Our house was built in 1956. We live close to San Andreas fault line, it is within 10 miles distance to the house, in San Francisco Bay Area.
The house has no cripple walls and it is a single story, ranch style house. It has a crawlspace, and a foundation wall of about 2 ft high. The floor system directly sits on the foundation wall. There is a 4x6 lumber on top of the 2x6 mudsill and the floor is nailed to 4x6 on the perimeter. Floor joists are also 4x6, spaced every 4 ft OC. Sill plate is bolted to foundation every 6 ft.
Due to a small renovation, I removed the plaster walls from some exterior walls. Now that the walls are open, I wonder what can be done for seismic retrofitting those walls. I will add foundation plates and framing angles below the flooring where it is needed. I will also add a plywood under drywall and use shear wall nailing pattern to increase lateral strength. But I don't see a good way to add a steel holdown in the open walls. It is too far from foundation and I need to drill through 10" of wood to get to foundation.
So, my questions are:
- Is a holdown needed in this case?
- Can a holdown be attached to the 4x6 lumber using 1/2" structural screws?
- What else can be done to strengthen the walls?
Reference: http://www.strongtie.com/ftp/fliers/F-SEISRETRGD12R.pdf
The house has no cripple walls and it is a single story, ranch style house. It has a crawlspace, and a foundation wall of about 2 ft high. The floor system directly sits on the foundation wall. There is a 4x6 lumber on top of the 2x6 mudsill and the floor is nailed to 4x6 on the perimeter. Floor joists are also 4x6, spaced every 4 ft OC. Sill plate is bolted to foundation every 6 ft.
Due to a small renovation, I removed the plaster walls from some exterior walls. Now that the walls are open, I wonder what can be done for seismic retrofitting those walls. I will add foundation plates and framing angles below the flooring where it is needed. I will also add a plywood under drywall and use shear wall nailing pattern to increase lateral strength. But I don't see a good way to add a steel holdown in the open walls. It is too far from foundation and I need to drill through 10" of wood to get to foundation.
So, my questions are:
- Is a holdown needed in this case?
- Can a holdown be attached to the 4x6 lumber using 1/2" structural screws?
- What else can be done to strengthen the walls?
Reference: http://www.strongtie.com/ftp/fliers/F-SEISRETRGD12R.pdf