retrofitting homes slides
TRANSCRIPT
Seismic` Retrofitting
The 3 Main Components of a Retrofit
1. Bolt cripple walls to foundation
2. Secure cripple walls to the floor joists
3. Install plywood shear panels
Step 1: Bolting to Foundation
• Bolting is only of value where walls have been braced with plywood
• The number of bolts is calculated to have the same resistance capacity as the plywood
Installed Anchoring
Bearing Plates (Plate Washers)
Bearing plates increase strength of bolt-to-wood
connection SEAOSC Research
Problems With Existing Bolts
• Oversized bolt holes are found in most existing bolt installations.
• More than 1/16 of an inch larger than diameter of bolt is considered oversized.
Mudsill Splitting
• Caused by over-sized holes
• Over-sized holes are common because they allow builders to adjust the position of the mudsill
Foundations Anchors for Crawlspaces
Foundation plates replace bolts where drill-space is unavailable
Step 2: Secure Cripple Wall to Floor
Movement prevented by shear transfer ties
Shear Transfer Ties Installed
There are three ways to attach a plywood panel to the mudsill:
• Directly to Flush Framing
• The Nailed Blocking Method
• The Flush Cut Method
Step 3: Install Plywood Shear Panels
1. Directly to Flush Framing
2. Nailed Blocking Method
2x4 blocks installed between 2x4 studs on 2x6 mudsill
3. Flush Cut Method
Nailed Blocking > Wood Splitting
• Improper nailing often causes wood splitting
• Pneumatically driven staples can be driven closer and reduce splitting at time of driving and when loaded in shear
Plywood Installation Challenge #1
Updated plumbing, wiring and structural modifications
Plywood Installation Challenge #2
Old-fashioned, inconsistent and odd framing
Plywood Installation Challenge #3
Replacing rotted or pest-damaged wood
How Not to Nail Shear Panels
The Finished Look: Cripple Walls
Shear walls with finished-to-match panels between
The Finished Look: Crawlspace
Anchor plates and shear transfer ties house to foundation
