Why the connections matter most
The same Building America guidance says the main causes of deck failures are weak connections between the deck ledger (the board that attaches the deck to the house) and the house rim board, and deficient guardrail systems, with decayed wood and corroded fasteners often contributing. NADRA, the North American Deck and Railing Association, calls the ledger a common source of deck failure in its Check Your Deck consumer checklist. Many of these connections are hard to see from the yard, which is one reason a visual check by a homeowner can't confirm a deck is sound.
What to look for from a safe spot
Keep your own check visual. Stand on firm ground outside the deck's footprint in daylight and use your phone's zoom instead of a ladder or crawling underneath. Don't bounce on the deck, shake posts, pry at connections or remove coverings to get a better look. If you can't see an area safely, note it as not checked rather than assuming it's fine.
Things worth flagging, drawn from NADRA's consumer checklist and its professional deck evaluation checklist:
Wood: splits, decay, or small holes that may point to insects, especially in areas that stay damp, get regular water exposure, or sit against fasteners.
Hardware: loose, rusted or corroded fasteners, bent or modified joist hangers or post connectors, and red rust on connectors. NADRA's consumer checklist notes that a corroded fastener can cause deterioration in the surrounding wood.
Overall shape: deck boards or stairs that don't look even, visible sagging, or a deck that sways or moves in ordinary use. A NADRA article, Keeping Your Deck in Check, also lists sinking or heaving among the things to inspect.
Posts and footings: cracks, decay or corrosion on posts. NADRA's evaluation checklist points out that decay may show up just below where a post meets the ground, which is easy to miss from above.
These are reasons to call someone, not a diagnosis. NADRA's consumer checklist suggests probing wood with a tool to test for soft spots, but on structural members that's better left to the inspector, and if you've already noticed swaying, describe it rather than trying to make it happen again.
Arranging the inspection
NADRA's checklist says that checking a deck with its list doesn't make it code compliant, and it recommends having a professional such as a deck builder or home inspector do a deck evaluation. NADRA's professional checklist covers stairs, footings and posts, beams and joists, the ledger, the deck surface, and handrails and guards as separate parts, so ask for an evaluation of the structure and its connections, not just the deck boards. If only the surface is worn, our guide to replacing deck boards without rebuilding the frame explains when that's a separate question.
Share dated photos taken from a safe position and note when you first noticed each concern; our photo checklist for repair estimates covers what to capture. Ask the inspector to say what they couldn't reach or see, whether the deck should stay out of use, and whether a structural engineer should look at it. NADRA's professional checklist cites code editions such as the 2018 International Residential Code, so ask about current local requirements rather than relying on it for code questions.
Philadelphia and Bucks County
If the inspection leads to rebuilding or structural repair, ask the contractor whether the work needs a permit and which office issues it in your city, borough or township. For an older Northeast Philadelphia home, looking up the property's permit history can show what earlier deck work was permitted, and our contractor hiring checklist for Philadelphia and Bucks County lists questions to ask before you sign.