Below is an image of what it looks like under a house without a cripple wall.    The red arrows represent earthquake forces trying to slide the floor off the foundation.  The joists that sit on top of the mudsill are called end joists on one side of the house and rim joists on the other side

Earthquake Forces on Joists

The way this sliding is corrected is by attaching the end joists and rim joists to the mudsill with Shear Transfer Ties, sometimes known as framing anchors.  A large variety of shear transfer ties are available and a contractor must know which one to use when confronted with every imaginable framing configuration.  Given that many houses were built without a building code, the varieties of floor framing are legion.

Below are the names of some of the Shear Transfer Ties available.  These are also known as framing anchors.

L70, L90, LS70, LS90, A23, A35,

LTP4, H10R, H10, H2.5, lag bolts,

12d toenails, 8d toenails, 15 gage staples

Often they must be fabricated out of wood on site.

Shear Transfer Tie Restrained by STT

Each Shear Transfer Tie can resist a certain amount of force.

Below is a photograph of a single L90 Shear Transfer Tie.  It is nailed at the back to the floor framing and at the bottom to the mudsill.   (The bottom nailing to the mudsill  is not visible in this photo.)  The Shear Transfer Ties transfer earthquake force into the mudsill.

Single L90 with Arrow

 

 

In this illustration, the plywood (also called a diaphragm or Shear Transfer Diaphragm)  is nailed to the top of the new mudsill on one side, and to the floor joist where you see the red arrow on the other.  When the floor joist moves, that movement is transferred into the Side Bolt Mudsill and into the bolts, thereby preventing movement of the floor and saving the house.

Screenshot at Aug 30 17-43-29

 

When the floor joists run perpendicular to the foundation, a connection from the floor to the mudsill is made with Shear Transfer Ties.   When the Floor Joist moves in the direction of the red arrow, it pushes against the Shear Transfer Tie, which pushes against the mudsill bolted to the side of the foundation and is stopped by the bolts.

Screenshot at Aug 30 17-44-13

  • The image below shows how Shear Transfer Ties are part of a system.  The yellow arrow represents earthquake forces pushing against the floor you walk on.
  • The white arrow is force going into the Shear Transfer Tie which tries to make the mudsill slide.
  • Finally the red arrow shows that force  entering into the Foundation Anchor and into the Foundation.
  • Again, this is only one kind of Shear Transfer Tie.  There are many others.

Screenshot at Sep 08 19-17-34

Below you can see how Shear Transfer Ties are used when new mudsills are placed on the side of the foundation.

 

 

 

 



SHEAR TRANSFER TIE WITH STAPLES

SHEAR TRANSFER TIE WITH STAPLES

The houses below were bolted, but the floor was not attached to the mudsill with nails or Shear Transfer Ties.

This is the first house

Blue House With Arrows

This is the third house

 

Types of Metal Shear Transfer Ties

This is the shear transfer ties

Some Shear Transfer Tie types by Simpson Strong-Tie