Older homes with open frame stucco can present unique challenges, especially when updating for earthquake retrofitting and insulation. Tony from Southern California asked for advice on how to brace the walls since there’s no sheathing.
Question from Tony:
Our house in Southern California was built in 1970 and has an open frame stucco job (no sheathing). I plan on removing all the interior sheetrock to earthquake retrofit, insulate, etc. Are there any techniques for bracing the walls in lieu of the lack of sheathing? Thinking of letting in diagonal bracing on the interior walls or lining all the walls with a nice grade plywood.
Disclaimer: Before diving into my recommendations, I want to note that I am not a structural engineer—I’m just offering my personal perspective based on your question. These are steps I might take if it were my house, but for a professional opinion and to ensure compliance with building codes, please consult with a licensed structural engineer.
Answer:
Hi Tony, It’s great that you’re taking proactive steps to retrofit and improve your home. In homes without exterior sheathing, adding structural bracing on the interior is an effective way to increase the wall strength and improve earthquake resistance.
Diagonal Bracing: Letting in diagonal bracing between the studs is a traditional and effective technique. This involves cutting slots into the studs and fitting diagonal 1x4 braces, which are then securely nailed or screwed in place. This method maintains the open wall cavity for insulation and is less invasive than full wall sheathing.
Plywood Sheathing on the Interior: Lining the interior walls with plywood is an excellent solution, especially if you’re removing the sheetrock anyway. A nice grade of 1/2" or 3/4" plywood can add significant strength and stiffness to the walls, improving their resistance to lateral forces during an earthquake. Once installed, the plywood can be covered with drywall for a finished look, maintaining a traditional interior look and feel still.
Combination Approach: Depending on your budget and wall configuration, you could use a combination of these techniques. For example, use diagonal bracing in less critical areas and plywood sheathing in key load-bearing sections of your home, like the exterior walls.
Additional Tips: Here are some other things I thought of for you to take into consideration too.
- When using diagonal bracing, ensure the braces are cut to fit tightly and fastened securely with screws or nails rated for shear strength. This will maximize their effectiveness.
- If you opt for plywood sheathing, use a continuous sheet where possible and follow proper nailing patterns for maximum rigidity. Blocking may be needed at seams to ensure a secure connection. You will also need to consider the electrical boxes and the added thickness of the plywood.
- Plan your bracing layout strategically to avoid interfering with electrical wiring or plumbing runs inside the walls.
These upgrades will significantly strengthen your walls, good luck with your project, Tony!
