Floorboard screws size for chipboard and timber boards

Updated: 21 October 2026

You are holding an 18 mm or 22 mm sheet, or softwood boards that still show the nail lines, and the search has mixed five products into one basket.

You are holding an 18 mm or 22 mm sheet, or softwood boards that still show the nail lines, and the search has mixed five products into one basket. Floorboard screws size is the diameter, the length for the board you measured, the thread that pulls the board down, and the drive your bit already fits. Prices and review files sit on the floorboard screws comparison. If you buy through our amazon.co.uk links, we may earn a commission at no extra cost to you. We used NHBC’s chipboard clause and those listings on 19 October 2026.

Our top picks

Badge	Product	Size	Thread	Drive	Note	Price	Offer
Best overall	Keple Keple floorboard screws, 3.9 x 58 mm	3.9 x 58 mm	Unclear	Square (SQ2)	5.5	about £18.99	View offer
Best value	fischer fischer Power-Fast II chipboard screws, 4.0 x 40 mm	4.0 x 40 mm	Full	Phillips	5.7	about £19.85	View offer
	Ulti-Mate Ulti-Mate floorboard screws, 4.2 x 50 mm	4.2 x 50 mm	Partial	Phillips and square	8.6	about £9.99	View offer

Best overall

Keple Keple floorboard screws, 3.9 x 58 mm

5.5/10about £18.99

View offer

Best value

fischer fischer Power-Fast II chipboard screws, 4.0 x 40 mm

5.7/10about £19.85

View offer

Rank 3

Ulti-Mate Ulti-Mate floorboard screws, 4.2 x 50 mm

8.6/10about £9.99

View offer

On this page

1.Measure the board before you pick a length
2.Diameter, thread and head
3.Drive and indoor finish
4.What to leave in the search

Measure the board before you pick a length

Measure the board before you choose a length. NHBC’s table, a new-home warranty rule rather than a statute, commonly uses 18 mm chipboard at 400–450 mm joist centres and 22 mm at 600 mm, for an imposed load stated as 1.5 kN/m². The same clause asks for at least a No. 8 and twice the board: 36 mm on 18 mm and 44 mm on 22 mm. Maker guides often use 45–50 mm and 55–60 mm. Add a carpet or a second layer only after you have measured that stack with a tape. Fix at no more than 300 mm along the supports, and leave at least 10 mm at a rigid upstand. A longer screw bought for luck is how a spare shank reaches a cable. Finding the joist comes first, on the how to screw down floorboards page.

Diameter, thread and head

Face-fix chipboard and softwood want about 4.0–4.5 mm. A 3.5 mm screw is the tongue-and-groove family, driven at an angle through a timber tongue, and it is the wrong only fixing on the face of 22 mm chipboard. That split is the chipboard or tongue-and-groove screws page. On these listings the named floorboard box is 4.2 x 50 mm and partially threaded, the tongue box is 3.5 x 45 mm, the bulk chipboard box is 4.0 x 40 mm and fully threaded, and the 3.9 x 58 mm box has thread fields that disagree. Use a small countersunk head if you will see or sand the floor.

Testsieger

Keple Keple floorboard screws, 3.9 x 58 mm

5.5/10about £18.99

View offer

Drive and indoor finish

Match Phillips, Pozidriv, Torx or square to a bit you own. They are not interchangeable. A worn bit in a fine head is how the head snaps in the last turns. Ulti-Mate listings claim a stick-fit bit, and reviews also say a bit was missing or that a Torx head chewed the bit, so keep a spare. Square drive on the 3.9 x 58 mm box needs the SQ2 bit the listing names. If a card does not name the drive, do not assume Pozidriv. A drill-driver with a clutch is the safer default: on 12 tongue-screw reviews an impact driver was blamed for sheared heads.

What to leave in the search

A mixed woodscrew assortment has no single length you can check against 18 mm or 22 mm. A decking screw is built for outdoor boards rather than a chipboard floor. A 4.0 x 25 mm woodscrew can share the word floor and still miss the joist once the head is flush. A snap-off kit does not state a diameter or a length, and a review says no head remains afterwards. That decision sits on the squeaky floorboard screws page. On these amazon.co.uk listings the boxes run from about £8.99 to £23.33. None of these amazon boxes shows a BS EN 14592 declaration.

Common questions

What length of screw do you need for 18 mm chipboard?

For 18 mm chipboard, NHBC’s published minimum is twice the board, which is 36 mm, and no smaller than a No. 8. Makers often suggest 2.5 times the thickness, so the practical buy is 45–50 mm. A 40 mm chipboard screw can meet the 36 mm minimum and still sit short of that practical band once the head is countersunk. Add length only for a carpet or a second layer you have measured. The screw still has to land in a joist.

What length do you need for 22 mm chipboard?

For 22 mm chipboard the same clause gives a minimum of 44 mm. The practical buy on UK size guides is 55–60 mm, so a 50 mm floorboard screw is on the short side and a 40 mm screw is below the minimum. Joist centres of 600 mm are the usual reason a domestic deck is 22 mm rather than 18 mm. Confirm the sheet with a tape before you treat a 58 mm box as the match.

Is a No. 8 the same as a 4 mm screw?

A No. 8 is the gauge NHBC names, and in this trade it means a screw of about 4.0–4.5 mm, not a promise that 4.2 mm and 3.9 mm are identical. A 3.5 mm screw is the slimmer tongue-and-groove family. Use about 4 mm when you are face-fixing chipboard or softwood boards. Use 3.5 mm when the head has to hide in a timber tongue.

Should the screw be partially threaded or fully threaded?

A partial thread lets the head pull the board down onto the joist, because the shank can slide through the board. A fully threaded chipboard screw needs a clearance hole through the board, or firm pressure, or it can jack the sheet and leave a squeak. Neither shape is a structural rating. These boxes do not show a BS EN 14592 declaration.

Is zinc-and-yellow an outdoor or stainless finish?

Zinc, including zinc and yellow, is an indoor coat. It is not stainless, and it is not a reason to use the screw in a wet room or on a deck outside. Blue passivated zinc is the same class of indoor plating. If a listing says both stainless and alloy steel, the card has not settled the metal, and the yellow colour does not settle it for you.

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