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Maybe you’ve heard about retaining walls, maybe not. Whichever the case, one of these could be more of a necessity than you think, depending on your yard’s layout and soil composition. Here, we will cover a retaining wall’s purpose, the cliff notes on planning one, and the cheapest blocks you can use. Check out our guide to the cheapest retaining wall blocks below!
Cheapest Retaining Wall Blocks: Purpose of a Retaining Wall
Perhaps you have been on roads that feature a wall right next to a hill; it is also possible you have seen such walls as the outer limit of a dirt mound. Such is the purpose of a retaining wall: holding back soil, keeping it contained. Lawns located in areas that are moist or prone to flooding would greatly benefit from a retaining wall, to prevent the soil from getting washed away.
While there are times when a retaining wall is a matter of safety, it can also be a great way to reclaim space you are otherwise unable to use. If, for example, you have a steep decline in your yard, you can build a retaining wall on the side, level off the ground on top, and turn that formerly vacant space into a terrace or a patio. Another common application is on flowerbeds: instead of placing them at ground level, you can create a soil block at a higher altitude and confine it with a retaining wall, which will make your flowers easier to see—and to tend to!
Before You Begin
As with many projects around the home, a retaining wall will benefit from involving a professional, but it can also be turned into a DIY project with the right tools, sufficient know-how, and certain sensible limitations. Here’s what you need to keep in mind.
1. Ask for Permission
Erecting a retaining wall may have some repercussions, such as affecting the natural flow of water. For this reason, it is always better to check with the relevant authorities before doing any building. Don’t forget to verify if there is a height restriction—sometimes that’s a thing. Another party you might want to notify: your HOA. Rules currently in effect might regulate retaining walls… or restrict their implementation altogether.
One more thing: we will cover this more in detail further down, but the process of your retaining wall will involve digging. This means that, for your own safety and that of your neighbors, you should give DigSafe a call (just dial 811), so they can tell you if there are any utilities beneath the area where you will be working. This step should not be skipped, as utilities might not be buried as deep as you think, and slamming a shovel in the wrong place could bring about unpleasant consequences.
2. Choose Your Height
A word of warning: the taller the retaining wall, the more complex its construction will be, as it will be holding back a higher volume of soil and this increases the pressure it is subjected to. DIYers are usually advised to make their walls no higher than 4′, and bring in a professional for anything higher.
Should you absolutely require a taller wall, a simpler solution is creating two walls, one in front of the other; this way, each wall is holding back a lower volume of soil, and you get the height you need. Position is key—the wall at higher tier should be placed at a distance equal to double the height of the wall that will be at ground level. If, for example, you go for a full 4′ height on your lowest wall, then your next tier should be laid down 8′ behind. This is necessary in order to prevent the higher wall from adding pressure on the lower one.
3. Set Your Layout
Now that we’ve settled on height, the first step is marking the line. For a free shape, you can use a rope or hose to indicate the path; straight lines can be traced by driving stakes into the ground and tying some sort of string between one and the other to get a visual reference. Mason line is a good option for this job. When you have to make a curve, tie a length of string to a stake, then drive the stake into the ground so that the string’s end will be right at the edge of your line. Using the string as a sort of compass, trace the curve using marking paint.
When the line that your wall will follow is fully traced, the next step is to measure its length, and divide it by the length of your chosen block.
4. Foundation Is Key
Remember when we mentioned you would have to dig as part of the process? This is because, even if you were to make your wall out of a solid block of concrete, the pressure of the ground being held back could force it out of position if the support beneath it is not appropriate. To prevent this, the base of your wall must be a trench, with a layer of crushed rock at the bottom.
Your trench should be deep enough to hold an eighth of your wall’s total height (the visible part plus the buried section), with an additional 3 inches; this little bonus is the thickness of your crushed rock layer. To determine how much you ought to dig, divide the (visible) height in inches you want for your wall by 7, and add 3 inches.
For example, let’s say we want our wall to stand 4 feet from the ground; that’s 48 inches. Dividing by 7, we get about 7 inches, plus 3 for the crushed rock bed—that’s 10 inches you should dig. In this example, the total height of your wall will be 55 inches. Divide this by the height of the block you chose, and you get the quantity required to raise your wall all the way.
5. Crunching the Numbers
Time to find out how many blocks are needed for the entire wall. To do this, we multiply the blocks required by length by the amount required by height. This will give you a fairly good estimate on how many you will need, although it is often recommended to buy an extra 10%… just to be safe. Then there’s also the bed for the foundation we discussed before, backfilling and pipe for drainage (lest the soil accumulates water and ends up busting your wall sooner or later) and, of course, other odds and ends:
- Safety gear. This should include a back brace (as you will likely be hoisting heavy loads), safety glasses and safety gloves.
- A shovel, for the digging that will need doing.
- Your wall will benefit from a layer between the blocks and the backfilling that will help with drainage. Landscape fabric is the usual go-to for this purpose.
- Another thing that is important when laying down the wall is, it should be perfectly even; any deviations from the horizontal will compromise the entire thing, preventing the blocks from achieving a cohesive formation. A carpenter level will help you ensure your line is perfectly even as you lay it down.
- Your block of choice might require cutting or correcting. This will call for a drilling hammer, a masonry chisel, and a circular saw with an appropriate blade.
Selecting the Most Budget-Friendly Material for the Cheapest Retaining Wall Blocks
Three are the most common, nearly universal, choices when it comes to building a retaining wall. One is stone, which is generally the most expensive and should therefore be stricken right at the start. That leaves us with two, which we will cover forthwith.
This is easily the cheapest material, but only at the onset, as wood is more vulnerable to rot and is likely to require repairs far sooner than our next option will; another common issue is that any design you come up with will have to be rather angular, without any curves. This may explain its decline in popularity for retaining walls, although it remains an optimal option when money is a prime concern, or for those who are looking for a more rustic look.
It’s perfectly possible to select poured concrete for your wall, and it is also fairly low in cost if we consider only the material; however, average DIY enthusiasts cannot handle this one, and even if they could, the cost of the equipment required will quickly turn this into a rather expensive project. Repairing it when necessary will not be particularly easy or affordable, either.
The other way to use concrete is in the form of blocks. This option is not prohibitively expensive, it’s quite strong, and it is also easy to lay down—all it takes is placing the blocks one on top of the other.
Cheapest Retaining Wall Blocks: The Better Choice
It is our belief that, for most retaining walls, concrete block is the optimal way to go, as it combines strength with portability—unlike timber or actual concrete, blocks are a breeze to transport. Given how easy it is to create a wall with these blocks, this is also the best pick for those who are undertaking such a project for the first time.
This alternative is so popular, there is even a rather specialized variety called interlocking blocks. As the name implies, this type of block is designed to lock onto its neighbors, making for a steadier wall. The size of the blocks also makes it easier to form smooth curves, making it great for uses such as creating a circular flowerbed in the midst of your yard.
Having said all this, it is also true that DIYers should pick the material they feel more comfortable with, as it will make the entire project easier to tackle. In the end, particular needs and personal preference are relevant in their own right.