Foundation bolts for increased earthquake resistance
I've searched this forum for posts on Eichlers and earthquakes and they has been remarkably little discussion about this topic. I'm in the middle of a major interior remodel, and am having my contractor add some shear wall bracing to some interior walls. Another modification I am considering is adding more foundation bolts. My 1959 Eichler has bolts about every 3 ft. in the exterior walls only. There are no bolts in any interior wall. If the interior walls were also bolted, an earthquake would be less likely to cause door frames to go out of alignment, which is costly to correct.
Anyone on this forum ever had bolts added to their interior walls?
By the way, another earthquake safety-related modification I'm doing is replacing ALL the original glass with double-pane tempered glass, though my primary reason for doing this is to reduce exterior noise and insulate the house more effectively (although from a strictly economic point of view, I can never recoup that cost).
Thanks.
Non-professional reply: If I had my walls out, adding shear strength and doing the work you're doing, I would definately do it. It's like having a nice sturdy wall and as soon as the first tremor hits, your nice sturdy wall is sliding around. Plus you'll sleep better at night.
The only caveat is your radiant heat pipes. You could run your boiler and map your pipes with an infrared thermometer.
Oh, and don't forget to run your hot and cold water when you check for pipes.
Good luck!
I also added 1/2 inch extra foundation bolts just on the outside walls but none on the interior because you can damage the heater pipes. I also added brackets to all the post to prevent uplift and install strapes to the post and beam.
My architect has advised me that there is no reason to add foundation bolts to interior walls, since they are not over a footing, writing:
"The standard spacing for foundation bolts for new construction is 48" on center, with a minimum of 2 bolts per sill piece (piece being an uninterrupted section between doors or other breaks). The biggest change in recent years was to add 2" x 2" x 3/16" steel plate washers at each bolt, to prevent the bolt from tearing through the wood sill plate. If the walls are open and you want to increase the shear resistance, I'd add the washers to the existing bolts."
So I won't bother with bolting the interior walls.
By the way, if you want to add them to interior walls, the chances of hitting a radiant heat pipe are very slim. Eichler did not run pipes under walls (or even under kitchen counters), though it is possible that the radiant installer might have done so for reasons of expediency. So damaging one with a bolt in an interior wall is extremely unlikely.
That's good info to know. My kitchen was remodeled by the previous owner and the peninsula was taken out. There definately is a cold area on the floor where the peninsula cabinets used to be.
Hi Barry:
While the exterior walls should be bolted as your architect describes (and 5/8" bolts are the norm nowadays,) beyond that it's hard to generalize.
When I had my house open I had a structural engineer come look at it. For my floor plan, bolting wasn't so much of an issue. There were some weak points though, such as around the garage door, which is a very big opening with not much shear strength around it. We had a very narrow piece of wall next to the garage door that we added hold-downs to. He also recommended strapping where one wall terminated against another. These are case-by-case issues, though.
Also a big factor in what holds an Eichler together is the roof. If you ever have that exposed, it's worth looking at the nailing if you can. Think of it as a big plane that ties all your walls together.
Over engineered anything is a good thing, within limits/reason.
BUT, there is another potential issue and it's the heating tubes. You might drill into one or more of them.
