Building a Wall Step 1:  Determining Structure
(Understanding What Kind of Wall You are Trying to Build)

You want to build a wall to enhance your outdoor living environment.  The first step is to determine the structural needs of your wall.  It is the structure that dictates your construction technique, what construction materials and tools you need, and, perhaps most importantly to your finished project, what wall products you can successfully use.  The appearance of the finished wall will be determined by the wall material you choose.  The issue of appearance, i.e., style, texture and color for your finished wall, will be covered in a separate article:  Building a Wall Step 2: Look and Feel.

There are three major types of wall structures:
1. garden walls
2. retaining walls
3. sitting walls.
The fundamental differences in these walls are their height and what is behind them.

A Garden Wall refers to a wall designed to define an outdoor area such as a flower bed, a tree, a mailbox, a lamp post.   No higher than 18 inches, a garden wall generally holds in soil and may be topped off with mulch or decorative stone.  With a garden wall, you create a raised area that becomes a softscaping environment filled with whatever you want to create the visual impact you envision.  Options to complete your garden wall project include plants, boulders, statuary, fountains, birdbaths.

Literally any wall block or natural stone can be used as the garden wall has the least demanding structure.  Although any wall product is technically acceptable, the most common materials are small wall blocks or stacked natural stone.  Manufactured garden wall blocks include Coventry Garden Wall from EP Henry and Manchester from Techo-Bloc.  Most garden wall products are approximately 4” high x 12” long x 8” deep.   There may be a lip on the back of the block to lock each course as you build it up but many are simply stacked and held in place by weight.  Garden Wall products can not be safely used in either retaining wall or sitting wall applications. If the garden wall requires a greater height than 18 inches, products classified as garden walls can not be used as designed and you must use retaining wall construction techniques.

Retaining Walls are structures with the specific requirement of holding back large amounts of soil and/or rock.  Retaining walls are 2 feet up to literally as high as needed.  Commercial walls, e.g., the walls you see along the highway or around a shopping center, can be amazing heights.  Situations where a residential retaining wall (also known as an SRW) is necessary include:

• building a wall to eliminate a sloped back yard and create a large flat yard for outdoor activities or a patio or other outdoor use
• building a wall to protect your driveway by holding back soil that slides onto a driveway from a yard that is significantly higher than the driveway
• building a garden wall around the side of the house where the front yard is higher in the back yard so that the wall may be only 15” high in front but becomes over 2’ in the back
• building a wall to surround a walk-out basement

Retaining walls fall into two categories:  gravity walls or engineered (reinforced) walls.  Engineered walls require multiple skilled professionals to be safely executed.  A professional hardscaping contractor should be hired to build this type of wall as he or she will have the capability to arrange the technical resources needed for projects of this scale.  Gravity walls can be safely built by anyone willing to take the time to learn how.  Retaining walls can be build from manufactured segmental retaining wall block, stacked natural stone or boulders, and other construction materials such as Gabion baskets; however, very high walls require a suitable segmental retaining wall product.

A huge range of manufactured products are available to construct retaining walls (also known as SRWs).  Not all products are suitable for all heights and all applications.  Examples of SRWs suitable for modest height gravity-based SRWs include EP Henry’s Terrace Wall and CST’s Versa-Lok Mosaic.  These products are at least 8” in depth and 6” in height and feature some locking mechanism Examples of SRW’s suitable for large scale gravity-based or engineered SRWs include:  Diamond Pro from EP Henry; Suprema from Techo-Bloc; and Versa-Lok from CST.

Sitting Walls are structures used to create a free-standing wall that can be used like a bench or for privacy.  Typical applications include:

• Creating a sitting area on a patio or pool deck
• Creating a boundary between two residences that are close together
• Creating an outside perimeter on a raised patio to protect from falls
• Creating an alternative to a railing on steps

Each sitting wall product has a maximum height which is usually between 24 and 36”.  Sitting wall products are the most expensive manufactured products due to the requirement for them to appear identical when viewed from either side.   Examples include: Mini Creta Plus from Techo-Bloc, Double-sided Coventry Wall from EP Henry, and Veranda from CST.

Please see separate articles (Building a Wall Step 3) on the construction of each of these wall types.