Retaining walls, sometimes called “garden walls”, serve many functions. They can create privacy, screen out wind and noise, define an activity area, retain sloping ground, or accent a garden design.
Low walls can double as a seating platform, and taller walls provide a handsome background for specimen garden plants.
Walls impart a feeling of permanence and quality. Your main consideration in planning a wall are height, material, and structural design.
Deciding The Height Of the Garden Wall
The height of the wall is a critical factor in many respects. Codes and zoning ordinances set limits for wall and fence heights, usually 6 feet for side yards and backyards and 42 inches at the sidewalk line.
You will probably need a building permit if you build above a certain height, typically 3 feet or more. Ordinances often require that masonry retaining walls taller than 3 feet be designed by an engineer, and some areas even require that an engineer design all free-standing walls.
Wall height is also important for aesthetic reasons. Low walls fit the scale of virtually any yard, but a tall wall can have a confining effect if it encloses a small space. On small lots it may be better to build a low masonry wall topped with a wood fence or a trellis and vines.
A wall with openings and grid-work also lessens the feeling of confinement and takes advantage of views.
A tall, solid wall does increase security and blocks noise. To block wind, however, the wall must be right next to the area you want to shelter, or you are better off using a wall or fence with open spacing to subdue the wind by filtering rather than deflection.
There are countless places in the garden where a low wall would be appropriate: surrounding a raised planter, terracing a sloped yard, edging a driveway or walk, bordering a patio, defining a barbeque area, or serving as a fence along a sidewalk or property line.
Several materials work well for garden walls and create interesting effects. The same material can be used for formal or informal walls, rustic or refined, tall or short. Choose a material that matches an architectural feature of the house or garden or that blends with the character of the area.
If you combine materials in the same wall, do not use more than two, and use them sparingly.
If access to the site is difficult, build with small units or irregular or rounded stones for curving walls.
Brick. A traditional favorite, brick is an excellent material for garden walls because it is durable, blends well with outdoor settings, and is easy to handle.
It is ideal for tall walls because each unit is easy to lift, although brick does require a great deal of mortar and joint dressing. It is also expensive and brick construction is time consuming.
Stone. Stone is very attractive and makes an appropriate material for garden walls, especially if you have the good fortune to possess natural stones on your building site.
Building stone walls that last centuries is an art, but with a few simple techniques and great patience you can produce a garden wall that will give you pride and satisfaction for many years.
Wood. Wood is not as permanent as masonry, but it is much easier to handle. A wood wall in an area with proper drainage will last for years if it is pressure-treated or if the lumber is of a durable species.
Used railroad ties are a good choice for retaining walls, although pressure-treated timbers are a more uniform size and can be stained more easily. The simplest wall is of 2-by planking held into place by posts.
Concrete. Although concrete block is easier to work with, a poured concrete wall may be more appropriate where strength or a smooth surface is desired. Short walls are built in the same manner as a simple foundation wall.
They require carefully built forms, but you can recoup form-building time when you pour because the wall and footing can be poured together. Any wall over 3 feet tall requires special forming and steel reinforcement.
Consider having a contractor build any major concrete retaining wall, then covering it yourself with a stone or brick veneer.
Concrete Block. Concrete block is inexpensive, easy to work with, and produces a strong wall quickly. The favorite block for garden walls is slump block, which has irregular faces that provide interesting relief.
Other decorative types are also available, or build a wall of structural block and cover it with a veneer of brick, facing stones, stucco, or another more attractive material.
Adobe. A variation on bricks and blocks, adobe is a common wall material in the Southwest. It is not a durable as other materials and is losing favor to slump blocks. Adobe is either covered with stucco for weather protection, or stabilized with asphalt emulsion, then sealed with a clear sealer. Most blocks are 4 inches thick, 16 inches long, and from 4 to 12 inches wide.