digging dirt out of the hillside as you go. We used a layer of landscape cloth on top of the flat area and then covered this with 3” of decorative gravel.