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Lag Bolts

Cripple Wall Floor Connectors using Lag Bolts

In retrofit shear walls it is always necessary to use Cripple Wall Floor Connectors to attach the shear wall braced cripple wall to the floor it is supposed to restrain.   When the wall is covered with plaster or sheet rock, cripple wall floor connectors can either be installed by removing the sheet rock in the ceiling to access the floor framing, or preferably by using lag bolts, which function as Shear Transfer Ties.   Rather than removing the sheet rock, a more cost-effective approach is to use lag bolts to connect the top of the shear wall to the floor above.  How this difficult concept works is shown in the illustrations and photographs below.

We also often find shear walls in existing retrofits covered in sheet rock and there is no visible sign shear transfer ties were were installed.  In these cases, we must remove a strip of plaster 12 to 18 inches wide so that we can access the floor and connect it to the top of the shear wall.  The brown part of the photo below is where the plaster has been removed. When done we replace the plaster with sheet rock but do not texture or paint it.

When there is sheet rock  on the ceiling there are two ways to connect the floor to the shear wall.  In these cases we remove a strip of plasteror sheet rock 12-18 inches wide so the we can access the floor and connect it to the top of the shear wall.  The dark brown part of the photo below is where the plaster has been removed.  This is where we put metal floor to braced shear wall connectors called shear transfer ties.


At other times we are able to drive lag bolts up through the top of the shear wall into the floor joists.  These bolts attach the floor to the shear wall and secure it from sliding.

Lag bolt cripple wall to floor connector being installed


Here you are looking at someone driving a lag bolt up through the top plate and into the floor framing.  This joins the top plate to the floor joist that will be trying to move.  When the floor moves, that movement is transfered to the upper top plate, which the plywood is nailed to.  These do the same thing as shear transfer ties.  This is very handy when sheet rock is on the ceiling because one does not need to remove any of the sheet rock on the ceiling to access the floor framing.  One can attach it to the top of the cripple wall.  In the illustration below, the shear transfer tie number “2” connects the top of the cripple wall to the floor.  Lag bolts do the same thing when driven through the top plate at location “3” into the floor.  This connects the floor to the top of the cripple wall.




In the illustration below, “Load” means earthquake force.

Cripple wall floor connector lag bolt side view

The drawing below shows how a lag bolt can do the same thing as a shear transfer tie without removing the plaster.  Here you are looking at it from the end.

Lag Bolt Cripple Wall Floor Connector Front View

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