Homeowners often assume insulating an old brick house is a simple upgrade, but there's a hidden catch: furring out the walls for insulation adds real thickness that can compromise code-required stair and hallway widths.

To insulate against old brick, we typically frame 5 inches out from the brick face — accounting for an air gap, a 3.5-inch stud, and 0.5-inch drywall, plus a margin since old brick walls are rarely perfectly plumb. That 5 inches doesn't matter much where a staircase is already being replaced as part of a larger renovation. But on an existing staircase that isn't otherwise being touched, pushing the wall in by 5 inches can immediately take the landing or run below code minimums.

This is a genuinely common tension in whole-home renovations: fully insulating an old house can mean either isolating and skipping insulation right at the stairwell, or the homeowner choosing not to insulate a section of the house at all because rebuilding a code-compliant staircase (and the hallway changes that cascade from it upstairs) gets expensive fast. It's a good example of why a renovation plan has to be looked at holistically rather than wall by wall.