In Part 1 of this series about the conversion of my detached garage into an accessory dwelling unit (ADU), I discussed the structural issues related to the roof of the garage. In this Part 2, I will discuss structural issues relating to the walls of the garage and how I dealt with them.
My existing garage has conventional wood framing walls with 2X wood studs spaced at 24″ on center. These studs are exposed on the inside (i.e. not covered with drywall) and are attached to the exterior siding panels. Since a good part of the siding panels is rotted, I decided to replace the whole thing with plywood siding panels T1-11. In addition, because this garage was built in the 1940s, the wall framings were not anchored to the foundation. In fact, part of the South wall was already sliding off the foundation! Since I’m living in earthquake country here in California, I decided to add Simpson hold-downs for all four exterior walls as well as the new interior wall to turn these load bearing walls into seismic resisting shearwalls.
New Seismic Hold-down at Shearwall Corner
Besides the lack of seismic hold-downs and some rotting of the exterior siding panels, the walls were in fairly decent condition so I wanted to keep them in tack as much as possible to keep the cost of the project down. However, there were some issues with these existing walls that made this very difficult to achieve. I’m going to talk about each of the four exterior walls individually below.
South Wall
As an existing garage, this wall had a window right in the middle of it. It also faced the big part of my yard so I wanted the new ADU to have as many openings on this wall as possible to let natural lighting into the ADU. To make this happen, I added a patio door and a big window for the kitchen on this wall. These opening essentially wiped out the whole existing wall, so I gave the Contractor permission to reframe the whole wall.
South Wall Before and After
North Wall
The north wall had the door for entrance into the garage. For the new ADU, I did not want to have any openings for this wall since it faces the main house. This is because if I decide to rent the ADU out, I want to give both the tenant and myself as much privacy as possible. The best way to do this is to not have our windows face each other. For this wall, since not much work needs to be done, we were able to keep the existing wall and just frame up the existing door.
North Wall Before and After
East Wall
This wall was made up almost entirely by the existing garage door, so it essentially needed to be a brand new wall for the ADU. The new wall framing for the ADU has a new entry door and a large window for the bedroom.
East Wall Before and After
West Wall
The current wall had no opening and the new wall is only scheduled to have a small opening for the bathroom window. I really wanted to save this whole wall to save some money for the project. However, this wall was the wall that has the most problems. Since there were no seismic hold-downs or attachment of the wall to the concrete foundation below, part of the wall has already slid off the foundation. The wall was not reusable so I ended up having the Contractor build a brand new wall. We did this by shoring this part of the roof, take the existing wall out, and building a new wall in its place.
Reconstruction of the West Wall
In Part 3, I will discuss the extensive structural modifications to the foundation of the ADU.
If you are looking to get in touch with a Contractor to help you with your ADU project, reach out to me at [email protected] and I can give you recommendations for some excellent Contractors.Disclaimer: The structural issues identified in this post are specific to my ADU and may or may not apply to your specific situation. Please use your own engineering judgment or consult with a civil/structural engineer for your specific situation.