what is a sill
Removing and Replacing a Rotten Sill Plate. A rotten sill plate is a common occurrence in old housesâand a big problem. The sill is the piece of wood closest to the ground, either on a foundation or piers, and is usually a âtimber-sizedâ board: 3Ã6, 3Ã8, 4Ã6, 4Ã8, and so on. The studs often rest directly on the sill and are toe-nailed in with no bottom plate as youâd find in a modern house.