Retaining Wall Base

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Tea Rochlitz

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Aug 4, 2024, 6:36:34 PM8/4/24

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Usingcrestone blocks 3.5 inches tall by 11.5 w and 7.5 deep. I will be doing two levels plus caps. What base depth should base material be? I know base brick should sit 1 inch deep for every 8 inches of wall, but how deep should base be?

The depth of your 'foundation' should be 4" compacted crushed gravel plus one row of your CMU (concrete modular units). Behind that wall and sitting below the gravel is a perforated 4" pipe wrapped in landscape fabric and back filled with drain rock. Daylight down slope and there should be a down slope so you control the surface water. Do not drain onto your neighbor's property. I've always had to install a simple drywell; a pit with landscape fabric, drainrock (rounded cobble) another layer of landscape fabric then covered with a thin layer of drainrock. The size of the pit is determined by the surcharge behind you wall and the length of your wall and your area or zone.

Make sure each of your walls are no more than 3' or you shall be eligible for permit fines if they find out. One wall no more than 4'. Check your codes. Behind the two walls make sure you slope the soil away from the wall about a foot or so down into a little 'swale' to collect surface water and drain towards that drywell pit as well...so bigger pit: Say 4'X6'X3'? Or more?

Do you have enough depth to your property you could make at least 4 maybe 6' bed between the walls with a mini swale such as the one I described behind the top wall? If you want to plant that first wall you should put as much space as you are able. Install perf drain pipe behind both walls. How much surcharge is behind those walls or slope? Send a picture. Drainage will make or break your all your work. I am not kidding. I am glad you are doing a cap. I don't know if you've already selected your cmu but I would suggest as a profession to use ONLY grey with a light grey or concrete cap. The wall should be 30 % dark grey to make it look more natural. That cap should be a very light concrete color. Any color will LOOK DIY. Reds, browns will look like your wall is dirty or has a very nasty infection. Just some tried and true tips from a licensed landscape architect and construction install project manager...blah blah blah. Dove grey is the only color I ever use for architectural structures in the landscape. Comes from my background in Japanese garden design principles. Gravel, concrete, decks, pergolas, arbors and garden walls are always dove grey to allow your plants to be the focus, not say, the fire engine red fence? Grins.

It has always been a no no to use your home's foundation drain as well as storm sewers to direct excess water. Perhaps your codes are different but the reason for that is you do not want to encourage MORE water to travel to any foundation or concrete. Water is pretty destructive. I've had a hard time with the rules for not being able to use the storm drains. That is why I love dry wells. Check your codes but it isn't a good idea to ever encourage water to drain towards your home's foundation even if it is into a pipe.

Then I need to know the distance between your wall (the radius is it based on your CMU's for a curvature)? Is there a scale I could use or did I miss that? I am disturbed there is a slope between you and your home. That means water is not only draining through the soil towards your wall but towards your home's foundation. Do you know there is a decent foundation perimeter drain? Do you have a basement? Do you know if your foundation has asphalt emulsion between soil and concrete? Is there a drain in your basement if so where does that go? And this sump pump. Now that really worries me. Tell me more about this pump; where is it, what is its purpose, how often do you have to use it? Sump pump just tells me a band aid is in place to cover up a problem that you might be exacerbating? Also, that perf pipe should be on the same level as the bottom of your gravel foundation, not an inch or two above. It might not be a big deal if I knew more but if you've not installed this pipe try to do so. Back fill is NOT soil, it should be drainrock. You want to encourage water to go towards the pipe that allows excess water to flow en mass to a proper spot. What will the elevation of the patio at the foot of your wall be? Why 2 walls that close to your home. Shoot. I need more information. How about a picture of the area, excavation in relation to your home's foundation? Get back to me, okay? This could be a beautiful addition to your home and if done correctly will add big value to your home. What planting do you imagine above that wall. Is it really going to take two walls to accommodate that slope? Pictures. I'd rather do this on site but am learning to try being 'virtual'...

Proper installation of landscape retaining walls can make sloping lots usable while managing both soil and water runoff. In addition to serving a functional purpose, retaining walls also add aesthetic appeal to your landscaping. Use them in home gardens to highlight flower beds, patios, or yard features.

While retaining walls are made out of many types of building materials, a block system is a popular choice due to the easy installation features. The blocks are made from cement and lightweight aggregate materials.

The size of your wall depends on the size and shape of the space you have. Map out and measure your layout using stakes and string pulled tightly. When installing a curved retaining wall, use a garden hose and spray paint to mark and map out the curved radius.

Preparing the base where the first layer of block will be placed is critical to building a well-placed, stable retaining wall. Dig a trench for the bottom row of blocks. They should be buried about 1 inch deep for every 8 inches of wall height. This provides strength and stability to your retaining wall. Make sure that your trench is level and compacted.

The base material should only consist of angular, sharp-edged particles such as -inch minus gravel. The various-sized crushed gravel with the fines helps ensure the right amount of compaction. Round rocks, such as pea gravel, roll and dislodge under pressure resulting in failure of the retaining wall.

Using the appropriate type of compactor for your site size (either powered or hand-operated), level and compact your base material. This is very important! The base should be so compact that, when you walk over it, it doesn't shift at all.

When building a straight wall, establish a string line along the back side of where the first layer of blocks will be placed. This will provide a guide to help ensure the wall is straight. Obviously, this will not work when building a curved wall.

Use a rubber mallet to tap each block in place. Check the level of each block using a small level, front to back and side to side. If not level, adjust the block by lifting it and placing a small quantity of bedding material under the appropriate low side. Reset the block with the rubber mallet.

Use a masonry chisel or diamond saw to split a block in half. Where needed, use half blocks to create the correct spacing for the next full block, ensuring that it straddles the joint in the row it is resting on.

Compact the backfill before starting on the next row of blocks. You should clean and sweep the top of each row before placing the next one. Even a small amount of loose material can keep the next blocks from sitting firmly in place.

There are several options for capping material. For some types of retaining wall block systems, there are corresponding capping stones that are designed to match the design of the wall block. In addition to products made of concrete, there are also various types of flat stones or flagstone.

Typically the capping material is glued into place using an adhesive similar to construction adhesive but made specifically for masonry products. Generally, the wall material needs to be dry to ensure good adhesion.

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When it was time to add the top caps, I stagger them backwards and forwards to get them to go straight across without spaces between. The adhesive I apply will prevent the top caps from moving if kiddos walk on the wall. When the wall is built, backfill your trench and ensure the ground covers half the height of the first row of blocks.

All in all, it took me 6 hours to build a small retaining wall. It is a great way to add function and landscaping to my yard. I have never done this before and I thought it was going to be hard. But it was doable by myself in one afternoon for only about $150!

I love coffee and creating, snuggles with my kiddos and volleyball with my husband. My 130 year old farmhouse has a modern aesthetic and I strive for a minimalist lifestyle. Join me for my adventures in crafting, decorating, renovating, + more!

Anyone with a strong back can stack up a bunch of blocks and build a pretty stone retaining wall. But it takes skill and planning to construct an attractive wall that can also handle immense pressure, shrug off the forces of gravity, stand for decades and laugh in the face of Mother Nature.

Use a torpedo level to level each block front to back and either a 4-foot or 6-foot level to keep each course level and even. Set the blocks with a heavy rubber or plastic mallet. Getting the first course flat and level is extremely important, so take your time. Try to lay the course as close to the center of the trench as possible.

Even a small pebble on the surface of a block will throw the one above it out of alignment. And that crooked block will affect the one above it, and so on. That little stone could eventually create an unattractive hump in the top course.