Why Is My Decking Bouncy When I Walk On It

Bouncy decking means the subframe below the boards is underbuilt, failing or rotten. Plex Group explains the causes and what a proper repair looks like across Worcestershire and the Cotswolds.

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Joists Spaced Too Far Apart or Undersized

Standard softwood decking boards need joists at 400mm centres at most, and 300mm centres where boards run diagonally or where composite boards are used. Many decks are built with joists at 600mm centres, the spacing the builder had in their head from stud walls. The boards then span further than they were designed to and deflect underfoot. Undersized joist timber causes the same problem over longer spans. The fix is not more screws through the boards. The fix is more support underneath them.

Post Failure Below Ground

The whole deck sits on its posts, and the posts are the part you cannot see. Posts concreted in without ground contact rated timber rot at the point where they leave the soil, usually within eight to twelve years. Posts sat on paving slabs or bare soil sink unevenly, and spiked repair supports driven in beside a failing post rarely hold because they never reach undisturbed ground. When one post drops even ten millimetres, the beam above it hangs unsupported and the whole corner of the deck bounces. If the movement is worse in one area than another, failed support below ground is the most likely cause.

No Noggins and a Beam Spanning Too Far

Joists need bridging, known as noggins, fixed between them to stop them twisting and to share load across the frame. A frame without noggins works as a set of individual planks rather than a single structure, so every footstep loads one joist at a time. The same applies to the main bearers. Where a single beam has been stretched between posts set too far apart, the beam itself flexes and the deck moves as one surface.

Rot in the Frame from Poor Ventilation and Ground Conditions

Ground conditions across our area work against deck frames in different ways. In the Vale of Evesham and on the clay soils around Cheltenham, the ground swells in winter and shrinks in summer, which rocks concrete pads and loosens post fixings year after year. On the limestone brash of the Cotswold wolds the soil drains freely but is often shallow, so pads bear at inconsistent depths and settle unevenly. In older gardens around Broadway and Winchcombe, established tree roots lift and tilt pads long after the deck was built. Add a frame built tight to the ground with no airflow beneath it and the joists stay damp, soften and lose their stiffness long before the boards on top show any sign of trouble.

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Signs Your Deck Frame Needs Attention

  • Visible flex in the boards when you walk across the middle of the deck
  • One corner or edge noticeably softer than the rest
  • Gaps opening between the deck and the house wall or between frame and posts
  • Screws or fixings working proud of the boards
  • A musty smell or dark staining at board ends and around fixings
  • Posts that move when pushed by hand
Can I fix bouncy decking by adding more screws?

No. Screws fix boards to joists, and the bounce is in the joists and the structure below them. Adding fixings can tighten a rattling board but it will not remove flex caused by joist spacing, span or post failure.

How far apart should decking joists be?

For standard softwood boards laid square, 400mm centres is the maximum. Diagonal boards and most composite boards need 300mm centres. Anything wider than that will deflect underfoot regardless of board thickness.

Is bouncy decking dangerous?

It can be. Bounce means the structure is deflecting beyond its design limit, and if the cause is rot or post failure the deck can drop suddenly under load. A deck used for seating, hot tubs or gatherings should be inspected as soon as movement is noticed.

Do you repair decking across Worcestershire and Gloucestershire?

Yes. Plex Group repairs and rebuilds decking across Worcestershire, Gloucestershire, Oxfordshire, and Warwickshire, including Evesham, Pershore, Cheltenham, Winchcombe, Broadway, and Stow-on-the-Wold.

How Plex Group Fixes Bouncy Decking

We start with a full site assessment. That means lifting boards to inspect the joists, checking joist centres and spans against the board type, probing posts at ground level for rot and checking pads and footings for settlement. Where the frame is sound but underbuilt, we add joists to close the centres to 400mm, fit noggins throughout and sister weak joists with new C24 timber. Where posts have failed, we excavate and set new ground contact rated posts in concrete to a proper depth, never spiked repair supports. Where rot has taken hold, we rebuild the subframe on a ventilated design with a membrane over the joists before the boards go back down. Plex Group repairs and rebuilds decking across Worcestershire, Gloucestershire, Oxfordshire, and Warwickshire.

Conclusion

A bouncy deck is always fixable once the cause is identified. Plex Group assesses and repairs decking across Worcestershire, Gloucestershire, and the Cotswolds. Get in touch to arrange a site assessment.

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Why Is My Decking Bouncy When I Walk On It

Bouncy decking means the subframe below the boards is underbuilt, failing or rotten. Plex Group explains the causes and what a proper repair looks like across Worcestershire and the Cotswolds.

Read more

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