How high can retaining walls be built?
The simple is you can build a retaining wall that is less than 4’ without a permit or engineering, and almost as high as needed with professional engineering and a city permit.
There are some caveats though! To fully understand how high you can build a retaining wall, we need to understand 3 main factors.
The 3 main factors are city building requirements, the type of soil on site, and the retaining wall block manufacture specifications.
Most cities in the Fraser Valley allow walls under 3.9’ to be built without a permit or engineering.
If the wall is over 3.9’ a building permit and engineering are required. Some cities also have a bylaw stating that you can’t build a large wall if it doesn’t fit with the neighbourhood.
The 2nd factor is the onsite soil type. Soils that are heavy clay retain water, and are very heavy.
This may mean that structural precautions and overbuilding may be a really good idea, even on a smaller wall under 4’ in height.
You may want to build a wall to an engineered standard even if it is not required.
The 3rd factor is closely related to the site soils. Manufactures like Allan block have a chart that says the wall height for common applications.
These wall heights can be as low as 13” tall when they start to require additional structural components.
To summarize, there are a lot of influences and factors that set the maximum wall height.
Some retaining walls can be simple and built to a height of 4’, while others will need some structural support for walls that are only 13” tall.
For every retaining wall you should at least consider what forces will be applied to this wall, as it will need to stand up to them for a lifetime.