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By Melissa Erickson
Retaining walls can be a big investment , but they don ’ t have to be merely barriers that hold back soil . With good design , they can help create beautiful outdoor spaces , too . Considering a retaining wall ? There are many factors to think about , including when to call in a professional . “ Retaining walls are hardworking structures that fight a constant battle against gravity , so consider many variables when developing them ,” says Christina Hebb , a soil scientist with Duraroot . Questions to consider include :
• Is the slope steeper than 3 to 1 ? That means if the change in height is three times the change in horizontal distance , the job requires a professional .
• Will the retaining wall have to endure frost and freezing ?
• What is the drainage like ? If water will flow heavily on the wall
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Retaining walls can have both
“ You may need a professional to help you to assess the soil in the area you plan the wall . Also look at the climate and terrain — this will help you know if this is a weekend job for you , or whether you need professional help .”
and soil , you may need to add drainage .
• What ’ s the soil like ? A soil with a heavy clay content will not drain well , but is also less prone to erosion . For sandy soil the opposite is true .
• Are there other structures nearby , and what influence will the wall have on them ?
• Do you live in an earthquakeprone area ? If so , an earthquake engineer may need to analyze the wall to make it more resistant . “ You may need a professional to help you to assess the soil in the area you plan the wall . Also look at the climate and terrain — this will help you know if this is a weekend job for you , or whether
– Christina Hebb , soil scientist , Duraroot
you need professional help ,” Hebb said . Usually thought of as only used for soil retention , retaining walls serve multiple purposes . “ If placed , designed and installed properly , retaining walls are a perfect way to improve the landscape design and prevent landscapes from sliding or flooding . Additionally , retaining walls can be placed just about anywhere to expand the usable space in an area and create a focal point on your property ,” Hebb said . There are four basic types of retaining walls :
• Gravity walls hold in earth by the weight of the wall material . They could be a stack of large rocks , or more formal like pavers . They can fail easily , and should be used only for short slopes — 3 feet or less .
• Piling walls use long “ piles ” — or poles — that go deep into the soil as well as above it . The pilings can be made of metal or treated lumber . They have a good capacity to hold back the soil .
• Cantilever walls are similar to piling walls . However , they get added strength from an “ arm ” that extends back into the hill , increasing their capacity to stabilize pressure .
• Anchored walls are the strongest type of retaining wall and can be combined with other techniques . As the name implies , an anchor is wrapped around the wall and has a base deeper into the hill , which provides the stabilization . “ The best materials for the job depend on the function , cost and height of the retaining wall . Retaining walls for only decorative purposes can use any type of material that the owner likes . Retaining walls that will support a large load — providing a structural purpose — require durable , long-lasting material suited to the site conditions ,” Hebb said . If you ’ re not sure you ’ re up for the job , consult a construction landscape contractor . “ Be sure to hire companies who are licensed or certified in the area ,” Hebb said . ❇❇
14 • 2017 Fall Vermont Home , Garden & Car