Bounce means a span somewhere is too long for the load. It is almost never the boards, which is why replacing boards on a bouncy deck changes nothing except the colour.
Diagnostic timeline
Work through these steps in order before booking a repair.
- 1
Mark where the bounce is worst and measure the joist centres from beneath if you can.
- 2
Check whether the pads under that area have settled or moved.
- 3
Listen for creaking at fixings, which indicates movement rather than deflection.
- 4
Rock a corner post if the deck is raised — bracing may be missing entirely.
Likely causes
Joist centres too wide
Especially common under composite boards, which need tighter spacing than softwood.
Bearers too far apart
The joists are fine; the supports beneath them are too widely spaced.
Pads settled
Slabs or pads sinking into unconsolidated ground leave sections unsupported.
Missing noggins
Without cross-bracing between joists, the frame twists rather than sharing load.
Fix options, full-width
Add intermediate joists or noggins
Spacing is marginalExtra timber into the existing frame stiffens it without a rebuild.
Add or reset supports
Pads have settledNew pads on a compacted base under the affected spans, and packing removed rather than added to.
Brace a raised deck
The structure swaysDiagonal bracing between posts converts a wobbly frame into a rigid one.
Rebuild the substructure
Spans are wrong throughoutFrame rebuilt to the board manufacturer's spacing — the only real fix when the original was under-specified.
Get this fixed properly
Free site visit across London and Hertfordshire, a written specification and a fixed price before anything starts.
Prevention
- Build to the board manufacturer's joist spacing, tighter for diagonal laying
- Compact the base properly before setting pads
- Brace anything raised above ground level
Frequently asked
Is a bouncy deck dangerous?
Bounce alone usually isn't, but sway on a raised deck is a structural concern and should be looked at.
Can bounce be fixed without lifting boards?
Sometimes from beneath on a raised deck; on a ground-level deck we usually lift a strip of boards.
Will heavier boards stop the bounce?
No. Deflection is a frame issue and heavier boards can make it slightly worse.
Do you survey existing decks?
Yes — we lift a section, probe the frame and give you an honest repair-or-rebuild answer.