Repair & Improve

Building a Retaining Wall

What you’ll need for a structure with staying power

by Tom Kraeutler, AOL Home Improvement Editor

Tom Kraeutler is the Home Improvement Editor for AOL.  In this column, Tom offers tips on building and maintaining a retaining wall.

A well-built retaining wall has many benefits: structures are protected from soil eroding either away from or toward their foundations, the integrity and features of the landscape are preserved, and new outdoor rooms for leisure and recreation are created. The style, materials and construction you choose will depend on the terrain you’re dealing with, but the basic ingredients and considerations stand solid across most types of retaining walls.  Here’s where to begin:

SCALE - The higher and broader the retaining wall, the more complex the construction and planning will be, so consider hiring a pro to help with anything over three feet set in a complicated soil situation. The wall’s cap-to-foundation dimensions will also depend on the climate you live in. Frost is one element that has a real knack for making retaining walls buckle and pop, so if your wall will experience harsh winters, you’ll need to excavate and anchor it well past the typical point of underground freezing.

CODES - If you’re scaling a wall project on your own, do some research before you start digging. Local building codes may require permits and other documentation for any structure over a yard tall, and some pretty important utility lines could be running right through your project area. So be sure to get your plans approved and the utilities literally staked out.

MATERIALS - Several options are available to you and your property, depending on the considerations above.

• Pressure-treated timber: Though not as long-lasting as masonry options, this material provides a rustic, natural look, and can usually be implemented for do-it-yourself walls up to four feet tall. Timber selected must be marked “For ground contact” to prevent soil and water contamination.
• Interlocking concrete blocks: This mortarless solution comes in various sizes and styles, with integrated connectors and a slightly tapered design that enables the creation of curves in the wall’s footprint. Most systems also incorporate flat units to cap the surface. Maximum height for block construction varies, depending on manufacturer specifications and soil conditions.
• Stone, brick or cinder block: These definitely fall within the province of the pros for guaranteed results in masonry craftsmanship and construction quality. Cinder block requires the addition of textured facing to match up to the natural good looks of stone and the traditional charm of brick.
• Concrete: An experienced pro is also your best bet when it comes to concrete construction─it’s a complex job, and one wrong move can lead to a cracked wall that has to be completely replaced. If concrete is in the plan, discuss decorative options for the finish. Many dimensional patterns can be impressed directly into the surface, and veneers such as those from Owens Corning’s Cultured Stone line can be applied for a custom, natural look.

REINFORCEMENT - Any wall you build should lean into the earth it’s retaining at the rate of one inch for every foot of height. It should be further stabilized by ties and anchors that reach deeply into the earth behind the wall, the style and size of which will vary according to wall materials used. A timber wall over four feet high, for example, calls for 6-foot-long, T-shaped anchors; other systems have anchors integrated into their construction.

DRAINAGE - Proper drainage around the retaining wall keeps soil and sediment from clogging up the works and allows water to escape in such a way that the wall’s integrity remains intact. Start by lining the cavity behind the wall with landscape fabric, and replace part of the native soil you’ve removed with gravel. Then lay in a system of perforated PVC pipe, and cover with well-tamped gravel and topsoil.

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