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Screws for chipboard flooring on 18 mm and 22 mm P5

Updated: 22 October 2026

You have 18 mm or 22 mm P5 tongue-and-groove in the room, and a 30 mm furniture screw is sitting in the same basket as a floorboard box. Screws for chipboard flooring are a length and a clamp, not a general carcass screw. Southern Timber’s rule is the one this page uses: pilot, Pozidriv No. 8 or equivalent, length 2.5 times the board thickness. The boxes and GBP prices are on the [chipboard screws comparison](/hub/screws-and-accessories/chipboard-screws). How to set the clutch stays on the [how to screw into chipboard](/hub/screws-and-accessories/chipboard-screws/sub/chipboard-screws-how-to-drive) page. A qualifying purchase can earn a commission at no extra cost to you. P5 is moisture resistant, not waterproof.

You have 18 mm or 22 mm P5 tongue-and-groove in the room, and a 30 mm furniture screw is sitting in the same basket as a floorboard box.

Our top picks

fischer fischer Power-Fast II 5.0 x 60 mm

Best overall

fischer fischer Power-Fast II 5.0 x 60 mm
7.4/10about £4.57
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SEQUAL SEQUAL 5 x 60 mm

Alternative

SEQUAL SEQUAL 5 x 60 mm
7.7/10about £12.99
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Ulti-Mate Ulti-Mate floorboard 4.2 x 50 mm

Alternative

Ulti-Mate Ulti-Mate floorboard 4.2 x 50 mm
7.6/10about £9.99
View offer
On this page
  1. 1.18 mm and 22 mm are different lengths
  2. 2.Clamp the board, do not jack it open
  3. 3.What these listings can and cannot do on a floor
  4. 4.Squeaks, glue and when to stop

18 mm and 22 mm are different lengths

Eighteen millimetres times 2.5 is 45 mm, and the practical screw around that sum is about 50 mm. Twenty-two millimetres times 2.5 is 55 mm, so the band is about 55–60 mm. Southern Timber states both 18 mm and 22 mm P5 as 2400 x 600 mm tongue-and-groove. A 50 mm screw that is right on 18 mm is short on 22 mm. A 30 mm screw fails both sums. Southern Timber’s pattern is four fixings on the panel ends and three at intermediate joists. A tighter spacing from another article is not treated as checked fact.

Clamp the board, do not jack it open

A flooring screw has to pull the board down onto the joist. A part thread, or a screw with an upper thread and a shank that can slide through the board, does that. The thread bites the joist and the board is free to close the gap. A full thread bites the chipboard as well. A DIYnot discussion of this joint says the thread in the top board can hold the board off the joist, so you drive harder and the gap stays. More torque then shears the head. Yellow zinc on a floorboard screw in this set is an indoor plating. A wet room, a balcony and a coastal deck are outside it. P5 is moisture resistant, not a marine sheet.
fischer fischer Power-Fast II 5.0 x 60 mm

Testsieger

fischer fischer Power-Fast II 5.0 x 60 mm
7.4/10about £4.57
View offer

What these listings can and cannot do on a floor

The Ulti-Mate 4.2 x 50 mm at about £9.99 is the floorboard listing, 200 in the title, for chipboard, plywood and floorboards. Reviews describe a tight floor, and also sheared heads, a missing Stick-Fit bit, and short packs. The field says partial thread. One review says the thread runs to the head. Fifty millimetres is the 18 mm length. It is short for 22 mm P5. The fischer 5.0 x 60 mm box of 100 at about £4.57 meets the 22 mm sum only on the arithmetic. The title says TX and full thread. A bullet says PZ and part thread. A 60 mm part thread would clamp. A full thread needs a clearance hole. Diameter and drive are the chipboard screws buying guide. The SEQUAL M5 x 60 mm is fully threaded Pozidriv, so it still needs that hole.

Squeaks, glue and when to stop

A squeak is movement between board and joist, or a fixing that no longer holds them. Screws alone do not promise silence. Follow the glue class your board supplier states. Extra screws beside existing nails are the DIY Doctor approach for a local squeak, after you have checked for cables and pipes. Stop when the head is flush. If several screws in a new box shear, the box is the limit. A title count of 200 and 42 in the carton will not finish a room.

Common questions

What length is 2.5 times 18 mm, and what length is 2.5 times 22 mm?
Two and a half times 18 mm is 45 mm, and the practical screw here is about 50 mm. Two and a half times 22 mm is 55 mm, so the band is about 55–60 mm. Southern Timber states that rule for P5, with Pozidriv No. 8 or equivalent. A 30 mm screw matches neither thickness.
Is a 50 mm screw enough for 22 mm P5?
It is short of the 2.5-times sum. After 22 mm of board, a 50 mm screw has less left in the joist than it has under 18 mm board. Use about 55–60 mm for 22 mm if the thread can still clamp. In this set, 50 mm is the 18 mm length.
Do I want a full thread or a screw that clamps the board to the joist?
You want a screw that clamps: a part thread, or an upper thread with a shank that lets the board slide down. A full thread can grip the chipboard and hold it off the joist. A clearance hole is the workaround if you already own full-thread screws.
Which box in this set is sold as a floorboard screw, and what do its reviews say?
The Ulti-Mate 4.2 x 50 mm at about £9.99 is the floorboard listing, 200 in the title, for chipboard, plywood and floorboards. Reviews describe a tight floor, and also sheared heads, a missing Stick-Fit bit, and short packs. The field says partial thread. One review says the thread runs to the head. Look at a screw before you board a room.
Will screws alone stop a squeak, or does the glue line matter?
Screws pull board to joist. They do not fill a dry tongue that rubs. Southern Timber specifies BS EN 204 class D3 for the tongue-and-groove. Another publisher asks for D4 and tighter centres. Use the class your board supplier states. Extra screws beside old nails can help a local creak once you know the joist is under the pilot and the services are clear.
Is P5 waterproof?
No. P5 is moisture resistant chipboard, not a waterproof or marine sheet. It is the usual flooring grade in the Southern Timber description of 18 mm and 22 mm panels. Yellow or blue zinc on the screws in this set is an indoor plating. A wet room or an exposed deck needs a different board and a different fixing.

Related pages

Pozidriv vs Torx screws

Chipboard screws

Best chipboard screws: the top pick and who skips it

Chipboard screws buying guide: diameter then length

How to screw into chipboard: bit, clutch, and stop

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are the amazon.co.uk lines in the display file. There is no laboratory test and no withdrawal value. A corrosion class stated for a different TIMCO SKU is not applied to the Solo box. ETA and EN 14592 citations are not copied onto unbranded assortments.

  1. Screwfix screws buying guide (retrieved 22 October 2026)
  2. TIMCO C2 Strong-Fix 5.0 x 50 mm (retrieved 22 October 2026)
  3. Southern Timber chipboard (retrieved 22 October 2026)
  4. fischer UK Power-Fast II (retrieved 22 October 2026)
  5. ETA-19/0175 (22 September 2025) (retrieved 22 October 2026)
  6. Shop4Fasteners, Pozidriv vs Phillips (retrieved 22 October 2026)
  7. SENCO UK chipboard screw (retrieved 22 October 2026)