Landscaping with concrete
The American Landscape is rugged. Retaining walls are a powerful landscaping tool to deal with elevation changes, where the resulting slope would be too steep. These can be found in practically every city in America, and Portland is no exception. There are many types of retaining walls, and these can be built out of many materials. One of the better ones is concrete, both for functionality and affordability.
More than Meets the Eye
Retaining walls are simple enough structures. They are basically walls that support the mass of the ground above them. Given the complex ground dynamics that are in play, theses structures need to be carefully constructed by a professional contractor.
In fact, the City of Portland requires a building permit for any retaining walls above four feet, or those with large surcharges.
A common mistake is to build many small Concrete retaining walls instead of a single one that is taller. This is terracing badly applied. Some contractors do this to avoid obtaining a permit from the city. However, building a second concrete Concrete etaining wall above or near the first one, simply increases the surcharge.
The surcharge is the force that the terrain above the structure will exert on it.
For example, if you build a driveway above a Concrete retaining wall, the weight of the driveway needs to be taken into consideration, otherwise it could collapse.
One of the main reasons retaining walls collapse is failure to use geogrid and correct draining aggregates. If the structure has nowhere to drain, then all of the water will accumulate near the wall and eventually it will bulge or crack.
When it comes to retaining walls, investing in quality now will save you a lot of headaches in the future.