Why does my chipboard upstairs floor creak and dip?
Chipboard flooring is a sheet deck, not a board floor, and it fails in its own particular ways — lost fixings, unsupported joints, swelling at the edges and a missing noggin under a sheet edge.
- Difficulty
- intermediate
- Time
- 1 hr 30 min
- Read
- 3 min
- Safety
- warning
Short answer
Chipboard creaks because a sheet has lost its grip on the joists or a sheet edge has no support beneath it. Screw the sheet down properly into every joist with coarse-thread flooring screws, and where an edge runs between joists with nothing under it, add a noggin. Swollen, crumbling edges have to be cut out rather than screwed down.
Most UK houses built since the 1970s have a tongued and grooved chipboard deck upstairs, laid in large sheets over the joists. It behaves nothing like a board floor: the sheets are big, they are meant to be glued and screwed, and every noise it makes traces to one of four causes.
Safety
What you'll need
- a cable and pipe detector
- coarse-thread chipboard or flooring screws
- a drill/driver
- timber for noggins (optional)
- waterproof PVA or a flooring adhesive (optional)
Step by step
- Find the joists and mark them.The original fixings show as a grid of screw or nail heads. Confirm with a detector. Chipboard decks are usually laid with the long edge running across the joists.
- Identify which of the four faults you have.Lost fixings — the sheet lifts and drops on the joist. Unsupported edge — the noise is right along a joint between two sheets, mid-bay. Swollen edge — the joint line is raised and crumbly, from a leak or a wet build. Squeaking tongue — two sheets rubbing at the joint.
- Re-fix lost fixings first.Coarse-thread flooring screws, driven into every joist at close centres — the sheet manufacturers state a spacing and it is closer than most people fix at, typically around 300mm along a joist and closer at the sheet edges.
- Do not use nails, and do not use plasterboard screws.Nails pull out of chipboard, and hardened plasterboard screws snap. A proper flooring screw with a coarse thread and a countersunk ribbed head is the fastener this deck is designed for.
- Add noggins under unsupported edges.Where a sheet edge falls between joists with nothing beneath it, cut short timbers to fit tightly between the joists, screw them through the joists at each end, and then screw the sheet edges down onto them. This is the single most effective repair on a chipboard floor.
- Deal with a squeaking tongue joint.Where two sheets rub, running a bead of adhesive into the joint from above will not reach. Lifting one sheet and gluing the joint properly does; so does screwing both sheets down harder either side, which stops the relative movement.
- Cut out anything swollen.Chipboard that has swollen with water does not recover, and it never regains its strength. Cut the affected area back to the nearest joists, add battens or noggins to support the new edges, and fit a piece of moisture-resistant flooring-grade board.
- Check the deck grade before replacing.Flooring chipboard is a specific grade with moisture resistance and a tongued and grooved edge. Ordinary chipboard from a sheet rack is not the same material and will fail.
If it doesn't work
Creak in the middle of a room, along a straight line
Cause: A sheet joint falling between joists with no noggin beneath it — Fix: Cut an access opening if needed, fit noggins between the joists under the joint, and screw both sheet edges down onto them.
Deck dips underfoot near a bathroom door
Cause: Swollen chipboard from a leak, usually a shower tray, a bath waste or a WC connector — Fix: Fix the leak first. Then cut the swollen material out completely and replace with moisture-resistant flooring board on new bearings.
Creak that moved after new carpet was fitted
Cause: The carpet fitter's gripper nails or staples have loosened the deck at the perimeter, or the old covering was holding a loose sheet flat — Fix: Screw the perimeter of each sheet down properly into the joists, keeping clear of the gripper line.
Whole floor feels lively across the room
Cause: This is joist deflection, not a deck fault — Fix: Different problem entirely — see the guide on a bouncy floor. Screwing the deck harder will not change it.