How to Repair a Deck: Fix Boards, Railings, Ledger, and Structure (2026)

Frequently Asked Questions

How do I know if a deck board needs to be replaced?

Poke each board with a screwdriver or an awl, especially at the ends and at every joist crossing point. Sound wood resists the poke. Soft spots where the tool sinks in more than 1/4 inch indicate rot. Also look for checks (cracks running along the grain), heavy splinting, large splits that catch feet, and boards cupped over 1/2 inch that cause trip hazards. Surface weathering is cosmetic and doesn't require replacement — rot and structural failure does.

Can I replace just one or two deck boards?

Yes. Deck board replacement is the most common DIY deck repair. You don't need to remove the whole deck — just cut out the rotted section (or pull the full board if it runs the whole width), snap a chalk line if needed, and install a new pressure-treated board. Match the lumber species and width to your existing boards. If your deck has 5/4 decking (1 inch thick), buy 5/4x6 — not 2x6.

What kind of wood should I use to replace deck boards?

Match your existing deck material as closely as possible. Most decks use: pressure-treated pine (most common, cheap, must weather before staining), cedar (naturally rot-resistant, lighter), redwood (premium, naturally rot-resistant), or composite (Trex, Fiberon — cannot be nailed, uses hidden clips). For a full deck replace, composite costs more upfront ($3–$12/linear foot vs. $1.50–$4 for PT pine) but never rots and needs no sealing.

How do I fix a wobbly deck railing?

Loose railings are usually one of three things: (1) The post base has rotted at the deck surface — replace with a new adjustable post base bolted to the joist. (2) The post base bolts have loosened or the wood around them has split — add a through-bolt with a washer plate, or sister a new 4x4 alongside the old post. (3) The top and bottom rails are loose at the post — add metal rail connectors or through-bolts at each connection. All railing work should result in zero movement under 200 lbs of lateral load — that's the standard.

My deck is pulling away from the house — what's wrong?

This is a ledger failure — the ledger board is the horizontal member bolted to the house that supports one end of the deck joists. Causes: improper flashing that let water behind the ledger causing rot, undersized lag bolts, or lag bolts into rim joist that lacks backing. This is a structural failure and falls. Have a contractor or structural engineer inspect before using the deck. In some cases, the ledger and all lag bolts can be replaced without rebuilding the whole deck.

Deck repairs range from a 30-minute single-board swap to a multi-day structural overhaul. Here’s how to diagnose what you have and fix it correctly.

Start with a deck inspection

Do this every spring before deck season, and any time you hear creaking, see movement, or notice soft spots.

Walk the deck:

• Does it flex or bounce underfoot? More than slight give suggests joist issues.
• Any lateral sway? Sway points to bracing failure or post problems.
• Check every railing — grab and push hard. Zero movement is the standard.

Probe for rot: Use an awl, ice pick, or stiff screwdriver. Poke every deck board at:

• The ends (where cuts were made — end grain absorbs water fastest)
• At every joist crossing (where water pools between board and joist)
• Any area with discoloration, dark staining, or soft texture

Poke the structure too:

• The tops of deck posts where they enter post bases
• The ledger board and all rim joists
• The underside of joists, especially at connections

Signs you need a contractor:

• Posts that flex at the base
• Joists that deflect visibly when you stand on them
• Ledger pulling from the house (even a 1/8 inch gap at the ledger flashing is serious)
• Multiple joists with soft spots
• Any signs the deck footings are heaving (concrete piers tilted or cracked)

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Repair 1: Replace rotted deck boards

Tools and materials:

• Pry bar / deck board removal tool — $15–$30
• Circular saw
• Drill/driver with composite/deck screws — stainless or hot-dipped galvanized only (zinc-coated regular screws corrode fast in PT lumber)
• Replacement lumber (pressure-treated 5/4x6 is most common)

Steps:

1. Remove the rotted board. Pry up the ends and middle — use a flat bar under the board and lever against the joist. For boards held by old nails, a cat’s paw nail puller pulls nails cleanly without splintering adjacent boards.

2. Inspect the joists underneath. If a joist is soft at the spot where the rotted board was, it likely has rot too. See Repair 4 below.

3. Cut the new board to length. Allow 1/8-inch gaps between boards for drainage (use a nail as a spacer). Deck boards expand and contract — don’t butt them tight.

4. Fasten with 3-inch deck screws, two per joist crossing. Pre-drill near the ends to prevent splitting. Countersink slightly so the screw head doesn’t catch.

5. If the board is warped, screw one end, clamp or step on the middle to pull it flat, then screw while holding flat. A board straightening tool helps with severely cupped boards.

Cost: $2–$5 per linear foot in PT pine. A standard 16-foot deck board replacement costs $10–$30 in materials.

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Repair 2: Fix loose or squeaky deck boards

If boards are loose but not rotted:

• Old nail fasteners — pull the nail, relocate slightly, and drive a deck screw instead.
• Board cup/twist causing squeaks — drive deck screws through the center of the board into the joist. Pre-drill to prevent splitting.
• Board movement at a gap — add blocking (a short piece of 2×8 or joist material) between joists under the problem area and screw the board into the new blocking.

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Repair 3: Fix wobbly railing posts

Railing failure is a safety hazard. Never defer this repair.

Surface-mounted posts (most common):

Posts mounted on top of the deck with post bases need two types of reinforcement:

1. At the base: Replace deteriorated lag bolts with new ones, or add a post base connector (Simpson Strong-Tie ABU44 or similar) and through-bolt through the decking and into the rim joist or blocking.
2. At the rail connections: Metal rail-to-post connectors add rigidity at top and bottom rail joints.

Rim-mounted posts (through the deck frame):

Posts that pass through the decking and bolt to the rim joist are stronger but can rot at the point where the post passes the deck surface. If rot is present:

• Sister a new 4×4 post alongside the old one, running from the rim joist to railing height.
• Cap the old post; the new post takes the load.
• Through-bolt both posts to the rim joist with 1/2-inch galvanized bolts.

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Repair 4: Sistering a damaged joist

If a joist has surface rot but the center wood is still sound:

1. Cut out any soft sections with a jab saw.
2. Treat the remaining wood with wood hardener and let cure.
3. Cut a “sister joist” — the same dimensional lumber (2×8, 2×10) at the same length.
4. Apply construction adhesive to the face of the damaged joist, clamp the sister joist against it, and through-bolt with 1/2-inch galvanized bolts every 16 inches.

If the joist is fully rotted through, the sister joist can take the full load — but if multiple adjacent joists are compromised, call a contractor.

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Repair 5: Re-secure the ledger

A deck ledger that is pulling away from the house must be addressed before anyone uses the deck.

Temporary: Brace the ledger from below with a temporary post and beam while you assess.

Permanent repair:

1. Remove deck boards over the affected area for access.
2. Inspect the ledger for rot. If the ledger wood is soft, the ledger must be replaced — which is a significant undertaking (all joists must be temporarily supported, old ledger removed, new ledger installed with proper flashing).
3. If the ledger wood is sound but fasteners have backed out: drill new holes and install additional 1/2-inch lag bolts or structural screws (LedgerLOK) in a staggered pattern — one every 16 inches. Bolts must go into the band/rim joist of the house, not just sheathing.
4. Re-flash with Z-flashing to direct water away from the ledger-to-house junction.

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Repair 6: Replace a cracked or rotted post

Deck posts (the vertical supports holding up the frame) are structural. Rot at the base of a post is a collapse risk.

1. Jack up the deck beam at that post location with a temporary post and hydraulic jack — just enough to take the load off the post.
2. Remove the old post base hardware and pull the post.
3. Set the new post into the adjustable post base — the base holds the post 1 inch above the concrete footing to prevent moisture transfer.
4. Shim plumb, lower the jack slowly to transfer load to the new post, and fasten the post cap and base hardware.

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Staining and sealing after repairs

New pressure-treated lumber must dry for 6–12 months before staining or sealing. New cedar and redwood can be stained immediately with a penetrating oil stain.

See How to Stain a Deck for the full prep and application process.

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Related guides

• How to Stain a Deck — prep, stain selection, application
• Deck Building Cost Per Square Foot — full replacement cost if repairs aren’t worth it
• How to Power Wash Your House — clean the deck before staining or inspection
• Annual Home Maintenance Schedule — when to do your annual deck inspection
• Handyman Cost Guide — what structural deck work costs to hire out