Building Codes Division is preparing to print the next edition of the residential code that is scheduled to become effective October 1st of this year. One of the changes is to foundation anchorage when using anchor bolts.
Wood sill plates at all exterior walls and sole plates on interior braced walls on a slab foundation are required to be anchored to the foundation with a minimum of ½ inch diameter anchor bolts spaced not more than 6 feet apart. No less than 2 bolts are required per plate section; and the bolts must be placed not more than 12 inches or less than 7 bolt diameters from the end. A wall less than 12 inches in length does not require an anchor bolt; and a wall less than 24” in length is allowed a single anchor bolt placed in the center.
The code will now contain an additional requirement for the anchor bolt to be placed in the middle third of the sill plate. This will require greater precision when bolts are installed during the pour.
There has not been a code requirement before for how close a bolt can be to the edge of the sill plate. Standard industry practice has been to keep them at least 2 bolt diameters from the edge. Anchor bolt manufacturers specify in their installation instructions to keep the bolts a minimum of 1-3/4” from the edge of the plate. Testing has shown an anchor bolt loses some of its capacity when placed closer than 1-3/4” from the edge.
To comply with the new rule an anchor bolt in a 2 x 4 plate can be no closer than 1-1/8” from the edge; and in a 2 x 6 plate can be no closer than 1-3/4”.
It would be wise to make sure your concrete sub is aware of the requirement before the rule takes effect.
Other methods of foundation anchorage are still permitted, such as foundation anchors, wedge anchors, expansion anchors, adhesive anchors, and other methods approved by the building official. These methods need to be installed in accordance with the manufacturer’s specifications.