What sill plate means
The sill plate is the board laid flat on top of the foundation wall, bolted down, that the floor framing or wall sits on.
Also called mudsill, sole plate.
Where it matters on a carpentry job
It is the framing member closest to the ground, so it rots and gets termite damage first. Pressure treated lumber and anchor bolts are standard; replacing a rotten sill is a jacking job and priced as one.
What the model code says
- Sill plates are anchored with at least 1/2-inch anchor bolts spaced not more than 6 feet on center, or approved equal anchors. (IRC 2021, Chapter 4)
Check which code edition your building department enforces for sill plate before you quote.
Work it out
- Free calculator: Framing calculator
- Tools, templates and guides: Free carpentry resources
Sources: 2021 International Residential Code, Chapter 4, Foundations (ICC). Checked October 9, 2026.