Having a retaining wall installed, whether it be to serve a purpose (such as retaining soil) or to add some depth to your landscaping, can be a huge undertaking. One main factor that comes up in a retaining wall build, is what is this project going to cost me?
A typical retaining wall will cost between $10,000 and $50,000
The reason the price range is so big, is because not all walls are built alike. Materials, quality, equipment, site access, and what your yard looks like, all factor in to the price of a retaining wall build.
Here are two examples of why the price range for a retaining wall varies.
#1 Structural Retaining Wall 25’L x 3’H high built to Allan Block specifications.
For a 25’ x 3’ Allan Block retaining wall expect to pay between $12,000 - $15,000
For this price you can expect your driveway and lawn protected or remediated afterwards from heavy equipment, a structural retaining wall built to last a lifetime, and of course a fully insured, licensed and reliable construction company handling your project.
What is typically included when building a retaining wall?
- Creating an excavation ticket with BC1CALL
- Protecting concrete areas and lawns
- Excavation of the site
- Hauling/disposal dump truck & trailer of soil
- Hauling and importing gravel to build site
- Building the gravel wall foundation
- Construction of the wall
- Drainage system tied into existing source
- Backfilling and compaction behind wall
- Site clean-up, lawn repair if damaged
What could drive the price of a retaining wall higher?
- Limited space that doesn’t allow heavy equipment or material stockpiling
- Any demolition of an old wall, fencing, or landscape
- Structural support design for fencing installed near any part of the wall
- Working around detailed landscaping that needs to be fixed afterwards
- Protecting surfaces in excess of 100’ (laying down plywood to drive on)
- If preventing damage is not practical then thorough remediation after project is complete
- Buried and unexpected finds underground (although rare its worthy of a mention)
- Soil conditions: Geogrid may be required for walls higher than 13” in clay soils
- Length or complication of tying drainage system into appropriate source (storm drain, sump basin etc.)
What could drive the cost of a retaining wall down?
- Wide open site allowing bigger or more efficient equipment
- No existing wall requiring demolition
- No fencing in or around retaining wall
- No detailed landscape in front or behind wall
- Not needing surface protection
- Wall being built prior to finished landscape, and not have to tidy up from wall construction
- No excavation surprises
- Soil conditions: Water permeable soil that reduces the need for Geogrid, or as much gravel as normal
- A nearby drainage system that can accept the water from behind the wall
# 2 For a 75’ x 6’ high Allan Block retaining wall expect to pay between $45,000 - $49,000 including permits and engineering
While this wall is subject to much of the same factors as the smaller wall, we need to point out some pretty substantial differences.
Somewhat confusing is the maximum wall height before needing a permit, engineering, or Geogrid. It is most common to think that over 4’ you must meet these 3 requirements. The truth is, this is not entirely accurate.
A gravity wall is defined as a wall without reinforcement such as Geogrid or No Fines Concrete. A wall as low as 13” could require reinforcement, while in another scenario a maximum wall height of 9’ 8” could be built without any reinforcement.
Separately most cities require a permit and structural engineering on any wall over 3.9’.
The requirement for reinforcement or permits and engineering is independent of each other. Its variables like these that make taller walls a little more complex.
The exact cost of these engineered walls will vary, as engineers take into account the exact site conditions which will include slopes above or below the wall (a land slope analysis may be required), soil structure, location of wall on property, and other factors.
For the permit, and typical Engineering expect to pay between $3600-$5000
The last substantial difference in a small wall vs a larger one is the drainage system.
A wall that requires reinforcement such as Geogrid automatically requires a 2nd system called the heel drain. This drain captures water further away from the wall, and lowers the surcharge on the wall.
There are a lot of variables when designing and building a concrete retaining wall. In every case their job is to hold back a lot of weight for a lifetime. While you should never go into debt to do a project like this, keep in mind that you do pay for what you get, and if your wall is done right the first time around, you can avoid a huge headache of having to get it redone.