According to code, what is the minimum bolt size used to attach foundation plates or sills to the foundation?

According to code, what is the minimum bolt size used to attach foundation plates or sills to the foundation?

• A. 3/8 inch
• B. 1/4 inch
• C. 1/2 inch
• D. 5/8 inch

Answer: (C)

The basic idea is that the connection between the foundation and the wood framing must be strong enough to resist uplift and other loads, so the code sets a minimum diameter for the anchor bolts used to secure the sill plate to the foundation. The smallest size that meets that requirement is 1/2 inch in diameter. Smaller bolts, like 1/4 inch or 3/8 inch, don’t provide enough strength under typical residential loads, while a bolt size of 5/8 inch would also work but is larger than the minimum. In practice, these 1/2-inch bolts are embedded in the concrete and fastened with nuts and washers to hold the sill plate firmly in place.

The basic idea is that the connection between the foundation and the wood framing must be strong enough to resist uplift and other loads, so the code sets a minimum diameter for the anchor bolts used to secure the sill plate to the foundation. The smallest size that meets that requirement is 1/2 inch in diameter. Smaller bolts, like 1/4 inch or 3/8 inch, don’t provide enough strength under typical residential loads, while a bolt size of 5/8 inch would also work but is larger than the minimum. In practice, these 1/2-inch bolts are embedded in the concrete and fastened with nuts and washers to hold the sill plate firmly in place.