We're doing a renovation job on a residential basement. As part of the work, we're removing backfill in one area and cutting a 3-foot-wide door in the concrete foundation wall to create a walkout basement. Then we're adding a timber retaining wall to hold back the backfill on each side of the door. Because we've removed the earth, soil beneath the part of the footing at the door is exposed to freezing. Should we protect the footing by putting insulation beneath the concrete sidewalk leading away from the door?
We asked Kansas City, MO, consulting engineer Willard Norton to answer your question. He says that insulation isn't needed. Only a small length of the footing is exposed, and there will probably be enough heat loss from the basement at the doorway to prevent ground freezing.