I have seen many garage wall failures due to poor design. The problem typically is the foundation contractor constructed the garage wall using the same configuration and reinforcement used in the adjoining basement wall. The problem is the garage wall retains fill material and has a surcharge (Car and garage floor slab) pushing on the garage wall. The garage wall should have been designed and reinforced as a cantilevered retaining wall. The photos below show a tall rear garage wall on a foundation built on a steep hillside. The internal pressure cracked the wall in the middle and eventually pushed the garage wall out about 1-inch where it joins the basement wall. I also included two 3D Graphics comparing a Basement Wall to the proper Retaining Wall. Both have 8 inch walls, however I designed the footing size and reinforcement to hold back the pressure. Notice the footing size difference and the amount of reinforcing steel needed versus the standard basement wall.
Nice, thanks Randy.
Randy, isn’t an engineer supposed to design the foundation (footing, reinforcement, wall thickness, etc…) to accommodate such a high wall with nothing on one side of it? Should it not be on the plans and be approved by an engineer? why is the foundation contractor not following the design plan?
Just curious, should there also be some type of an expansion joint that separates the garage from the retaining wall or is that not needed
Excellent as usual Randy !!
A lot of times an architect prepares the plans. This is what happens when foundations and structures are left in the hands of an architect who is out of his lane.
Gary, the graphic is split in the middle for comparison only. I would dowel in the retaining wall to the basement wall, most garage walls are typically less than 30 feet long. A really long retaining wall like you would see along a highway would require expansion joints like any other long masonry wall.
Darren, you are correct if constructed in an area that enforced building codes and the building code department interpreted the code correctly. Most building code inspectors just remember the part about retaining walls over 4 feet are required to be designed. They don’t see parts of a common house foundation as being a retaining wall. Step down foundation walls over 4 feet, the retaining walls typically associated with a walkout basement over 4 feet and any garage wall retaining material over 4 feet.
I would guess 99% of the homes built around my area never has a set of plans drawn by an architect. Most architectural plans drawn by small firms disclaim the foundation for two main reasons, they don’t have a structural engineer on staff and the soil property is site specific.