Hilly terrain creates the need for retaining walls, making them mandatory in many places. Walls can be used to terrace slopes or to enlarge usable areas for outdoor recreation, patios, walks and driveways. Retaining walls are also used to define landscaped beds and rock gardens.
Walls are commonly constructed with natural stone, timbers, or precast blocks. While railroad ties were often used in the 20th century, their creosote content prevents present day use. Natural stone creates a beautiful wall, but building a wall with irregular stone can rapidly discourage an amateur stone mason.
Precast wall stone has become widely available in recent years, providing homeowners and professionals with a uniform-sized product that is easier to build walls with than irregularly shaped stone. Precast products provide multiple color choices to match existing home construction and suit individual tastes.
Really need it? Don't build a wall unless you really need it. There's considerable expense with initial wall construction and most walls will eventually need to be rebuilt due to wall movement.
Got the muscle? Wall stones and timbers are typically very heavy, so be sure you have the physical strength to handle a wall project. Wall construction is hard, heavy work, even for strong individuals in good physical condition.
How steep is your slope? Proper wall design becomes much more critical as slopes get steeper, and as drainage and clay soil conditions worsen. Basically, the taller the wall, the more critical it is for proper construction. Extremely high walls should be designed by an engineer.
How's your access? Wall construction often requires the removal of large amounts of soil and fill, so be sure to allow for removal and disposal of this material. Soil volume increases as it is excavated, so where will it be placed? It's not unusual to hit rock while excavating for a wall, so heavy equipment and a jackhammer may be required. Do you have good access for a backhoe to reach the work area? How much damage will heavy equipment excavation work cause and what will be involved with repairing damaged lawn areas?
Got storage space? Walls need good drainage behind them. This requires the delivery, movement and placement of several tons of 2b crushed limestone, or a similar product to promote good drainage, behind the wall. Do you have someplace to store the gravel and a way to move that stone into the work area? This storage space will be needed in addition to your storage area for wall product, so plan ahead, especially if it will block access to your driveway and garage.
Using quality products? More people than you know have made the big mistake of buying inferior wall products, primarily wood timbers that weren't properly pressure treated for soil contact. Some wooden "landscape timbers" will start to rot in 3 to 5 years, requiring their removal and replacement shortly afterwards. Check product warranties and try to buy quality products that will last.
White haze? Unfortunately, some precast stone products begin to show efflorescence after a few years. Efflorescence is the growth of salt crystals which appear as a white powder on the surface of some precast walls and other masonry work. While it can be easily removed with power washing, it will usually reappear within a year or two.
A good foundation. The foundation and first course of your wall is the most critical for easing ongoing construction of the wall and adding to its longevity. Most wall manufacturer's specifications call for excavating at least 12-inches of soil below the ground surface, and tamping-in a layer of crushed stone for good drainage on a firm base.
First and foremost! Again, how well you lay that first course of wall stones or timbers determines how well the rest of the wall will turn out, so take your time and get it right. The base course is no time to rush! Add a French drain pipe at the rear of the base course (surrounded by gravel) to promote water drainage from behind the wall. Add more gravel behind the wall as additional courses are built, since good drainage is a major key to wall longevity.
Pancake batter? ...NO, “wall batter." For every 4 feet of vertical wall height, it's usually recommended that your wall "lean back" 1 foot horizontally (3-inches per 12-inches of height). This keeps some of the wall's weight leaning against the retained soil and helps to hold back the ground. Many of the new precast wall products have “wall batter” built into the product, “stepping the wall back” as it’s being built.
Deadmen tell no tales... In timber wall construction terminology a "deadman" is a timber tie-back into the slope to help maintain the wall's structural integrity. Deadmen should extend several feet into the slope, and the more deadmen you use, the stronger the wall becomes, so don't scrimp. Below we see a photo what happened within a few short years to a timber wall constructed without any deadmen:
Watch your back! Whether you're lifting wall stones, timbers, or shoveling crushed stone, practice proper lifting techniques. If you aren't physically able, consider hiring a professional.
Need a fence at the top? High walls should have a fence or other barrier along the top of the wall to prevent injuries from someone stepping-off or falling over the edge. Check building codes.