Using Block Walls Smartly
A block wall design is best used to enhance the natural flow of your landscape’s aesthetics and to stabilize smaller areas of sloping soil. It can also be used in combination with key landscape features to create a beautiful, flowing look where the block design fits in well with the rest of the landscape design.
What Do You Put Under Retaining Wall Blocks?
Of course, all the retaining wall ideas in the world won’t work if they’re not right for the space. Although retaining walls made from CMU blocks may not be the very strongest retaining walls available, they still have to meet local building codes. CMU block walls are limited in potential wall height by the material used. However, they can still work well with the foundation soil (and both lateral pressure and hydrostatic pressure acting on the landscape) when properly designed.
Sometimes, where it’s called for, a CMU block wall may be footed with concrete. However, it’s much more common to use compacted gravel as the footing for block retaining walls.
Gravel is also typically used both to pack around and within hollow wall blocks (unless mortar is being used) and as part of the backfill, ensuring better drainage and the soil support you need.
Why Retaining Walls Need Drainage
When you add a retaining wall to the landscape, you are adding a structure that will change how the water flows over the soil. Often, this is for the better, creating a landscape that drains well and keeps the foundation soil steady and supportive.
However, this requires that the engineering design is proper and correct, and that you use the right materials for the wall height. You should also be aware that wet soil and gardening materials often create an altogether different set of forces, as well as additional weight, on retaining walls.
Retaining walls using CMU block systems are often used where the space is tight or limited, or where access is difficult. These are often the points at which you see water gather, too, so expert drainage design is a must.
Considering Hydrostatic Forces
This factor, called the hydrostatic pressure, is a critical part of the engineering of your wall. Your engineering design must specify a retaining wall that can stand up to all soil pressure and gravity the wall is intended to resist.
This is why drainage is a critical part of retaining wall design. Retaining wall blocks do not always use mortar between them. Sometimes, the pressures acting on the wall are enough to hold the shape, even with the lateral pressure acting on it.
However, it’s far from ideal to have water pouring through your walls. Often, additional drainage will be built into the design of the wall, such as underlying the backfill. This may be necessary to insure optimal water removal, protecting the security and safety of your wall as well as the landscape surrounding it.
The Art of Backfill
Backfill is simply the common term used to describe the material that is returned to the back of the wall. During excavation to create the wall, the foundation soil is usually removed entirely. Prior to replacing the top soil, the excavated soil is often combined with gravel, stone chips, and other drainage-boosting materials, all added as backfill before the top soil is replaced. These drainage materials are lighter and reduce the overall weight acting on the retaining wall blocks, and help to ensure a solid and stable wall construction.
The top layers of the backfill will typically consist of soil for plantings to enhance the landscape. This organic and/or clay-rich soil is normally a very heavy type of soil. As a result of this entire process, the backfill is actually an important part of the overall structure of your retaining wall.
What is the Cheapest Material for a Block Retaining Wall?
There are many different types of material that can be used con build a block retaining wall. Natural stone, sandstone, CMU’s (hollow Concrete Masonry Units) and concrete blocks are all incredibly versatile choices for a block retaining wall, while remaining cheap and practical as well as aesthetically pleasing.
Some retaining walls made with blocks are ‘dry-stacked’, which means that no mortar is used, while other walls will be more cohesively sealed with mortar for additional strength and stability than the blocks alone can provide.
However, when choosing materials for a retaining wall, it’s critically important that the retaining wall ideas you love are also up to the job of holding back the reinforced soil mass (and the weight of any plantings) behind them.
Cost should not be the only factor in the project. The drainage also needs to be impeccable if the ground is to remain stable. So your choice of retaining wall blocks determine more than just the look of the landscape and a preferred style. In the long run a properly designed and built retaining wall is often the less expensive option due to the high cost of repairs that can otherwise become necessary.
Why Retaining Wall Block Designs Aren’t Always Best
In most cases it’s wise to consider either poured concrete or a CMU block retaining wall project for larger projects. Stacked block walls generally become more problematic at heights of 4 feet or more.
Whether a block or concrete retaining wall is best for your specific soil, gravity pressure, and landscape conditions is something your contractor can help you to determine. If all else fails, contact Xpress Engineering and we can provide some guidance as to which wall design may be best for your particular situation.
Professional Engineering Retaining Wall Design – Fast and Affordable
Once you and your contractor have determined what you want and need in a retaining wall, our experienced engineers at Xpress Engineering can perform the “heavy lifting” to design the wall quickly and economically.
We will design the necessary size, depth, reinforcement and specific notes for your contractor to build a safe and beautiful wall.
Are you ready to make a perfect retaining wall part of your home’s landscape today? Feel free to get in touch. We can help to make your retaining wall dream a reality quickly and affordably.