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Plasterboard screw buying guide: stud first, then box

Updated: 22 October 2026

You have 12.5 mm plasterboard, timber studs or a metal frame, and a search page that mixes coarse, fine, self-drilling and outdoor phosphate in one grid. This plasterboard screw buying guide keeps one order: what the stud is made of, how long the screw must be, which head and bit you already own, then the finish and the pack. The nine amazon.co.uk boxes, with prices in GBP, are on the [drywall screws comparison](/hub/screws-and-accessories/drywall-screws). Figures below are those listings, not a live checkout and not a lab pull-out test. You should leave knowing which card to open and which sentence on the card to ignore.

You have 12.5 mm plasterboard, timber studs or a metal frame, and a search page that mixes coarse, fine, self-drilling and outdoor phosphate in one grid.

Our top picks

Forgefix ForgeFix coarse 3.5 x 38 mm

Best overall

Forgefix ForgeFix coarse 3.5 x 38 mm
9.4/10about £2.57
View offer
SEQUAL SEQUAL fine 3.5 x 38 mm

Alternative

SEQUAL SEQUAL fine 3.5 x 38 mm
7.8/10about £9.99
View offer
Forgefix Forgefix 4.2 x 100 mm

Best value

Forgefix Forgefix 4.2 x 100 mm
8.6/10about £3.59
View offer
On this page
  1. 1.Timber stud or metal stud
  2. 2.Length after the stud
  3. 3.Bugle head, PH2 and black phosphate
  4. 4.Pack size and cards that disagree

Timber stud or metal stud

The first split is the stud. A coarse thread, usually 3.5 mm, with a sharp point and a black bugle head, bites timber. A fine thread with a needle point is the light-metal screw. British Gypsum’s phosphate sheet, to EN 14566, is for C studs under about 0.8 mm and I studs under about 0.6 mm. Knauf cites metal up to about 0.7 mm. Thicker steel needs a self-drilling point: Speedline cites over 0.9 mm up to 3 mm, and Knauf’s jack-point page cites 0.7 mm to 1.2 mm. A bullet that swaps the threads is a listing blur. The boxes are on coarse versus fine plasterboard screws.

Length after the stud

Add the board to the purchase, then buy the next stock length. British Gypsum’s FAQ, for their screws, asks for the board plus at least 25 mm into timber, or plus at least 10 mm into metal. A 12.5 mm board on timber is about 38 mm coarse. On light metal it is about 25 mm fine. A second 12.5 mm layer into timber wants about 50 mm if you keep 25 mm of purchase. Jiahezhi at M4 x 25 mm, £6.99, and Wavanta titled M4 x 30 mm, £9.99, fail that timber sum. The ForgeFix coarse 3.5 x 38 mm box of 200, at £2.57, matches a single 12.5 mm board on timber. The sums are on the plasterboard screw length page.
Forgefix ForgeFix coarse 3.5 x 38 mm

Testsieger

Forgefix ForgeFix coarse 3.5 x 38 mm
9.4/10about £2.57
View offer

Bugle head, PH2 and black phosphate

The head is a bugle, a curved underside that sinks just below the paper. A countersunk wood screw can tear the face. Where these boxes name a recess, the drive is Phillips, and a printed size is PH2. Pozi cams out. Black phosphate is the interior finish, corrosion class 1 on trade pages: a clean, dry room. EN 14566 is the screw standard, not a fire rating. Ignore a bullet that says the coating suits outdoors. The Jiahezhi card does that.

Pack size and cards that disagree

A box of 200 is a patch. A room or a ceiling wants 500 or 1,000. The ForgeFix 38 mm box is 200 at £2.57, and the title does not include a bit. ForgeFix’s page puts the Phillips bit in the 500 and 1,000 boxes. SEQUAL’s pieces field says 1 against 200. Heifix’s unit count says 500 against a title of 200. Wavanta pairs an M4 title with a 3.9 mm field. Under the Consumer Rights Act 2015 the goods should be as described. Which card survives is on best plasterboard screws.

Common questions

Do I buy coarse or fine first?
Buy the thread that matches the stud you can see. Coarse, usually 3.5 mm and black, is for timber studs, joists and battens. Fine, with a needle point, is for light-gauge metal, with British Gypsum citing C studs under about 0.8 mm and Knauf citing up to about 0.7 mm. Thicker steel needs a self-drilling point. A shop line about MDF is not a reason to mix the two boxes.
What length for 12.5 mm board on timber?
About 38 mm of coarse screw, so the board plus at least 25 mm into the timber. British Gypsum states that sum for their screws, and 38 mm is the stock size that meets it. In this set that is the ForgeFix coarse 3.5 x 38 mm box at £2.57. A 25 mm or 30 mm screw on the same board leaves too little in the stud. The metal-stud sum is different: about 25 mm of fine thread for the same 12.5 mm board.
Is a bugle head the same as a countersunk wood screw?
No. A bugle has a curved underside that pulls the head just into the paper. A countersunk wood screw has a flat cone that can tear the face of the board. If a drywall listing says countersunk in one line and bugle in another, do not assume they mean the same head. You still need the paper intact so the jointing compound has a face to key to, rather than a broken core.
Can I use black phosphate outside or in a wet room?
Not on the strength of a black colour. Phosphate on these screws is an interior finish for a clean, dry room. Trade pages that print a corrosion class put it at class 1. A bullet that says indoor and outdoor on a phosphate card, including the Jiahezhi listing here, is a claim to set aside. A wet room, or anything left in the weather, wants a coating that is stated for that use. Phosphate is not stainless, and a black screw is not a decking screw.
Is a 200-piece box enough for a room?
It is enough for a patch or a short run of wall. A full room, and a ceiling in particular, uses screws at closer centres and will empty a 200-piece box before the boards are up. Plan on 500 or 1,000 for a room. The £2.57 ForgeFix box is 200, which is a sensible first box for the 38 mm timber length, not a whole-house pack. Count the studs and the centres before you assume one small box will finish the job.

Related pages

How to screw plasterboard

Drywall screws

Best plasterboard screws: the top pick in this set

Coarse vs fine plasterboard screws: timber or metal

Plasterboard screw length: add the board, then size

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 listing lines captured on 19 October 2026. The high-street price band that day is a rule of thumb and is not one of these rows. There is no laboratory pull-out test.

  1. British Gypsum 45 mm drywall screw data sheet (retrieved 19 October 2026)
  2. British Gypsum, screw lengths for metal and timber (retrieved 19 October 2026)
  3. British Gypsum, screw fixing centres (retrieved 19 October 2026)
  4. Knauf UK plasterboard screws (retrieved 19 October 2026)
  5. Speedline fixings sheet, August 2022 (retrieved 19 October 2026)
  6. Homebuilding, screwing into plasterboard (retrieved 19 October 2026)
  7. Wickes plasterboard screws (retrieved 19 October 2026)