Fix a wobbly deck railing

How a deck railing is held up

Most deck railings hang on their posts, and the posts are fastened to the outside of the deck's rim joist or end joists. Everything a person leans on transfers through those few fasteners at the bottom of each post. Nails and lag screws loosen as wood shrinks, swells and gets pushed on season after season, and a post that's notched to fit the deck leaves less wood to hold.

Building codes commonly require deck guards to resist a 200-pound push at the top, which takes solid wood, through-bolts and often blocking or metal hardware behind the rim joist. The fixes here firm up a railing that has loosened. If the posts or the deck framing are rotted, the repair is a rebuild, not a tightening.

Why deck railings get wobbly

Let's fix it

1. Find which posts movePush firmly on the top rail at each post and watch where the movement starts. A post that rocks at its base is loose at the deck frame. A rail that moves between solid posts has loose rail fasteners instead. Mark each problem spot, and keep people from leaning on the railing until it's fixed.
   Done

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2. Check for rotPush a flathead screwdriver or awl into the bottom of each loose post and into the rim joist around its fasteners. Wood that's soft, crumbly or lets the tip sink in easily is rotted. Rotted posts or framing can't be fixed by tightening; they need replacing, and rot in the rim joist calls for a deck contractor.
   Done

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3. Tighten existing fastenersIf the posts are held with bolts, tighten the nuts with a socket wrench. Replace any bolts, nuts or lag screws that are rusted badly. If a lag screw spins without tightening, it has stripped the wood and should be replaced with a through-bolt.
   Done

   Something went wrong?

   • The nut spins the bolt Hold the bolt head, or tap the carriage head so it bites the wood.

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4. Add through-bolts at the postsWhere a post is held only by nails or screws, drill two holes through the post and the rim joist, spaced apart vertically, and install 1/2-inch galvanized carriage bolts with washers and nuts on the inside. Tighten until the post is solid. Check your local code or a deck hardware maker's details, since many call for blocking or tension hardware behind the rim joist for full strength.
   Done

   Something went wrong?

   • The bit isn't long enough Drill from both sides, or use an extension or a longer auger bit.

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5. Re-fasten loose rails and balustersWhere the top or bottom rail has pulled away from a post, or balusters have popped their nails, drive exterior deck screws to reattach them, pre-drilling near board ends so they don't split. Replace any cracked balusters. Baluster gaps are commonly limited so a 4-inch ball can't pass through.
   Done

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6. Test it and protect the woodPush hard along the whole railing again. It should feel solid, with no rocking at the posts. Seal new holes and cut ends with a deck sealer or stain so water doesn't soak into them, and check the railing again each spring.
   Done

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Watch it done

DIY Fix Wobbly Railings (On a Deck or Porch)By The Honest Carpenter on YouTube. Their method may vary a little from ours.

Watch on YouTube

If it's the deck itself

If a deck board is cracked or loose, check our guide for replacing a deck board.

If an indoor stair railing is loose, there's a separate guide for tightening a loose stair railing.

Wobbly deck railing questions