Segmental Retaining Walls – what is behind the wall

Posted in Masonry, Pavers, Uncategorized, Winter Landscape at 6:10 AM by Administrator

We have found that segmental retaining walls benefit (last longer) when the walls are built with an adequate drainage behind the wall.  As such, we follow the rules of the NCMA on how to build a segmental retaining wall.  Behind every wall, there needs to be adequate drainage and this drainage area is achieved through backfilling with 3/4″ crushed stone.  The crushed stone provides stability while allowing water to move freely in this area and not cause pressure onto the back of the retaining wall.  We also use a layer of fabric to separate the existing loam from this drainage stone.

In some cases, a geo-grid is required to provide additional support for the wall.  We recommend discussing the appropriate way to build a wall with an engineer or experienced installer as they can determine the need for geo-grid.  In this case, we included geo-grid in the wall construction because the existing soil has a high clay content which might result in more pressure against the back of the stones than we like.  We backfilled a couple of layers of wall stone and then installed a layer of geo-grid and in some parts of the wall where we were concerned with the amount of pressure coming from behind the wall, we installed a 2nd layer of geo-grid.

Newton Wall In-process - Drainage installed and Filter Fabric

As the crushed stone was used to backfill, we ensured that the drainage pipe was still sloped at the right pitch to help carry water out past the wall.  We made the layers of geo-grid tight before continuing with backfilling.  This picture shows how the geo-grid needs to be (fully extended and taut) before backfilling on top of the geo-grid and wrapping the whole drainage area with soil stabilization fabric prior to finishing the area with freshly screened loam.

Newton Wall In-process - GeoGrid installed

Please contact Tony at 978.948.2900 or visit our website at www.Artistic-Landscapes.com to talk with us about designing and building your retaining walls.

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