Retaining Wall Engineering and Permits

Understanding when retaining wall engineering and permits are required can be a little confusing. Keeping this in mind I’ll do my best to explain the differences, and the factors involved.

Engineering is basically a reinforced retaining wall designed by a structural engineer.

Municipalities require permits on retaining walls when they are higher than a certain height. Typically, this is 4’ in height, but in cities like Mission B.C this is closer to 2’ in height.

Permits always require engineering, but engineering doesn’t always require a permit.

For instance, in Abbotsford B.C the maximum height you can build a retaining wall without a permit is 4’. If you build a 3’ high retaining wall you would not need a permit. However, if you had an additional weight surcharge on top of that wall you may want it designed by a structural engineer to ensure the retaining wall can handle that.

A Deeper Dive Into Engineering For A Retaining Wall

An engineer will design a retaining wall and take into account the sites soil, elevations, and use.

Engineering includes drainage details.

Once designed the engineer conducts computer simulations for earthquakes and environmental possibilities (overturning, sliding, etc.)

Drawings are never final as field fit will ultimately change the design several times.

Most retaining wall builders will only work with their engineer, as this relationship is key to a successful project.

Engineers are not installers, and installers are not engineers, yet both parties need to be comfortable and happy with the design.

For projects over $100,000 the engineer will also issue a “Memo” for WorkSafe BC stating site conditions and safety protocols.

Engineering costs will change throughout the project as designs are updated and expired WorkSafe memos are renewed. Expect to pay between $5000-$15,000 for engineering with all the site visits by the engineer.

An additional cost that may be required and is definitely a good idea is a site survey. This marks the property lines, and provides the engineer with detailed elevations. This cost is in the ballpark of $2500-$5000.

A Deeper Dive Into Permits For A Retaining Wall

The permit process will vary by the municipality, but here is a rough overview.

Cost is typically a percentage of the project cost, and ends up between $200-$1000.

Permits require engineering so there will be a period of time before the engineering is complete, and then your wait for permits starts. There are a lot of time factors, but expect to wait 2-4 months before we can start construction.

A retaining wall permit will also require a plumbing permit for the drainage detail.

Permit inspections vary by the municipality, but expect a few site visits and onsite work delays while waiting for city approval to continue construction.

OF NOTE*

An engineered retaining wall is not built the same as a small gravity RW. As well as the costs for engineering and permits there will be considerably more costs associated with building the wall with reinforcements. This means more excavation and soil removal, more gravel placed behind the RW, and the installation of Geogrid (a structural netting that combines the wall and gravel together as one unit).

Summary

All retaining walls should be built by a trained, certified, and experiences retaining wall builder. This is even more true the bigger the retaining wall. Every engineered retaining wall we have built, we have made several changes to the engineered drawings prior to even breaking ground. If you want confidence in your retaining wall project let us take ownership of it.