Seismic Retrofit Evaluation in Northeast Portland
Retrofitting a large Northeast foursquare is a different proposition from retrofitting a bungalow, and the difference is mass. These are two and a half storey houses with heavy framing, sometimes masonry chimneys running the full height, and a great deal more weight for the connection at the foundation to hold.
More weight means more anchors, closer spacing, and hold-downs at locations a small house would not need them. It also means the foundation is doing more work, so its condition matters more than it does under a light bungalow — the same friable concrete that is a problem under a small house is a larger problem under a big one.
These houses also frequently have partial basements rather than crawl spaces, which changes the geometry entirely. Where a basement wall is full height there is no cripple wall to brace, and the retrofit becomes about anchorage and about the connection between the floor diaphragm and the top of that wall — a different set of details from the standard bungalow package.
What We Look At Here
- Building weight and resulting anchor spacing and hold-down requirements
- Foundation condition assessed against the higher loads a large house imposes
- Whether the perimeter is cripple wall, full-height basement wall, or a mixture
- Diaphragm connection at the top of full-height walls where no cripple wall exists
- Unreinforced masonry chimneys, which are a separate hazard from the frame
- Continuity of the load path around additions and previously altered sections
More on the service itself: Seismic Retrofit Evaluation. More on the area: Northeast Portland.
Questions
Frequently Asked Questions
Is retrofitting a large Laurelhurst foursquare different from a bungalow?
Yes — more weight means more anchors and hold-downs, and these houses often have full-height basement walls rather than cripple walls, which changes the details entirely. The standard bungalow retrofit package frequently does not apply.