As retaining wall contractors who have been in business for many years, we have encountered nearly every situation that could come up. Because our region is so hilly, retaining walls are common across all types of residential and commercial properties (so we stay pretty busy)!
Many times with new residential and commercial development comes the need to build new retaining walls to support the project. However, there is just as much need to repair or replace existing walls that have deteriorated over time. Old walls that are falling apart could become a safety hazard and should be replaced as soon as possible.
Without a doubt, the combo-question I get asked most is…
How much does a retaining wall cost and what kind of retaining wall can I install?
Customers and potential customers alike are almost always amazed at the cost of landscape work in general and retaining walls in particular. Cost is not just about the materials used for the project; it is also a function of the time involved in the design and installation. Labor is the key component of any construction project and any contractor building a retaining wall has a large labor cost.
But it isn’t just limited to retaining walls. Labor costs are a big part of pretty much any service you have someone perform. Have you ever checked the invoice whenever you have work done to your car? Take a look next time; the cost for the parts is usually a fraction of the labor cost.
The second most asked question is one that continues to evolve.
Not too long ago, when a customer wanted a retaining wall installed at their residence, the choice was simple; get stone or railroad ties. That is certainly not the case today. With new materials come many new options. And which wall type to go with requires some thought.
Before starting your project, consider these tips when thinking of installing a retaining wall in the Pittsburgh area:
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 Versa Lok, Keystone, 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. Not all materials work equally well in every situation, so design will dictate what material(s) could be used.
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 2-10x that of dry-laid walls.
Before you get started on a retaining wall project, be sure to take the above into consideration. This will help you plan accordingly and will probably lessen the sticker shock from the project bids.
If you have any other questions, please feel free to contact us and we will be happy to answer all of your questions.