Keystone Retaining Walls

Engineered systems like these keystone retaining walls are giving homeowners the ability to create imaginative landscaping that's very strong and durable. Best of all, these systems are practically maintenance free.

When you think of what it takes to create a beautifully landscaped yard, you probably don’t think of fiberglass  and concrete, but these days, that’s often exactly what’s involved. Keystone engineered retaining walls are giving homeowners the ability to create imaginative landscaping that’s very strong and durable. Best of all, these systems are practically maintenance free.

Building your own Keystone retaining walls is as easy as four simple steps:

Preparing the site
   1. Start by digging a shallow trench 4" deep by 12" wide.
   2. Cut through and remove any sod, roots or large rocks.
   3. For organic loam soils, dig 4" deeper and add a leveling pad of sand or gravel.
   4. Now compact and level the soil to receive the first course of landscape units.

Setting the base course
   1. Place and level the first unit with the retaining lip down.
   2. Level each additional unit as you place it, making sure that the outside edges touch.
   3. If your wall contains both straight and curved areas, start with a straight area and build into the curves.  Complete the base course before proceeding to the second course.

Inserting the interlocking fiberglass pins
   1. Place the reinforced fiberglass pins into the holes of each two Keystone units.
   2. Once they’re in place, the pins create an automatic setback for the additional courses.
   3. For near vertical setback, place the pins in the front holes.
   4. For 1 1/4" setback per course, place the pins in the rear holes.

Stacking and filling
   1. Starting with straight areas first, begin placing the second course.
   2. Center each unit on the seams of the course below in a running bond pattern as shown.
   3. To maintain proper spacing on curves, remove the outside edges of the retaining lip as required.
   4. Now proceed to the next layer, backfilling as you go.
   5. For drainage behind the wall, clean gravel or crushed stone is recommended.

Remove outside lugs or edges of retaining lip
   1. Hold unit securely or place at angle on ground.
   2. Strike the lug firmly with a hammer.
   3. Always wear safety glasses to protect eyes from chips.

How to figure how much setback there will be per course
   1. Level three units side by side and install the pins in the preferred set of pin holes.
   2. Set the next course of Keystone units on the three you just leveled and slide them forward toward the wall face so they are in full contact with he pins.
   3. Measure the distance the second course tails are overhanging the units below.
   4. This will give you your true setback per course.

Where should you begin building a retaining wall?

Construction of the wall should begin at your lowest point whenever possible.  If the wall is going to tie into a building or structure, measure the distance from the corner of the Keystone unit to the edge of the building and make sure the distance is in an increment of 18".  (Full unit width.)

What size rock is best suited for filling in and around the Keystone units in the drainage zone?

A clean, angular 3/4" rock is best for unit drainage fill. Otherwise, use a clean rock material that is 1/2-1-1/2" in diameter. Avoid aggregates that are round in nature. Angular material will provide the best interlocking strength. Also avoid material that contains a lot of fine grains in that these fines can flow with water through the wall resulting in settlement and possibly staining the wall face.

How much rock do I need to use?

Adequately fill all open cores and 12" behind the unit when using a Keystone Compac unit.  The additional rock behind the unit provides better drainage and eliminates the need for compaction equipment directly behind the wall.  For Keystone Standard units, drainage fill needs only to be placed in all open cores approximately 2' (600mm) back from the wall face.

What advantages are there to using a pinned system?

Unlike other retaining wall products, Keystone's pinned system offers the choice ofnear vertical or one inch setback options.  It allows you to achieve tight corners and curves automatically without having to cut units while maintaining the running bond pattern.  The Keystone fiberglass pins also provide additional shear strength at the wall face and positive connection with geogrid which allows proper pre-tensioning and resistance to bulging during construction.

How high can Keystone units be stacked before placing unit drainage fill and backfill?

Keystone recommends adding drainage fill and backfill after each consecutive course for its Compac units.  This insures that all voids are properly filled with rock providing maximum interlocking strength.  It also aids in keeping the wall straight and reduces the amount of wasted rock.

Note: Because of the depth and size of open core areas on the Keystone Standard units, The Standard units can be stacked up to a maximum of 2 units before placing unit drainage fill and backfill.

What type of material should be used to backfill?

Granular materials such as rock and sand are preferred.  These types of materials compact fairly easy and won't hold moisture that can increase the weight of the soil behind the wall.  Keystone walls can be effectively built with salty material and lean clays, but these types of soils require more compaction and care should be taken not to place these materials when they are wet.  High clay soils that shrink and swell rapidly as well as organic soils should be avoided.