Retaining walls are major investments. Understanding common mistakes before hiring a landscaper (or doing it yourself) is wise. Here are few of the common mistakes we see:
Built too high relative to surrounding grades
Retaining walls should be buried into the ground so soil covers the a portion of the face. This soil in front of the wall prevents the lower courses from blowing out. The amount of buried wall varies depending on the material type but should generally be at least 6" for any wall over 18"
Inappropriate drainage behind and around walls
Good drainage is necessary for the long-term stability of the wall. Drainage material behind a wall that reduces hydrostatic pressure and expansion during freeze thaw is critical. This is generally accomplish with clear stone (free of fine material) and a perforated drain pipe to capture and conduct water away. We also utilize geotextile fabric behind our clear stone to keep it separated from surrounding soils. In terms of grading in the area of a retaining wall, stormwater should ideally be conveyed around walls by uphill grading rather than expecting a wall to function as a dam.
Joints the align vertically
When building any wall it's advisable to build it as strong as possible. In order to do this it''s important to limit the number of uninterrupted vertical seams. The old saying is "on over two, and two over one". All joints between stones should be fully covered by the stern above with a good amount of overlap. This is something every kid learns playing with legos but somehow landscapers can't seem to get it right.
Walls should be built with each new course a bit staggered back from the previous course so the wall is not vertical. This is called a walls "batter." This reduces the chance a wall will tip forward over time.
Lack of Reinforcement
Timber walls should have "dead men" which are "T" shaped reinforcements buried into the area behind the wall. Block and stone walls often need a geogrid reinforcement to tie them into the surrounding soils once they are over 3 or 4 feet in height.