retrofitting homes slides

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

The End

Eddie SandovalTel: 415-680-2112

esandoval@cal-insure.com