How do I stop my deck from wobbling?

A wobbly deck can be frustrating and dangerous. Thankfully, there are several ways to stop your deck from wobbling so you can enjoy your outdoor space safely.

What causes deck wobble?

There are a few common causes of deck wobbling:

• Rotting wood – If the wood making up your deck structure is rotting or decaying, it can become weak and unstable. This will lead to wobbling.
• Improper support – Decks need a solid foundation and structural support system. If the posts, beams, or joists are not properly supported, the deck can become shaky.
• Loose hardware – Nails, screws, and connectors (like joist hangers) can become loose over time, causing the deck to shift and move.
• Settling soil or eroding ground – If the ground under or around your deck begins to erode or sink, it can undermine the support system and lead to an unsteady deck.
• Too much bounce or give – Excessive flexing of the deck boards when walking on the deck can make it feel wobbly.

Inspect the deck structure

The first step in troubleshooting a wobbly deck is to thoroughly inspect the deck structure. Look for these common issues:

• Check for wood rot, cracks, or deterioration in the deck boards, posts, beams, and joists.
• Make sure all hardware connections are tight and secure.
• Look for loose, shifting, or uneven footings under posts.
• Check for levelness across the deck surface.
• Push on various components to check for soft spots or extra give.

As you inspect, take note of any areas that need to be repaired or reinforced. Addressing these weak spots is key to stopping the wobble.

Reinforce the structure

Based on your inspection, you may need to take steps to reinforce or stabilize your deck structure. Here are some options:

• Strengthen support posts – If posts are loose or sinking, use cedar shims to level them. Or you may need to redo footings.
• Add bracing – Extra cross bracing, knee braces, or blocking can shore up a shaky structure.
• Replace rotten wood – Remove and replace any rotting, cracked, or split wood.
• Bolster joints – Add metal plates, connector ties, or extra hardware at key joints.
• Install new footings – For serious settling issues, you may need to pour new footings for the support posts.

Properly reinforcing the underlying structure of your deck is the best way to stop wobbling long-term.

Tighten up hardware

A simple way to improve deck stability is to check and tighten all of the nuts, bolts, screws, and nails. Use these tips for tightening deck hardware:

• Inspect joist hangers and ledger connections first and tighten any loose screws or nails.
• Tighten any loose deck board screws or nails – be careful not to overtighten.
• Look for loose guardrail bolts, staircase stringer hardware, and other fasteners.
• Check foundation hardware – post anchors, concrete screw anchors, etc.
• Tighten up the hardware gradually in stages and recheck.
• Make sure fasteners are flush – do not overtighten.

Proper torque on all deck hardware reduces vibration and wobbling.

Address settling ground

If the ground around your deck is eroding or settling, it can undermine the support structure. Here are some ways to address ground issues:

• For serious settling, have new footings poured.
• Backfill settled areas under the deck with compacted gravel.
• Install an earth retention system like terraces or a retaining wall.
• Improve drainage around the deck to prevent further erosion.
• Lay down landscape fabric and gravel around the deck perimeter.

Restoring proper ground support is key if erosion is causing your deck to shift or sink.

Add supportive blocking

Adding strategic blocking between joists and beams can help stiffen up a wobbly deck:

• Cut 2x blocking to fit snugly between joists halfway along the joist span.
• Install crisscross blocking between perpendicular joists for maximum stability.
• Toenail blocking in place using 3-inch exterior screws.
• Check for loose joists at the ledger board and add double blocking.
• Use flat metal plates to connect blocking for a stronger connection.

Blocking helps reduce up and down deck movement that leads to wobbling.

Reinforce connections with hardware

There are special hardware products made to reinforce weak joints and prevent wobbling:

• Joist hangers properly support joists at the ledger.
• Joist repair hangers can be added between existing joists and beams.
• Galvanized joining plates strengthen multi-member connections.
• Deck connectors tie joists together and reduce side-to-side sway.
• Post anchors anchor posts solidly to footings or piers.

Upgrading the connectors is an easy DIY solution for a stable deck.

Reduce joist bounce

Excessive bounce or flex in deck boards as you walk across the deck can make it seem unstable. To minimize joist bounce:

• Make sure joists are sized adequately for the deck span.
• Reduce joist spacing to 16-inches on-center or less.
• Use thicker deck boards or firmer composite decking.
• Install rigid foam insulation between joists.
• Add supportive blocking between joists as needed.

With less joist flex, your deck will feel much more solid.

Replace rotten or cracked wood

Rotten or cracked wood is a common cause of wobbling. Here are some tips for replacing bad deck wood:

• Inspect wood carefully and probe with a screwdriver to find soft spots.
• Support beams safely before removing/replacing vertical posts.
• Remove rotted wood completely – down to solid material.
• Use treated lumber rated for outdoor use.
• Secure new wood tightly with bolts, not just nails.

Replacing worn or damaged wood members is key to permanently solving wobble.

Conclusion

A wobbly, unstable deck is not only annoying, but also a safety hazard. In most cases, you can improve deck stability by taking the following steps:

• Thoroughly inspect the structure and identify weak points.
• Reinforce the frame with extra bracing, blocking, posts, footings, etc.
• Tighten up all hardware connections properly.
• Replace any rotten, cracked, or split wood.
• Use hardware reinforcement products at weak joints.
• Reduce joist bounce and flexing with closer spacing, thicker deck boards, etc.

With the right repairs and modifications, you can eliminate annoying and dangerous wobbling and create a solid, stable deck surface for years to come.