Most deck repair conversations start with the boards, because boards are what you look at. Boards are also the least important part of a deck. The parts that hold people off the ground are underneath and behind, and those are the parts worth your attention first.
Inspect from the structure outward
Work in this order, because it reflects consequence rather than visibility.
The ledger. This is the board attached to the house that carries one edge of the deck. It is where most catastrophic deck failures begin. Look for: fasteners that are nails rather than approved structural fasteners, rust, any gap opening between the ledger and the house, water staining on the siding above it, and missing flashing. If the ledger was attached with nails or the flashing is absent, that is a serious finding regardless of how solid everything feels.
Posts and footings. Posts should bear on footings, be secured with proper connectors, and show no rot at the base. Posts set directly in soil are a common older practice and a common failure point. Push hard on the structure and watch for movement.
Beams and joists. Probe with an awl or a screwdriver anywhere water collects: joist tops under the decking, the ends of joists at the ledger and beam, and anywhere two pieces meet. If the tool sinks into the wood, that is rot, and rot spreads along the grain further than it looks.
Connectors. Joist hangers, post caps, and hold-downs should be present, fully nailed with the correct fasteners, and appropriate for treated lumber. Standard fasteners corrode quickly in contact with modern treated wood; the connectors and fasteners need to be rated for it. Rusted connectors and empty nail holes are both problems.
Guards and stairs. Railing posts should not move. Guard height, baluster spacing, stair rise consistency, and handrail graspability are all code items and all involve real fall risk. Stairs with a loose or missing handrail and a wobbly guard are among the most common injury sources on a deck.
Then the boards. Splits, cupping, splintering, and surface rot.
What is reasonably repairable
- Individual damaged deck boards
- Popped or corroded deck screws and nails
- Loose railing sections where the framing behind them is sound
- Surface finish, cleaning, and resealing
- A single joist with localized rot, sistered or replaced with proper connections
- Adding a proper flashing detail where accessible
What is not a board-level fix
- A ledger attached improperly, or any evidence of ledger movement
- Widespread framing rot
- Posts rotted at grade or set in soil
- Missing or wrong structural connectors throughout
- Guards that fail a firm push test
- Any deck that sways under normal walking
These involve load paths, and the correct response is an assessment by a qualified contractor or engineer plus a permitted repair, not enthusiasm and a box of screws.
When replacement beats repair
Add up the findings. If the framing is largely sound and the problems are boards, fasteners, and finish, repair is clearly the better value. If the ledger detail is wrong, the posts are compromised, and the framing has multiple soft spots, you are rebuilding the deck one piece at a time at a higher total cost with a worse result.
Age matters here, because construction requirements for decks have changed considerably. A deck built decades ago may have been built to what was accepted then and still be well short of current expectations for ledger attachment, lateral load connections, and guard strength.
Doing board replacement well
If the structure checks out and you are replacing boards:
- Match the thickness and width of the existing material.
- Use fasteners rated for treated lumber and for exterior exposure.
- Predrill near board ends to prevent splitting.
- Leave the spacing the material calls for so water drains and the boards can move.
- Look at the joist tops while boards are off. This is your one easy chance to see them, and adding joist tape over the top of each joist keeps water from sitting in the fastener holes.
- Replace any fastener that is corroded rather than reusing.
Permits and inspection
Structural deck work generally requires a permit and inspection, and that is a feature rather than a hassle. Ledger connections and lateral load anchorage are exactly the details an inspector will look at, and they are the details that fail. Check with your local building department before starting structural work.
A deck is one of the few structures in a home where a hidden failure drops people from height all at once. It is worth the inspection.