- Q.What is the best way
to insulate the footing, foundation, and slab on the walk-out
side of a basement?
A.Probably the easiest way is
to pour the footing and insulate the inside of the stem wall
with 2-inch-thick extruded polystyrene foam (see illustration).
The insulation should extend at least 2 feet below grade, and
the top can be tapered to a thin edge so it is concealed by the
interior trim. This works particularly well if there are
heating ducts in the slab near the perimeter.
An alternative is to insulate the slab perimeter, extending
the insulation at least 2 feet from the edge. Again, where the
insulation turns up along the perimeter, it should be tapered
so it can be concealed.
A third option, of course, is to insulate the outside of the
foundation with extruded polystyrene. The portion above grade
should be protected with stucco or foundation-grade
pressure-treated plywood. However, this system should not be
used if the walls have a masonry veneer.