Gyproc Drywall Screw 3.5 x 25 mm - Board to Metal (Pack of 750)

• Manufacturer: Gyproc (Saint-Gobain)
• Product: Drywall screw — board to metal
• Size: 3.5 x 25 mm
• Pack: 750 pieces
• Fine thread with a sharp point — designed to bite into GI steel sections
• Bugle head: Sinks into the board without tearing the paper face
• Suits a single layer of 12.5 mm board on a metal grid
• Please note: Not for timber framing — that needs a coarse-thread screw

Gyproc Drywall Screw 3.5 x 25 mm is the board-to-metal fixing for plasterboard onto a GI ceiling or partition grid, supplied in a box of 750.

The phrase board to metal is the most important thing on this listing, because drywall screws come in two thread types that look almost identical in a box and behave completely differently. A board-to-metal screw has a fine thread and a sharp point designed to cut into galvanised steel sections. A board-to-wood screw has a coarse thread for timber framing. Drive a coarse wood screw into a GI section and it spins without gripping or fails to pull the board tight — and you will not discover it until the ceiling is up and moving.

The bugle head is the other defining feature, and it is why drywall screws exist as a separate category at all. The underside of the head is curved rather than flat, so as it sinks it compresses the paper face and beds in smoothly instead of cutting through it. A flat countersunk head slices the paper, and once the paper is cut the screw has almost nothing to hold onto.

25 mm is the right length for a single layer of 12.5 mm board. The working rule is that the screw must pass through the board and penetrate the steel section by around 10 mm to grip properly — 12.5 mm of board plus roughly 10 mm of penetration lands squarely at 25 mm. For a double layer of board, this is too short and a longer screw is needed.

Technical Specifications

Applications

1) What is the difference between board-to-metal and board-to-wood screws?

The thread, and it decides whether the screw grips at all. Board to metal — these — have a fine thread and a sharp point that cuts into GI steel sections. Board to wood screws have a coarse thread for timber. A coarse screw in a steel section spins without gripping; a fine screw in timber strips the hole. They look similar in a box and are not interchangeable, so check which framing you have.

2) How deep should I drive them?

Just below the paper surface, without tearing the paper. That is the whole technique. The paper face is what carries the load — once the head breaks through it, the screw holds almost nothing, and that fixing will eventually show as a popped head through your finished ceiling. Use a depth-setting nosepiece or dimpler bit, which stops the driver automatically and is far more reliable than judging depth by feel several hundred times overhead.

3) Is 25 mm the right length for my job?

For a single layer of 12.5 mm board on a metal grid, yes. The rule is that the screw should pass through the board and penetrate the steel by around 10 mm — 12.5 plus 10 lands at about 25 mm. For a double layer of board, or thicker board, 25 mm is too short and you need a longer screw.

4) How many will I need?

Follow the screw spacing specified for your ceiling system rather than a rule of thumb, since under-fixing causes sag and cracking along joints. As a rough planning figure only, budget around 30 to 40 screws per 4 x 6 ft board, which puts a 750 box at roughly 20 to 25 boards. Check that against your actual specified spacing before ordering.

5) Can I use these outdoors or in a bathroom?

No — these are an internal dry-use fixing. External and wet conditions need a screw with a corrosion-resistant coating rated for them, used with a board suited to those areas. Plain drywall screws in a damp environment corrode and stain through the finish.

1. Return within 24 hours of delivery for:
   • Damaged or defective product
   • Wrong or missing item
2. Product cannot be returned once installed or used
3. Refer to Refund Policy for complete details

Please check the size and that the box is the board-to-metal type on delivery, before starting work.