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Extension > Garden > SULIS > Implementation > Natural Stone Retaining Walls

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Natural Stone Retaining Walls

Chris Matson

Description/Purpose:

Natural stone walls are retaining walls constructed from cut stone without the use of mortar or other adhesives to hold the wall in place. Instead, the wall is held together by friction and the weight of the stacked stones (Homestore.com, 2000).

Image 1
Kallin Johnson, 1997, Granite blocks
www.kjgems.com/granite_products.html

Natural stone is a popular alternative to the traditional modular cement block for retaining wall construction. Dry-stacked, natural stone walls add a very natural look to any landscape as the material is taken right from the ground. Natural stone walls allow water to flow freely behind and through the wall thus relieving a significant amount of pressure on the wall.

Amount/Specifications:

Tools, Supplies and Equipment: Step-by-Step Process:
  1. Using the tape measure, string line, stakes and marking paint, measure and lay out the wall. Use the string line and stakes to mark off any straight portions and the marking paint to draw out any curves. As curves become tighter, smaller stone will be needed. It is best to keep curves as large as possible.

    NOTE: When curved walls are desired, is important that the curves be as large as possible to eliminate jagged curves. Additionally, smaller pieces should be used around curves. Larger pieces will create flat spots on the curve and the set backs from one course to the next will not be even.

  2. Dig a trench that follows the string line and/or marking paint. The trench should be 1 foot deep by 6 inches wider than the stone. For instance, if the stone selected is 8 inches wide, the trench should be 12 inches wide and 12 inches deep.

  3. Fill the trench with 3-4 inches of crushed limestone. Make sure that the limestone is roughly level and compact it thoroughly with the plate compactor. Add another 2 inches of crushed limestone on top of the compacted limestone

  4. Begin leveling the base course of stone by placing a stone on the crushed limestone. Check for level front to back and side to side and adjust accordingly with the large mallet. Due to the nature of the material, the stone will not be perfectly level, but it is possible to be very close. Once the first stone is level, continue along the trench making sure each new stone is level with the preceding. Use the string line again to make sure the straight sections are straight.

  5. If the wall is going to be larger than 3 feet high, perforated drain tile should be placed behind the base course and then buried by the drainage aggregate. An illustration of drain tile may be found in Step 7 of this report of Step 6 of Installing Block Retaining Walls.

  6. Next, stack the second course on top of the base course. Make sure the seams between the stones do not line up from one course to the other. Also, pick stones that fit well with those on either side. If there are large gaps, it may be necessary to use the stone splitter to get a more snug fit. Additionally, each course should be set back at least 3/4 inch to allow the wall to lean back into the ground that it will be retaining. Oftentimes the stones will not lay perfectly level on the preceding course. It is then necessary to shim the backs of the stones to eliminate wobbling. Shims are small flat chips that break off the stone when they are split.

    Drawing 2

  7. After two or three courses are stacked, backfill the wall with the drainage aggregate. To do this, lay the geo-textile fabric on the soil behind the wall, and dump the drainage aggregate between the wall and the fabric. The aggregate should be at least 8 inches from the wall to the fabric. Compact the aggregate thoroughly with a shovel or large mallet. It may be necessary to fill dirt in behind the fabric as the stone is added.

    Drawing 3

  8. Continue to alternate stacking 2 or 3 courses and backfilling the wall until the wall is complete.


References:

Blue Mountain Building Stone Company. June 2002. http://www.bluemountainstone.com

Brett Nutting. Vice-President JLM Landscape. Feb. 20, 2001. Interview

Buechel Stone Corp. 1998. Pamphlet

Dixie Stone & Marble, Inc. 1999. "Landscape Stone."

Homestore.com. 2000. "Building a Dry-Stacked Stone Wall."

Kallin Johnson Monument Co. 1997. http://www.kjgems.com/

Vengeance Creek Stacking Stone. 1998. Product Listing. http://www.vcstone.com/information.html


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