A wood deck takes a beating from sun, rain, snow, and foot traffic every single year. Most decks do not fail all at once — they deteriorate board by board, and catching problems early saves thousands compared to a full rebuild. Here is how to assess your deck and repair the most common issues.

Deck Repair Guide

Inspecting Your Deck

Walk every square foot of the deck and push firmly with your foot on each board, especially near edges and around fastener holes. Soft, spongy spots mean rot has set in.

Check these critical areas:

Ledger board: Where the deck attaches to the house. This is the most critical structural connection. Look for gaps, rust stains, or soft wood. A failing ledger board is a safety emergency.
Posts and footings: Push laterally on each post. Any wobble means the connection to the footing or the beam is failing.
Joists: Look underneath the deck. Probe the bottom edges of joists with a flat-head screwdriver. Sound wood resists the blade; rotting wood crumbles.
Railings: Grab each railing section and shake it. Building codes require railings to resist a 200-pound lateral force. Wobbly railings are a fall hazard.
Stairs: Check stringers (the angled boards that support steps) for cracks, rot, and separation from the deck frame.

Replacing Deck Boards

This is the most common deck repair. Individual boards rot, crack, or warp while the structure underneath remains sound.

Remove the old board. Back out the screws with a drill/driver. If the board was nailed, pry it up with a flat bar and a block of wood to protect adjacent boards. A reciprocating saw can cut nails flush between the board and the joist if they will not pull.

Inspect the joist. Once the board is off, look at the joist surface. If it has surface rot but the core is solid, clean off the soft wood and apply a deck joist tape — a self-adhesive waterproof membrane that prevents further moisture damage.

Cut the replacement board. Match the species and thickness of the existing decking. Pressure-treated lumber is the most common. Let new pressure-treated boards acclimate outdoors for a week or two before installation to reduce warping.

Install. Set the new board in place with a 1/8-inch gap on each side for drainage and expansion. Drive two screws into each joist. Pre-drill near the ends of the board to prevent splitting.

Fixing Wobbly Railings

Loose railings are usually caused by failing post connections. Most deck railing posts are either bolted through the rim joist or notched over the rim joist and lagged.

For bolt-through posts, tighten the carriage bolts. If the bolt spins freely, the wood around the hole has rotted and the bolt has lost its grip. The fix is to add a post-to-rim-joist connector bracket — a metal bracket that bolts to the outside of the rim joist and grips the post on two sides.

For surface-mounted posts, check the lag screws. If the screw holes are stripped, drill them out and install larger-diameter lags, or fill the holes with epoxy and two-part wood hardener, let it cure, and re-drill.

Replace any post that is visibly rotted at the base. The cost of a single 4x4 post is trivial compared to the liability of a railing failure.

Structural Joist Repair

If a joist has rot concentrated on one end or one face but is otherwise sound, you can sister a new joist alongside it rather than replacing the whole thing.

Cut a pressure-treated 2x board the same dimension as the existing joist. Hold it against the damaged joist, flush at the top, and bolt the two together with 1/2-inch carriage bolts every 16 inches. The new board carries the load while the old one remains in place.

If the rot is extensive — more than 25 percent of the joist cross-section — replace the entire joist. Support the deck boards temporarily with jacks, remove the old joist, and install a new one using the same hanger hardware.

Fixing Popped Nails and Screws

Deck fasteners work loose over time as wood expands and contracts through wet and dry cycles. Popped nail heads are trip hazards and entry points for moisture.

For nails: pull the old nail with a cat’s paw, fill the hole with exterior wood filler, and replace with a 3-inch deck screw offset from the original hole by half an inch.

For screws: back them out, squeeze exterior wood glue into the hole, and drive a slightly longer screw into the same hole. The glue fills the stripped threads.

Stain and Seal Maintenance

Even if the structure is sound, an unfinished deck surface deteriorates faster. A good exterior stain and sealant blocks UV damage and repels water.

Clean the deck first with a deck cleaner and a stiff brush, or rent a pressure washer set below 1,500 PSI for softwoods. Let the deck dry for 48 hours. Apply one or two coats of exterior deck stain with a roller or sprayer, back-brushing to work the stain into the grain.

Plan to re-stain every two to three years. A well-maintained deck lasts 20 to 25 years before the structure needs major work.

When to Call a Professional

Most board and railing repairs are solid DIY territory. However, hire a licensed professional for:

Ledger board replacement or reinforcement (structural connection to the house)
Footing or foundation repairs
Rebuilding stairs that serve as the primary exit from an elevated deck
Any repair where you suspect the deck may not meet current building codes

A failing deck is not just an inconvenience — it is a life-safety issue. When in doubt, get a structural assessment before you invest in cosmetic repairs.