If you ’re building a new home, don ’t forget to use a foam sill sealer that sits on top of the foundation and under the treated wood sill plate. (Tim Carter) ...

These kits typically yield 200 board feets’ worth of spray foam, making them a good candidate for medium-sized projects, like sealing roof and wall junctions, attic walls and basement sill plates.

Snap Lines on the Floor Snap a line on the floor 4-in. away from the foam as a guide for the bottom plate. This will leave a 1/2-in. gap between the bottom of the new wall and the foam.