Today we're going to take you step-by-step so that you can build your own retaining wall. Covering some of the most vital parts in retaining wall construction. Including the excavation and the initial sub-grade protection which will be the main component to the longevity of your wall being straight and perfectly flat-topped, or ending up years down the road having a wave in it. We're going to help you eliminate that. We will also be looking at the material used in your first course of block. How to base and level that most critical element: the very first block that goes in the ground Then we are going to show you how to construct a 90-degree corner in case you happen to have any of those on your site. Take your project from something that looks like this, to something that looks like this.
The very first step we've got to do is remove the existing CMU (Concrete Masonry Unit) retaining wall and prep the sub-grade. Most of the old style concrete masonry unit retaining walls will have a really thick deep footing; the wall itself will fall out like a knife going through hot butter but when it comes to that footing that's buried below grade, that was how those retaining walls lasted. So you're going to end up using some heavier equipment. You can use a jackhammer or even a mini excavator to get that footing out but when you're going into the situation. Don't get yourself in trouble thinking that the footing is going to come out as easy as the rest of the retaining wall. Once you get that footing removed, you're going to be very careful with the sub-grade. You've got to make sure that it reaches full compaction. I prefer to use either 150, 400 or even a 1000 lb. plate compactor just to make sure that the sub-grade soils are adequately compacted before my base material goes in. Which will be 6 inches of 3/4 inch angular stone such as a granite or limestone. I never use pea-rock, and as a back-up if my angular stone is not available, I will then use class 5. But, it is not my first choice. I like the angular free draining because it allows water to pass underneath the retaining wall and away from the structure.
Laying that first course of block is the most critical element to the overall longevity of this retaining wall. It must be leveled individually front to back and side to side, but then you have to take it one step further and get that single block in level with the block next to it. The level must slide smoothly across with absolutely no ridges, no hesitation between the two. The batter from the front of the block to the back of the block must be either completely equal or with just a slight bubble. Don't go too aggressive with your pitch back into the hill, otherwise what will happen is the bottom of the retaining wall will have too much pressure, the top will lean back too far and the bottom will blow out. These plots are designed to be installed with a level bubble but some people prefer to put just a touch of a bubble and give it just a slight shift backward. Be cautious if you're not familiar with these techniques and stick with what's safe, go with the level bubble.
The next critical element to the overall success of the retaining wall is the draining zone behind it. The recommended minimum depth is 12 inches. What you’ll find on retaining walls, we extend that out 18-24 inches. Allowing the water to go behind the wall and then percolate through is a critical element to keeping hydrostatic pressure from building up and blowing out a retaining wall. It's a very simple step. It's cheap insurance but it has a big impact on the overall quality of your project. So make sure you put enough drainage aggregate in. The drainage aggregate is the exact same material as we used for the base aggregate. A three-quarter inch free draining angular stone that locks in place.
The first thing you do is score with a chisel. Then you simply take a chisel and a mallet and you keep tapping all the way 360 degrees around that block. Eventually, it will snap. When it snaps it will leave you the same texture on the face as you have on the side. Don't take the chopsaw out. If you attempt to cut it all the way through, you'll end up with a smooth face on the side and a rough face on the main part. It won't match. Both faces will be exposed on that 90-degree corner, so it’s critical that both faces have the same rough texture. The hammer and chisel method is quick, it's easy, and it leaves you with both faces matching. The three most critical elements of the success of your retaining wall are compacting the sub-base (that's this raw soil), then placing your base material giving that a light compaction. Get that first block put in place and level it individually. But then take the time to level it with the rest of the blocks in that row. That will give you that nice flat top that will last for years. Then make sure that your drainage zone is a minimum of 12 inches, and don't be afraid to extend that out even further. 18 inches 24 inches is only going to benefit the longevity of that retaining wall. When you get those three components put into the right order, you're going to have walls that never go anywhere.
God bless, love you guys! I hope this has helped you out. My preferred retaining wall material is Versa-Lok units. I want to hear from you what kind of blocks do you use. In what area of the world are you? what is your preferred material for building retaining walls?
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