Q. I'm planning to form a simple 4-foot stem wall foundation for a single-story garage using plywood, snap ties, and walers. It needs to have a brick ledge for the top 10 to 12 inches, which will show above grade. What's a simple, effective way to do this? Should I transition from a 10-inch wall, or can I use an 8-inch wall and reduce the thickness at the top? Would rigid foam board make a good

A.Jay Meunier responds: Sometimes Styrofoam is used for forming pockets in complicated areas because it's so easy to shape. But it's fairly costly and has to be handled very carefully when you remove it from the formwork if you plan to use it a second time. A simple, inexpensive way to form your brick shelf is with 2x4s and 1/2-inch plywood (see illustration, below). Make a short "wall" with a top and bottom plate and uprights every 18 to 24 inches and skin it with the plywood. It's easiest to build the shelf form separately, then nail it into place as the forms are set.

Unless you have design or loading requirements necessitating a 6-inch stem in your wall, an 8-inch wall will work fine to carry a 4-inch brick shelf. The 4-inch stem makes it a little more cumbersome to place concrete in the wall, especially if it contains a mat of rebar, so plan on the pour taking a little longer than usual. When placing the concrete, consolidate the concrete underneath your brick shelf by using a concrete vibrator or rapping your formwork with a mallet. This will give the shelf area a clean, square edge and setting surface.

Jay Meunier ran his own concrete contracting business for many years, and is now an estimator with Pizzagalli Construction in Burlington, Vt.