I need to attach a sill plate to a foundation that does not have anchor bolts. I'd like to use GRK Caliburn screws. The sill plate is 1.5 inches thick. How long should the screws be?
It looks like 2-3/4" is a commonly sold length. Is that sufficient?
Best Answer
Anchor bolts are used to: 1) keep your house from sliding along the concrete foundation, 2) resisting the house from being peeled away from the foundation (like a zipper), or 3) keeping the house tight to the foundation so the house doesn’t float away.
Your house has shear walls that need to be fastened to the foundation. I live in a high wind area so our requirement is 5/8” bolts at 24” on center. Depending on your wind loads, you’ll need sufficient anchor bolts of sufficient diameter to resist winds in your area.
Shear walls keep the house square and upright, but the shear “box” could be tipped over if the corners are not anchored down. In fact, where I live 3” square washers are required to keep the plate from pulling through the head of the anchor bolt. If you live in a seismically active area like Santa Barbara, CA then theses anchors are designed to keep your house anchored to the foundation (and your foundation is designed to resist such seismic forces.)
In high flood areas the wood house could float away without sufficient anchors.
All of these loads (stresses) need to be calculated or you need to use the standard Building Code requirements.
I doubt your “screws” would satisfy any of these stresses. I’d use anchor bolts.