How to build a retaining wall. An easy rock wall or a rock garden?

This project is for the homeowner with small retaining wall problems, lots of rock, and not enough yard space. This is no way an engineered wall! But low or well built walls can easily survive for 50 to 100 years with a little thought. Just make sure you reinforce them properly if people are going to be walking above them or they are holding up something important like your house!

Look at the height of the wall. If it's greater than 4 foot and you can't push back another 4-8 feet to make the next wall, or the combined height is more maybe 20 feet, than you'll probably have to have an engineered reinforced concrete wall built. (Some communities limit you to as low as 2 feet, but usually it's 3 or 4 feet in height.) Length of wall doesn't matter. The wall can be 500 feet long with 500 feet of muddy soil behind it, if the shelves are wide, it is only the height that matters. I personally like to limit the height of each wall to bench height, about two feet. It's safer, much more fun to garden in, and has it's own seating.

Wire and cement at least the base of the rock wall if you need a long term wall!

I'll usually make the bottom wall rock with cement and wire, a lot of wire. Chicken wire, non-climb fence wire, barbed wire, rebar, or old metal fence posts. Basically any wire or metal fencing laying around goes behind the rock in mortar as you construct the wall. The big rocks go on the bottom. I like to use a dolly to roll over the 300 pounders to dig into the bottom of the slope.

Leave about 4 inches behind the rocks to stuff the wire in. If you want a better wall, buy some welded wire and actually clean out a 'ditch' along the bottom of the slope, fill it with 3 inches of mortar, place the wire into it and roll your base rocks carefully in place to make your bottom 'footing'. This makes your rock wall into a 50 year wall. Without this simple footing the rocks have a tendency to move. This footing is similar to a concrete retaining wall, just not as 'engineered'. The wide base needs to go back into the slope at least half as wide as the wall is tall. In other words, for a four foot wall, two feet wide.

Use the same basic structure of a rock wall for a foundation covering  'rock wall'. If the concrete or concrete block is to smooth, drive some concrete nails in so the cement has something to grab.

Plan for the wall drainage.

You should leave a few sloppy holes in your footing so the water can weep through and you'll have a place to plant some cool plants. You're building the opposite of a wall dam.

The pictured wall is new and almost 3 feet wide at the base, and only about 3 foot tall. Skinny walls are not very permanent.

The flower bed behind is filled with yarrow and hummingbird sage.

If you think a few of these rocks look square, you are right. This wall has a few pieces of concrete that we needed to get rid of in it. What better way to recycle!

This wall is about 30 years old, a little cracked, but still solid, again a wide wired base. Notice the vegetation covering it. (It's been in a greenhouse for years under constant irrigation.) This rock wall is home to many water loving plants including Wild Strawberry, Maidenhair fern, Red Lobelia and Columbine.

This wet rock wall is also inhabited by tree frogs and an occasional snake! It is real popular with the reptiles and amphibians in the summer.

Dry stack rock walls

Dry walls have a few loose rules.

Don't make them very high, 2 feet is good, 4 feet you need to be good. The better the rocks fit together, the wider the rocks, the more the wall is planted, the more stable the wall will be. Big rocks go on the bottom! Slope the wall in as it gets taller, 1-2 inches per foot of height is the minimum. A 4 foot wall made of round 4 inch rocks is a bad joke. If those are the rocks you have, buy some sheets of plywood, build a simple but strong form to support same and make a concrete 'rock' wall.

The plants in the rock wall to the right were planted about a year ago in the fall. They were watered a few times. They then survived the summer on no water with temperatures regularly exceeding 100 deg F. We had only 12 inches of rainfall that year! These plants include California fuchsia, a colorful perennial that attracts lots of hummingbirds. It can be planted directly into the wall or near the top where it can drape over a bit. Another plant in this dry wall is Dudlea sp. It is also very drought tolerant and lives naturally in rocky outcroppings. It is also a big hit with the hummingbirds. The gray fluffy looking thing is actually a sage. This creeping sage looks great at the top of walls as it cascades down and is only 6 inches to a foot tall. It is also deer proof.

If the rocks available are shale, very soft granite(you can easily break it with a hammer) or any other soft, porous rock, make a dry wall. A cement wall with this material will often fail, because the rocks will just break off and fall apart. But if your soil is a clay, this soft rock makes a great dry stack wall. Layer of rocks, fill in voids with loose, dry dirt, next layer of rock. Try to nest the rock in between the rocks of the lower layer. Water the wall as you finish each day or every time you walk away for a break. Dry stacks follow the same rules as a wired wall, but you are using clay instead of cement, and the wire only kinda works.

If you're retaining wall isn't really retaining anything important, just making life easier, maybe you should build a series of smaller dry rock walls(no mortar or concrete) and have fun planting yourself a rock garden in each one. Dry walls can be made of broken concrete, old tires(makes a great retaining wall to protect the 1964 Chevy pickup on blocks, behind the chicken coop) , logs(don't last long), concrete block (what's the point?), rocks, railroad ties (see logs) and almost anything else you can stack.

If your yard has rocks everywhere, great! Pick them up and make a rock wall, or place them next to each plant on the flat and call it a rock garden. If you live in Bakersfield, Los Angeles, or one of the other big cities with no rocks except by the pound from the local 'materials' company, look around for somebody removing some concrete. Broken concrete makes a great wall. It looks natural after you get a few plants growing into it.

Include a stair case. No big deal with rocks, just make smaller walls!

You can plant California fuchsia in the cracks. It doesn't mind being stepped on and it loves stairs and rock walls.

Anyone can build a rock wall.

If you're old, of small build, or fat and lazy, take longer and build a smaller wall. If you've got some big and strong help(for teenagers turn the TV, phone and computers off until the wall is done) build a wall with bigger rocks. Use tools! A little leverage goes a long way. And remember the big rocks go on the bottom so in most cases you don't have to lift them just roll them. Don't hurt your back. The wall does not need to be perfect! It's ok if it leans back here and there, the rocks look funny, not uniform, of different sizes and colors.

That's what's great about rock walls, they're very forgiving. Particularly if you plant them. I mentioned plants before, here's a few that occur naturally in rocky road cuts, rock outcroppings, and rocky knolls. Penstemon hterophyllus, Artemisia californica, Diplacus species, Dudleya, and Zauschneria like full sun. Ferns, Fragaria(strawberry), Heuchera, Fringe Cups, and Columbines like moist shade.

Build your wall around the plants. Figure out what kind of wall you want, plan it out on paper and in your head, then plan where in the wall you'll plant the plants. Don't make it into a stress session. This is suppose to be fun!

Leave small gaps in between the rocks in the wall for the plants. Jam the plant in, trying not to rip it up too badly, but it needs to be snug. You can also build the wall with a few well placed gallon sized rocks that are removable so you can insert the plant after the wall is built.

Every day, before you go in after working on the wall, get yourself a wine cooler, beer, iced tea, coffee whatever, and a hose and water in what you've done. Don't make a muddy mess out of it, just set the stones and water the plants.

Plants for a watered wall in sun include California fuchsia, Grape, and monkey flowers.

Plants for a shady wall include Yerba Buena, Heuchera, and Aquilegia.

To see more how to build stuff go to our How to build garden stuff

To see more More rock walls and garden walls.