Modern concrete block walls are fairly sophisticated systems designed for strength as well as for fast, easy assembly. You simply stack the blocks on top of one another and secure them with pins, clips or interlocking edges. They're designed to be set on a compacted gravel base. This allows them to flex slightly with ground movement and still remain strong. They're available in a wide variety of styles in two basic sizes.
The garden wall size is the most common. These are relatively small (about 12 in. long x 4 in. high) and work best for accent walls around the yard and garden up to about 30 in. high. They're perfect for terracing or building a raised planter. They're lightweight (less than 25 lbs.), quick to install and widely available at home centers, nurseries and landscape supply outlets. You can usually build a wall with this size block in a weekend.
For heavy-duty walls up to 30 ft. tall, go with full-size blocks. They're 16 to 18 in. long x 6 to 8 in. high and weigh 50 to 75 lbs. You'll typically find them at landscape supply yards. Working with these blocks is a big job best left to pros. Big walls usually entail excavating and moving tons of soil and gravel as well as the heavy block itself. Walls over 4 ft. tall must be designed by a licensed engineer to ensure adequate strength.
If you think concrete block walls look cold and commercial, look again. You now have a wide variety of shapes, textures and colors to choose from. Select one that blends well with your yard, gardens and the exterior of your home. If possible, look at a completed wall to get the best idea of the appearance. Almost every manufacturer produces these four main styles.
Stacking systems for concrete block
Almost every style of block is made in two weights and in one of several stacking systems, depending on the manufacturer. The stacking system evenly spaces the blocks, holds them in place and allows the flexibility required for corners, curves, steps and other design features. Pick the weight and stacking system that best handles the design details of your wall.
Design issues with concrete block
Begin your planning by making a sketch of your proposed wall, including curves, corners, stairs, junctions with the house and any other details. Add dimensions to the drawing so you (or the staff at the landscape yard) can estimate the number of blocks you need and which special blocks to order. These details will also help you decide which block system to choose. Don't skip this step; it'll save you hours during construction and prevent big headaches. Be sure to note curves, corners, steps, caps and setbacks.
Natural stone walls
Stone makes the nicest-looking walls of all. You have a wide variety of choices that will fit just about any style of yard and garden. On the downside, stone is usually more expensive, and the walls require more skill and more time to build. They'll give your creative skills a workout, as well as your shoulder muscles! Limit your efforts to walls up to 3 ft. high. Pros can build higher stone walls, but typically they require engineering expertise. Stone walls fall into three main types: rubble wall, cut stone and boulder walls.
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Wood plank or timber walls
Although fading in popularity, wood walls complement some yards and homes, especially if the home has a rustic appearance (such as stained wood and stone). It's also a good choice when cost is an issue. You can use either standard lumber (2x4s, 2x6s, 2x8s, etc.), or timbers (4x6s, 6x6s). You can easily incorporate multiple angles and steps. And they're a great project if you're a carpenter at heart. The timber style, which is the most common, gets most of its strength from 6x6s set perpendicular to the face of the wall. A crossed 6x6 at the rear adds additional support. As with other types of walls, set the timbers on a gravel base and provide good drainage behind the wall. Fasten the timbers with long spikes or screws. Choose timbers that have a .40 treatment rating (suitable for ground contact) and seal any cut ends with preservative to prevent rotting. Timbers are usually available in green and brown.