Why Flashings Matter More Than People Realize

Anywhere a deck or porch attaches to a house, moisture has to be sealed against — and that matters even more where the structure meets masonry, since masonry actively transmits moisture rather than blocking it.

We inspected a porch that was clearly built more than 50 years ago — old enough that the brick ties were oversized by today’s standards, often a 3/4″ or full 1″ bolt. Structures like this typically fail for one of two compounding reasons.

The first is neglected flashing. Years of a slow, unnoticed leak can gradually rot a structural beam to the point where it can no longer support snow load, or even its own weight — long before anything looks visibly wrong from the outside.

The second is undersized footings. When footings are slightly too small for the load they carry, seasonal freeze-thaw cycles and wet soil in fall or spring push them deeper into the ground over time. That gradual settling levers the whole structure away from its original connection to the house.

Neither failure mode announces itself early. That’s exactly why proper flashing at the house connection, and footings sized for the actual load rather than the minimum, are two details worth never cutting corners on.