There was already a wooden retaining wall descending into the garden, but I knew that if I was laying stone over the backyard, the wooden retaining wall would decompose LONG before the stone did, and I’d have an expensive nightmare on my hands. It made sense to remove the wooden retaining wall and replace it with a stone wall that would integrate seamlessly into the backyard.
My friend J-P suggested that I raise the retaining wall above the level of the backyard, turning it into a bench along the garden which would also prevent people from falling off the 2′ drop into the garden at night during parties. Brilliant! The less I have to worry about lawsuits, the better.
The first task was to rip out the landscape timbers. Using heavy pry bars and a chainsaw, an afternoon of grumbling and grunting and the timbers were all out. We discovered all sorts of cool snakes and insects and lizards living behind the wall.
My friend Karen, who works for an attorney who sues contractors, said we needed to get the new wall in place immediately. If it rained too much and the ground slumped where the retaining wall used to be, the slab foundation of the house could crack! Ugh…
I posted the used timbers on the FREE section of Craigslist, and within an hour there was a guy here taking them for use in a haunted house. They were dirty and had rusty rebar sticking out of them, and I had mentioned this in the ad, but that didn’t stop more than 30 people from emailing in the first hour! Craziness!
The next step was to pour footings for the cinder block wall to sit on. The footings were constructed of 2x4s, and we ran 3/8″ rebar inside the footings to make them stronger and resistant to cracking. The footings need to be level front-to-back and side-to-side. (I dug the footings into the ground rather than setting them on top because the soil would be more compact. This is my garden and I till and aerate the soil every year, so it’s not compact.) Then, you pound wooden stakes into the ground, and then you level the 2×4 against the stake and screw the stake to the 2×4 to secure it. Then you lay the rebar into the forms and tie it together with wire.
Building forms for footings for the retaining wall
In colder climates, you need a much thicker and deeper footing. But because we rarely get hard freezes that last longer than a day here in Dallas, we don’t need “frost” footings like you folks do up north. If you live in a freezing area, you need the footing to reach below the frost line, which may be several feet deep in cold areas. That’s a LOT of concrete.
Lucky for us, we only need 4″ footings, so I started mixing concrete.
Yes, that’s a concrete mixer. You can rent them for about $40 a day, but because I’m pouring HUNDREDS of bags of concrete over the course of this project, I bought one used on Craigslist. It was in practically-new condition, and this model costs $650 new. (Though you can buy cheaper models for $200-$300.) I paid $200 for this used model, and I plan on selling it for $300 once I get done.
Concrete comes in 60- and 80-pound bags, which cost around $3.50 – $4.50 each. Sometimes you can get them on sale for cheaper. I don’t remember exactly how many bags it took to pour the footings, but it was between 20 and 25 bags. I ran about 40′ of footing 12″ wide and 4″ deep. There are Concrete Calculators online that will tell you how much concrete you need so you can plan ahead. Always buy a few extra bags…you can always return them.
Just shovel the concrete into the forms, move the shovel around to make sure the concrete fills the form completely and runs all around the rebar. Overfill the form a little bit, then run a 2×4 across the top of the form, zig zagging it back and forth. This is called “screeding” and it gives the concrete a nice level surface. Since I’m leaving the wooden form in place, and since I’m just laying cinder blocks directly on top of it, I don’t have to do any more finishing.
Now you just cover the concrete with a layer of plastic and let it cure for at least a week. It’s April here, so the days are getting really hot. You want concrete to cure slowly to reach its strength potential, which means you want to slow down the evaporation of water inside the concrete. This is what the plastic is for. It’s also a brilliant idea to mist down the concrete with water a couple of times a day for several days.
Now that the slab has cured, it’s time to lay cinder blocks! Also called concrete blocks, these things are pretty cheap (about $1.50 each at Home Depot), but I need HUNDREDS of them for the whole renovation, so I kept an eye out on Craigslist.
My first haul was a load of 50 FREE cinder blocks. To get ANYTHING from the FREE section of Craigslist, you have to be the first person to contact the poster…which means you have to be lucky enough to see it immediately after it posts. I saw the ad 2 minutes after it was posted. There was no contact information, just an address in Grapevine, about 10 minutes away, and an invitation to “come and get em!”
I frantically drove to Grapevine and loaded by RAV4 to the gills…there were even cinder blocks on the dash board and in my lap as I was driving! But I got them for free. I had to purchase about 15 extra blocks from Home Depot to finish the wall.
Laying cinder blocks is easy…you mix up mortar ($4 a bag which will lay about 20 blocks), you use a pointed trowel to toss mortar onto the foundation, and you set the block into the mortar, tapping it gently to seat it firmly in the mortar. See if it’s level both ways using a level. If not, pull it back up and put a little mortar under the low side. Once you’ve got one row of level blocks, the others lay down level and you don’t have to be so careful.
The wall rises 6″ above the ground level, so it will also serve as the retaining curb for the 6″ of gravel which will sit beneath the flagstone. Along the long side of the garden, it sits 26″ above the ground…6″ for gravel and 20″ to serve as a bench. Later I’ll pour a nice stained and imprinted concrete slab to lay on top of it to serve as the seat.
The finished retaining wall, which will eventually be faced with flagstone
Those railroad ties you see behind the retaining wall are for the pergola, and they are reclaimed from a defunct railroad in Arizona. They cost me $8 each from a Craigslist guy who has a small business buying and selling them. New ones are $20-$50 each at landscape supply yards and are so soaked in creosote and tar (preservatives and insecticides) that they’ll ooze for years all over your lovely flagstone. These are decades old, and though they are still well preserved and do have creosote at their hearts, they are solid and dry on the outside and won’t leak. But that’s a future project…