Set in Stone

A WELL-BUILT GABION WALL IS TIME­LESS AND CAN WITH­STAND EARTH’S NAT­U­RAL FORCES

Modern Pioneer - - Contents - By Clay New­comb

A well-built gabion wall is time­less and can with­stand earth’s nat­u­ral forces

In the grand scheme of hu­man his­tory, us­ing ter­races to level sloped land is a tech­nol­ogy com­pa­ra­ble to har­ness­ing the power of fire. Much of the earth’s sur­face is sloped, mak­ing it dif­fi­cult to use. The more pop­u­lated the earth has be­come, the more hu­mans have had to make use of the land they’ve got.

Build­ing a re­tain­ing wall to re­duce a slope is an an­cient skill. You’ll need to un­der­stand some ba­sic physics, drainage and soil­move­ment pat­terns to build a wall that will last a life­time. You’ll also need to be­come fa­mil­iar with the ma­te­ri­als and build­ing struc­tures used to cre­ate the unique, strong and beau­ti­ful gabion walls we’ll dis­cuss in this ar­ti­cle.

What’s a Gabion?

Gabions are rock-filled wire bas­kets. The word “gabion” (root gab­bione) is an Ital­ian word mean­ing “big cage.” In my opin­ion, they’re faster to build and less la­bo­ri­ous than many other wall types. They’re cheaper than con­crete land­scape-block walls, and they’re cheaper than a dry-stack stone wall, if the stone is pur­chased at re­tail price.

Gath­er­ing stone your­self is prob­a­bly the cheap­est wall-build­ing method. Rail­road-tie walls are cheap, but they’re la­bor-in­ten­sive and only have a 20-year life­span. How­ever, in build­ing a gabion, you don’t have to lift heavy blocks, rocks or tim­bers by hand—with the right equip­ment. If built cor­rectly, a gabion wall will last a life­time. Most of the hand-la­bor is in con­struct­ing the wire bas­kets. A trac­tor with a bucket loader is im­por­tant for eas­ily putting the rocks into the bas­kets.

“Keep the seg­ments of the wall small so the bas­kets main­tain a rigid struc­ture to con­tain the rocks.”

Is a Gabion Wall Right for You?

I chose to build gabion walls around my home based upon three con­sid­er­a­tions: aes­thet­ics, fi­nances and ease of con­struc­tion. Gabion walls have a unique and com­plex vis­ual appeal. The man­made-grid look of the wire con­trasts with the nat­u­ral shapes

of the rock, cre­at­ing a mod­ern, yet rus­tic look. A gabion wall at your home will set you apart be­cause they aren’t of­ten used in res­i­den­tial ap­pli­ca­tions. How­ever, I find them very prac­ti­cal and eas­ier to build than many al­ter­na­tives. The ma­te­ri­als are read­ily avail­able and in­ex­pen­sive.

I’ve built mul­ti­ple types of re­tain­ing walls us­ing all types of ma­te­ri­als, in­clud­ing gabions, nat­u­ral stone, rail­road ties and con­crete land­scape blocks. In the Ozarks of Arkansas, where I live, re­tain­ing walls are very com­mon. I spent eight years in the pro­fes­sional land­scap­ing busi­ness, and one of my main du­ties was build­ing re­tain­ing walls. I’ve had the ex­pe­ri­ence of see­ing walls I’ve built main­tain their in­tegrity for more than a decade. Fu­ture decades will con­tinue to tell my story, pass or fail, in Ozark wall build­ing.

“Many road de­part­ments use gabion walls along in­ter­states and road­ways.”

The Beefier, the Bet­ter

I’m amazed by how many walls don’t last. In my opin­ion, you can’t “over­build” a re­tain­ing wall. The static pres­sure ex­erted by soil on walls over long pe­ri­ods of time is amaz­ingly strong and dif­fi­cult to un­der­stand. Soil moves, grav­ity pulls ev­ery­thing down­ward, and the weight and the earth’s strength push­ing on a wall is sig­nif­i­cant, even if the wall is only a few feet tall. It’s even more sig­nif­i­cant if the wall is 3 to 5 feet tall.

If not done cor­rectly, a wall will slope for­ward within a few years and be face-first on the ground within a few decades. How­ever, gabion walls are unique and com­pletely por­ous, al­low­ing wa­ter to freely flow through, which di­min­ishes the pres­sure on the wall. Wa­ter-logged soil is ex­tremely heavy, and by giv­ing the wa­ter an exit path, pres­sure is re­leased. No drains are needed on gabion walls; the wall is the drain.

Ma­te­ri­als Needed

For my gabions, I chose 4x4-inch grid live­stock panel pur­chased from the lo­cal farm store. These pan­els are 16 feet long and 4 feet tall, and are read­ily avail­able across the coun­try. I paid ap­prox­i­mately $30 per panel. How­ever, there are many op­tions for types of wire. What­ever you choose, it must be strong enough to sup­port its own weight and that of the rocks. Choose your grid size based upon the size of rocks you’ll be us­ing. If you’ve got big rocks, then you can have big­ger grids. Wire

with big­ger holes is usu­ally cheaper. You’ll need a pair of bolt cut­ters to cut the wire.

Se­condly, you’ll need some heavy-duty gal­va­nized wire that won’t rust. The wire is very im­por­tant be­cause it holds the bas­ket to­gether. Don’t skimp on wire; buy more than you think you’ll need. You’ll also need some good pli­ers, dykes or wire cut­ters. If you build a large wall, your hands will be worn out from all the cut­ting. I rec­om­mend spend­ing an ex­tra $10 on qual­ity pli­ers.

The third ma­te­rial needed is the rock. Ev­ery re­gion of the coun­try has lo­cal gravel and rock sup­plies read­ily avail­able. I used over­sized river gravel na­tive to the Ozarks, pri­mar­ily be­cause of its look and color. How­ever, it would have been eas­ier and cheaper to use big­ger, chunkier rock.

Most re­gions of the coun­try have quar­ries that pro­duce over­sized gravel 4 to 6 inches in di­am­e­ter. Many road de­part­ments use gabion walls along in­ter­states and road­ways. They typ­i­cally use the most in­ex­pen­sive rock type, so take note of the ma­te­ri­als they use for your own project.

Con­struct­ing the Walls

In my ex­pe­ri­ence, this type of gabion is ad­e­quate for walls less than 4 feet tall. I per­son­ally wouldn’t build one any taller. There’s no need for a foun­da­tion or for bury­ing the base of the wall into the ground. Strength isn’t gained, be­cause the wall isn’t rigid. A crit­i­cal ac­tion, how­ever, is to cre­ate level sur­faces on which to place the wire bas­kets. The top of the wall will only be as level as the ground un­der­neath it. Use a string level, tran­sit or even a long level.

Build­ing the bas­kets is sim­ple. Mea­sure the wall di­men­sions and use a bolt cut­ter to cre­ate the sides of the bas­kets. Then, use gal­va­nized wire to join the sides. Put sec­tions of live­stock panel ev­ery 4 feet or so that run per­pen­dic­u­lar to the face of the wall. These strengthen the wall.

An­other crit­i­cal con­struc­tion as­pect is us­ing tee posts as dead­men. In wall build­ing, the term “dead­man” refers to a hor­i­zon­tal struc­ture that goes back into the bank, hold­ing the wall and soil bank to­gether. When build­ing a dry-stack wall, you use long rocks that sink

back into the bank. For gabions, I use tee posts. I ham­mer in the tee posts, and then wire them to the bas­kets. The tee posts are also held in place by the gravel sur­round­ing them. Place a tee post about ev­ery 5 feet. In shorter walls, you can ham­mer the tee post straight down in the cen­ter of the bas­kets and sur­round them with gravel. These dead­men are crit­i­cal to hold the bas­kets in place when pour­ing in rocks.

Keep the seg­ments of the wall small so the bas­kets main­tain a rigid struc­ture to con­tain the rocks. If you have a 16-foot wall, you’ll need to place a di­vider about ev­ery 4 feet. Dif­fer­ent types of wire will re­quire dif­fer­ent spac­ing. The idea is that the bas­ket will have enough sup­port to main­tain its shape with­out bulging. I used sec­tions of live­stock panel to cre­ate the di­viders. In be­tween the di­viders (ev­ery 2 feet), I put a wire jumper to keep the mid­dle sec­tions from bulging. For di­men­sions, I made my smaller wall 2 feet high by 16 inches wide. My larger wall is about 3 feet high and 20 inches wide. The taller the wall, the wider I like to con­struct it.

Add the Rocks

Once the bas­kets are set, level and sturdy, you can be­gin pour­ing in the rocks. The dead­men must be se­cured to the bas­kets, be­cause they’ll be the only sup­port (don’t back­fill with dirt un­til the wall is com­plete). If the bas­kets aren’t an­chored, the weight of the rocks will push the bas­kets. Use a trac­tor (con­sider rent­ing one if you don’t own one) with a bucket to pour in the rocks. On my wall, I poured in sec­tions of about 6 to 10 inches deep, then hand-fit the outer rocks so they looked good. Of course, this takes time and is op­tional. Once the bas­kets are filled with rocks, you can back­fill dirt be­hind the wall. Done!

(be­low, left) Use a pair of bolt cut­ters to cut the wire into the sec­tions you’ll need to cre­ate ap­pro­pri­ately sized bas­kets.

(be­low, right) Use gal­va­nized wire to build topless and bot­tom­less wire bas­kets. Don’t be afraid to use a lot. The bas­kets get their strength from the wire.

(op­po­site) You don’t have to build the bas­kets in place. You can build them where it’s com­fort­able, then set them in place when fin­ished. PHO­TOS BY CLAY NEW­COMB

(above) Be sure to level the ground be­neath the walls. There’s no need for a foot­ing or to place the base of the wall un­der­ground. (be­low) The au­thor uses tee posts as dead­men. These sup­port struc­tures are both in the wall and in the bank. They should be wired se­curely to the bas­kets. They also keep the bas­kets in place when you’re fill­ing them with rocks.

PHO­TOS BY CLAY NEW­COMB

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