All About Retaining Walls
You, our TOH online community members, told us that building a retaining wall tops the summer to-do list. So we lined up the experts to help you create a sturdy and stylish structure for leveling your landscape
Nature's uneven terrain has its charm, until you try to play croquet on a hilly lawn or enjoy a candlelit dinner on an off-kilter patio. Install a retaining wall as a backstop, though, and you can literally carve out functional outdoor spaces where once there were only precarious slopes.
More than problem-solvers, retaining walls also have a sculptural quality that adds definition to the landscape, and they can be made from various materials to evoke different styles. Stacked timbers or mortared stone, for instance, can impart a rustic look, while poured concrete is sleekly modern.
Just keep in mind that when planning for a wall meant to hold back tons of soil, there's little room for error. How effective your wall will be and how long it'll last—decades or just a few years—depends largely on things you can't see, such as a sound footing buried in the ground and drainage to keep water from building up behind the wall.
Shown: the curves of this mortared-stone retaining wall add architectural appeal to a structure designed to keep soil in place. Steps built of the same material blend right in.
New England Fieldstone, Boston Blend, about $11.60 per square foot uninstalled; The Stoneyard
The basic parts of a mortared-stone wall. Components can vary for other wall types.
Keeps water from collecting behind the wall
Prevents soil from clogging drainage stone
The backward lean into the earth, about 1 inch for every 1 foot of wall height
Spaced every 6 to 8 feet, it lets water drain through the wall base
Reinforced concrete supports the wall
Carries away water
How much do they cost?
Prices start at $4.30 per square foot for poured concrete, $5.65 for interlocking concrete block, $6.15 for pressure-treated pine, and about $11 for stone. Installation or supplies, such as drainage stone or filter fabric, are not included.
How long will they last?
Timber can last up to 40 years; there's no limit on the life span of a properly installed masonry or concrete wall.
DIY or hire a pro?
Timber and inter-locking-concrete-block walls are DIY-friendly. Mortared masonry and poured concrete ones are usually best left to a mason.
Does height matter?
Codes mandate that walls taller than 4 feet be designed by an engineer and built by a professional.
How much care?
Other than an occasional clearing of the weep holes, retaining walls don't need much attention.
Affordable and good for DIYers; the 6x6s, 6x8s, and 8x8s sold in lumberyards and home centers are held together with screws, spikes, or rebar. These walls need only a basic crushed stone footing and T-shaped timber deadmen to anchor them. Pressure-treated pine and fir that are rated for ground contact should survive 40 years; western red cedar or redwood lasts about 20.
Cost: Pressure-treated pine, $6.15 per square foot uninstalled; Lowe's
With sufficient drainage, stone, brick, or concrete-block walls are strong and long lasting. You can buy these materials at stone yards and home centers, but you'll likely need a mason to install them. Mortared walls rest on a rebar-reinforced concrete footing set below the frost line and require weep holes to relieve soil pressure. Mortar-free dry-stacked stone walls need only a crushed-stone footing.
Cost: Fieldstone, $11 per square foot uninstalled; The Stoneyard
The strongest and most durable choice, it can be stamped, stained, veneered, or carved to look like mortared stone. Buy concrete dry, in bags from the home center, or wet, delivered by a ready-mix operator's truck. Leave the design, formwork, and pouring to professionals. Like mortared masonry, these walls are supported by a reinforced concrete footing and require weep holes. This is the only wall type that isn't battered (leaned back) against the earth.
Cost: Ready-mix from a truck, $4.30 per square foot uninstalled; C & C Ready-Mix Corporation
An easy choice for DIYers because of their light weight, flat sides, and the foolproof way they fit together without mortar. These blocks, sold at stone yards and home centers, have a rough face for a quarried look and come in a variety of gray, tan, and red hues. Like timber and dry-stacked stone walls, they rest on a crushed-stone footing. Heavy-duty mesh anchors every other course against the ground.
Cost: Versa-lok Weathered Mosaic (shown), $11.40 per square foot uninstalled; Versa-Lok
Reader Mike Sieber of Mannington, West Virginia, stacked large stone blocks to level off a steep decline and make distinct areas for entertaining and game-playing.
Readers Dominique and Eric Butters of Silver Spring, Maryland, cut into the slope behind their home, lined the ledge with interlocking concrete blocks, and gained a patio with a sitting wall.
Reader Sandra Yoshioka of Torrance, California, used stuccoed-block walls to create a flower-filled buffer between the sidewalk and her front door.
Reader Clifford Parker of Jamestown, California, raised the grade in his yard and built a hybrid stone-and-timber wall to hold up the outer edge of a new gravel drive.
Smooth away the blahs, and any surface blemishes, with a coat of cement-based stucco. When tinted or painted an earthy shade, stucco will also complement your landscape.
Shown: Quikrete Finish Coat stucco in Palomino, 21 cents per square foot.
Give interlocking blocks a makeover with a penetrating finish in a warm reddish or golden hue. Water-based stains can be applied with a sprayer or roller directly onto a clean, unsealed surface.
Similar to shown: Rust-Oleum concrete stain, 15 cents per square foot.
To enliven a bland surface, adhere thin slices of brick or stone, or concrete molded to mimic stone or brick. You get a traditional look for less than the cost of regular mortared masonry.
Shown: Natural Stone Veneers, Tuscan Collection, starting at $8 per square foot uninstalled.
Only a structural engineer or mason can say for sure, but if yours shows any of these signs, it may be time for a new one.
Walls like the one shown, that slant noticeably are not long for this world. Whether it's caused by tree roots, poor drainage, or a failed footing, a leaning wall will probably have to be demolished and rebuilt from scratch.
You can fill minor blemishes in poured concrete with hydraulic cement. In a mortared wall, simply chisel out damaged joint filler and repoint. But if the cracks are more than ¼-inch wide and deep, and more than 2 feet long, the wall may have structural damage. Call in a pro to assess whether the affected area can be repaired or has to be replaced.
A pronounced dip in the courses of a timber or interlocking block wall indicates that the footing has failed in one spot. A pro may be able to replace the footing beneath the damaged area and rebuild just that section of the wall.
When mortared masonry develops a pot belly, the likely culprit is a buildup of water pressure behind it. Try drilling a ½-inch weep hole with a masonry bit to encourage drainage. A bulge in a timber or interlocking block wall is typically caused by a lack of anchoring. Careful excavation behind the wall may allow a protruding section to be rebuilt. Consult a pro before starting work.
Use plants to soften a rugged expanse of masonry. The next 8 slides show some colorful perennials that will clamber up the face or hang over the top of your retaining wall.
Shown: Japanese garden junipers
Low-growing Japanese garden junipers tumble down a mortared-stone wall.
Rooted along the base of the wall, these plants grow up in search of sun. Most benefit from a trellis to help get them established. You can usually remove the support after a year or two.
Shown: Climbing Hydrangea (Hydrangea petiolaris)
Clusters of fragrant white flowers stand out from this vine's heart-shaped foliage in summer. Grows up to 80 feet high and 12 feet wide in Zones 4 to 8.
About $25; Wayside Gardens
Planted on top of a wall, these plants spill over the edge for a dramatic, cascading effect. They all do well without supplemental watering, which can increase soil pressure on the wall.
Shown: Fairy rose (Rosa polyantha 'The Fairy')
This disease-resistant rose has shiny green leaves and profuse pink clusters of summer blooms. Grows up to 3 feet high and wide in Zones 5 to 9.
About $25; Moody's Nursery