Designing your retaining wall

Offering reliable landscaping services to homeowners in British Columbia since 2013

Picture of Sam Maerz

Sam Maerz

Owner/Site Foreman

The majority of your retaining wall design will come from your ideas, and your contractor’s vision.

Allan Block retaining walls have their own unique requirements ,so you will have to rely almost exclusively on your contractor’s knowledge. Their knowledge will either make or break your project.

An example of this would be you need a drainage zone behind your retaining wall, so you cannot put the wall right at the property line, it needs 12” of space behind it on your property.

Another example would be if you’re replacing a wood retaining wall. The wood may be 4” wide, while an Allan block is 12” deep. The physical dimensions, are different than wood and this must be taken into account for.

There are solutions to every scenario though, and this is what makes Allan Block the most versatile retaining wall block.

Pro tip:  Caps are not always required. Plants or grasses can overspill the front of a wall, and create a very natural look.

retaining-wall-natural-plants

Engineered Retaining Walls 

 Engineers play a vital role in designing what we call reinforced retaining walls.

Reinforced walls are those that include upgrades to make a normal “gravity” wall stronger. This includes Geogrid, no fines concrete, or other less commonly used methods.

While Engineers understand the physics and mathematics very well, there is an element to building walls that one must learn from building walls.

Ideally your builder will work with the engineer to improve the design right from the beginning, and throughout the project.

A city building permit, along with an engineered set of drawings, are legally on retaining walls over 4’ in height in all of the municipalities in the lower mainland.

On top of the cost for the drawings, and city permit, expect to pay for 3-6 site visits by the engineer, and “memo’s” written for WorkSafeBC stating the safety concerns, and safety guidelines on site.

Usually, the city will do 2-3 site visits to inspect the property prior to construction, a plumbing inspection for the drainage system, and a final inspection confirming the wall was built as per the drawings.

 

Surveyors

Surveyors are responsible for confirming property lines, and can also provide the elevations of the property.

This is useful for determining the exact heights needed to be retained. 

Property lines must always be established prior to the building of any retaining wall. Allan Block recommends this is the property owners’ responsibility.  

 

 

Field Fit

Every retaining wall will be subject to what we call a “field fit”. This refers to an onsite reality check, when reality meets a drawing on the paper.

This is unavoidable, and common on walls that have access issues, extreme elevations, or just for basic design improvements.

Usually as you build you come across a challenge, and then you have to decide which of 2 or 3 choices are optimal.

Every problem most likely has several solutions all which have pros and cons!

We are fortunate to have a great relationship with Bruce Stickney who is our technical rep from Allan Block.

He is quick to answer calls, jump on a video call so he can see what we see, or come out to the site.

Every retaining wall project we work on Bruce has input before, during or after. He constantly challenges us to be better, and provides coaching after every project. He’s a true mentor.