Death of the Windsor Retaining Wall

Death of the Windsor Retaining Wall

Suspicious Water Fountain! No thanks!
Source: Flickr

My father asked me the other day, what question did I get most from my landscape and lawn care customers. The answer: How much does it cost and what kind of retaining wall can I install?

Customers and potential customers alike are always amazed about the high cost of landscape design. Cost may not always be about the materials used, but it is always, about the time involved in the design and installation. Labor is the key component of any project and any business. If you doubt me, just call for an estimate on an in-home computer repair.

The second question is one that continues to evolve. Not long ago, when a customer wanted a retaining wall installed at their residence, the choice was simple; you get pavers or Windsor’s. That is certainly not the case today as Windsor’s are rapidly becoming extinct as the dinosaur. Here are few tips when thinking of installing a retaining wall:

1. Materials: When choosing materials, select the type that is best suited for the desired result. Many long-lasting materials are available for landscape use including flagstone wall rock, Xeriscape rockery, railroad tie maze, regal stone, Pyzique stone, Windsor stone, and framed fence. Also consider recycled concrete paving treated timbers, vertical poles, pre-cast concrete modular units, poured concrete, and brick veneer.

2. Type of wall: The type of wall you choose should be determined by need. Decide if you need a poured-in-place concrete “structural” wall or a much less expensive “dry-laid wall” consisting of stacked, open-joint material.

3. Determine design or on-site placement: Planning ahead will help you avoid the expense and time it takes to relocate a wall or to modify retained areas once they’re installed.

4. Drainage: Most retaining walls fail because of pressure against the wall caused by water or soil-moisture build up behind the wall. All walls should provide for the back-of-wall water to freely drain down and away from the wall. This is accomplished with gravel backfill, or manufactured drainage blankets and drain pipes. Structural walls require “weep” holes to allow water to drain from behind the wall.

5. Foundations: A wall is only as good as its foundation, and all retaining walls should be built on structurally sound, compacted foundation sub-base material. Leveled and compacted earth or gravel fill are acceptable. The foundation material should extend at least one foot beyond the front and back of the base width of the wall. When building dry-laid stone walls, place the largest, most stable stones on the bottom of the wall, and be aware that the base width may need to be as wide as the wall is high.

6. Cant or batter: Walls are more stable and structurally secure if they slope back or “lay back” into the retained slope. This amount of variance from true vertical is called “cant” or “batter”.

7. Anchors: Timber walls and other walls of solid horizontal materials usually have “T” anchors extending back into the slope into undisturbed earth. This helps walls resist pressures that force them forward, or cause them to pivot on footing material. A good rule of thumb is to provide at least one anchor per 16 square feet of exposed wall face.

Installed wall costs generally range from $20 to $35 per square foot of wall face for dry-laid materials. Cost will vary considerably depending upon materials used and overall wall height. Structural wall costs may range from two to ten times that of dry-laid walls.