Best Screws for Chipboard Flooring: Sizes, Spacing and Fixing Guide

The best screws for chipboard flooring have four features:

• They are hardened and countersunk.
• They are at least No. 8 gauge (about 4mm).
• They are long enough to be 2.5 times the thickness of the board.
• They are driven at no more than 300mm centres along every joist.
  

For 18mm boards that means 45mm to 50mm screws. For 22mm boards it means 55mm to 60mm screws. Get the length, gauge and spacing right, glue the joints, and a P5 chipboard deck has every chance of staying flat and quiet.

This guide covers:

• screw sizes for 18mm and 22mm boards
• how many fixings each sheet needs
• the fixing method that NHBC and the board manufacturers expect
• the mistakes behind most squeaky chipboard floors.

The Short Answer

• Screw type: hardened chipboard screws or dedicated flooring screws, countersunk, No. 8 (4mm) gauge or thicker.
• 18mm P5 chipboard: 4.0 x 45mm or 4.0 x 50mm screws, on joists at no more than 450mm centres.
• 22mm P5 chipboard: 4.0 x 55mm or 4.0/4.5 x 60mm screws, on joists at up to 600mm centres.
• Spacing: 300mm maximum along each joist, with every fixing at least 9mm in from a board edge.
• Glue: bond the tongue and groove joints and the joist tops. Screws hold the floor down; glue stops it creaking.

What Screws Should You Use for Chipboard Flooring?

Use countersunk chipboard screws or purpose-made flooring screws. Avoid drywall screws and odd wood screws from the bottom of the toolbox.

NHBC Standards 2025, Chapter 6.4 sets the minimums for chipboard flooring fixings:

• Screws: no smaller than No. 8 and at least twice the board thickness.
• Nails: flat-headed ring shank nails at least 2.5 times the board thickness.
  

A No. 8 screw is roughly equivalent to a 4mm metric screw, according to Engineering ToolBox’s metric to imperial screw chart. That makes 4.0mm the smallest diameter worth buying. A 4.5mm or 5mm screw is fine too. You gain grip in the joist, but you need a slightly bigger pilot hole in the board.

A good chipboard flooring screw has:

• Hardened steel. Driving 60mm of screw into a dense joist puts real torque through the shank. A soft screw can snap or strip its head.
• A countersunk head, ideally with nibs underneath. These cut a clean seat, so the head finishes flush without tearing a crater in the board.
• A deep, coarse thread. Particleboard has less fibre strength than solid timber, so the thread needs to bite hard.
• A Pozi or Torx drive. You will drive a couple of hundred screws in a single room, and a drive that doesn’t cam out saves hands and heads.
• Corrosion protection, such as zinc and yellow passivate. P5 is the moisture-resistant grade NHBC requires for floors, and a bare steel screw will rust in a damp build.

Chipboard Screws vs Dedicated Flooring Screws

Both work on P5 decking. The difference is how far the thread runs up the shank.

Most joiners fix chipboard floors with ordinary hardened chipboard screws. These are zinc and yellow plated, Pozi drive, with a deep thread made for chipboard, MDF and softwood. In the 45mm to 60mm lengths that flooring needs, they are usually fully threaded.

A fully threaded screw grips the board and the joist at the same time. That creates a risk:

• If there is a gap between board and joist when the thread takes hold, the screw locks that gap in rather than closing it.
• The result is a board that clicks underfoot.
• The fix is simple: stand on the board next to the fixing as you drive it, or drill a clearance hole through the chipboard so the thread only engages the joist.
  

Dedicated flooring screws usually have a plain section of shank under the head. It slides through the board, so the head pulls the chipboard down tight as the thread draws into the joist. They cost more per box. Some also carry low-friction coatings that make driving long screws less tiring.

Which should you choose?

• Large new-build deck laid by one person: the pull-down action of a part-threaded flooring screw earns its price.
• Bedroom or loft where you can put your weight on each board: a quality fully threaded chipboard screw does the same job for less.

Screws vs Ring Shank Nails

NHBC allows both, but screws suit occupied homes better:

• There’s no hammering above a plastered ceiling.
• Boards can come back up later for access to pipes and cables. A nailed floor rarely comes up without damage.

What Size Screws for 18mm and 22mm Chipboard Flooring?

Use 45mm to 50mm screws for 18mm chipboard and 55mm to 60mm screws for 22mm chipboard. These lengths match the 2.5 times rule NHBC applies to nails, which is stricter than the 2 times minimum it sets for screws. You meet both.

The board manufacturer agrees. West Fraser’s current CaberFloor P5 installation guide specifies a 55mm chipboard screw, which is exactly 2.5 times a 22mm board.

Joist centres from NHBC Table 7 and West Fraser’s CaberFloor guidance. Thread depth is the screw length minus the board thickness.

The last column shows why the extra length matters:

• On 22mm board, NHBC’s 44mm minimum leaves 22mm of thread in the joist.
• A 55mm screw puts 33mm in, which is half as much grip length again for a few pence more per box.
  

Board thickness follows joist spacing, not the other way round:

• NHBC’s decking table allows 18mm P5 only at 400mm or 450mm centres. At 600mm centres it requires 22mm.
• West Fraser recommends 22mm CaberFloor for all first floor and above applications, to satisfy building control and NHBC. It lists maximum spans of 450mm for 18mm board and 600mm for 22mm, for domestic use only.

How Far Apart Should Chipboard Flooring Screws Be?

Space screws no more than 300mm apart along every joist and supported edge. That is the NHBC maximum.

West Fraser’s guidance adds two details:

• Fix at 200mm to 300mm centres along board edges and 300mm elsewhere.
• Keep every fixing at least 9mm in from the panel edge.

On a standard 2400 x 600mm tongue and groove board, West Fraser translates this into 3 fixings across each short end and 2 at each intermediate joist. If you glue the boards to the joists with its PU adhesive, it cuts that to one fixing per joist.

Calculated from West Fraser’s published fixing pattern. Its installation guide asks for 16 fixings on boards that meet the perimeter wall, even when glued.

Worked Example: How Many Screws for a Bedroom?

Take a 4.0m x 3.6m bedroom decked in 22mm P5 on joists at 600mm centres.

1. Boards: the floor area is 14.4m² and each 2400 x 600mm board covers 1.44m², so you need 10 boards. Allowing roughly 10% for cuts takes that to 11.
2. Screws: fixing with screws only, 11 boards x 12 fixings = 132 screws.
3. What to buy: a box of 200 at 4.0 x 55mm or 60mm. The spares cover misses, noggins and an access panel over the stopcock.

Gluing barely changes the screw count in a room this size. Most boards touch a wall, and West Fraser still wants 16 fixings on those perimeter boards. The payoff from glue is a quieter floor, not a cheaper one.

How to Screw Down Chipboard Flooring: Step by Step

1. Condition the boards for 48 hours. Stack them flat in the room where they’ll be laid so they settle at the moisture content they’ll live at. West Fraser’s installation guide asks for this.
2. Check the joists are dry. The same guide says joists should be dry and boards should never be laid in wet conditions. Wet joists shrink as they dry and pull away from the boards, and that is where creaks begin.
3. Find the services before you fix anything. Mark pipe and cable runs on the joist tops.

• Under BS 7671, a cable passing through a joist should sit at least 50mm below the top of it, as SELECT’s guide to Wiring Regulations group 522.6 sets out.
• A 60mm screw through 22mm board goes only 38mm into the joist, so correctly installed cables are clear.
• Pipes or cables notched into the top of a joist are not clear.

4. Lay the long edges across the joists and stagger the joints. NHBC requires tongue and groove boards to run with their long edges at right angles to the joists. Short edges must land on a joist or nogging.
5. Glue as you go. Run adhesive along the joist tops and into every tongue and groove joint.

• NHBC calls for PVAc adhesive on these joints.
• West Fraser recommends its flexible PU adhesive, which it says lets the board move with the joist and is five times stronger than nails.

6. Leave an expansion gap. Keep at least 10mm between the boards and every wall, and allow 2mm per metre run on larger floors. NHBC and West Fraser agree on both figures, and the skirting hides the gap.
7. Lay text side up, then pilot and drive. West Fraser says boards laid upside down make a weaker floor, even when glued.

• Drill a pilot hole. With fully threaded screws, make it a clearance hole through the chipboard.
• Stand on the board beside each fixing and drive the head flush or just below the surface.
• A head buried deep has crushed the particles it was meant to clamp.

8. Fix the perimeter, then the field. Keep to 300mm maximum centres along each joist and at least 9mm from board edges. Snap a chalk line along each joist centre first so no screw misses.

Why Chipboard Floors Squeak (and How to Stop It)

Most chipboard floor squeaks come from movement: between a board and a joist, or between two boards at a joint. More screws rarely cure it. The right screws, plus glue, plus proper gaps, prevent it.

The usual causes:

• Joist shrinkage. Joists dry out once the heating goes on. If the boards aren’t glued, a gap opens and the board rides up and down the screw shank with every step.
• Screws that miss the joist. A screw that clips the edge of a joist, or lands in the void beside it, holds nothing.
• Fully threaded screws driven into a gap. The thread locks the gap in place, as covered above.
• Swelling against a wall. Chipboard grows as it takes on moisture, and a board butted hard against a wall has nowhere to go but up.

West Fraser’s published figures show how much movement to expect:

• A 3% rise in moisture content increases board length and width by about 0.1%.
• Boards typically sit at 9% to 12% in an intermittently heated home and up to 15% in an unheated building.

Now apply that to a real room. A floor laid at 9% that climbs to 15% while the house is empty over winter grows by about 0.2%. Across a 4m room, that’s 8mm. It’s exactly why the 2mm per metre gap exists, and why a floor laid tight to the plaster lifts or creaks by spring.

Common Mistakes When Fixing Chipboard Flooring

• Laying 18mm board on 600mm joists. NHBC doesn’t allow it, and the floor will feel springy underfoot.
• Using screws that are too short. A 40mm screw in 22mm board leaves 18mm in the joist, below even NHBC’s 44mm minimum.
• Fixing too close to the edge. Screws within 9mm of a board edge can burst the chipboard and hold nothing.
• Laying boards text side down. West Fraser states the floor will not be as strong, whatever adhesive you use.
• Laying straight off the lorry. Skip the 48-hour conditioning and the boards do their moving after they’re fixed, not before.

Frequently Asked Questions

What type of screws are best for chipboard flooring?

Hardened, countersunk chipboard or flooring screws of at least No. 8 (4mm) gauge, 2.5 times the board thickness in length. Part-threaded flooring screws pull boards down on their own. Fully threaded chipboard screws do the same job if you stand on the board while driving them or drill a clearance hole first.

What size screws for 18mm chipboard flooring?

Use 4.0 x 45mm or 4.0 x 50mm screws. 45mm is 2.5 times the board thickness. NHBC’s absolute minimum is 36mm, but that leaves only 18mm of thread in the joist.

What size screws for 22mm chipboard flooring?

Use 4.0 x 55mm or 4.0/4.5 x 60mm screws. West Fraser’s current CaberFloor P5 installation guide specifies a 55mm chipboard screw, and NHBC’s minimum is 44mm.

Do you need to pre-drill chipboard flooring?

Pre-drilling is good practice. A pilot hole stops the board bursting near edges and helps the head sit flush. With fully threaded screws, a clearance hole through the chipboard also lets the screw pull the board tight to the joist.

Should you glue and screw chipboard flooring?

Yes. NHBC expects tongue and groove chipboard to be glued to the joists and at every joint. West Fraser says gluing lets the board move with the joist rather than against the fixings, which is what stops creaks forming as joists dry out.

Is P5 chipboard waterproof?

No. P5 is moisture resistant, made to cope with humid conditions and occasional wetting during a build, but West Fraser is clear it is not waterproof. Wipe up standing water straight away, and never lay boards in wet conditions.

The Bottom Line

Screw choice is the easy part of a chipboard floor: No. 8 gauge minimum, 2.5 times the board thickness, and 300mm centres along every joist. The flat, silent result comes from what surrounds the screws: dry joists, glued joints, a 10mm perimeter gap and every board pulled tight before it’s fixed.

Before you order, measure your joist centres, choose 18mm or 22mm board to suit, and buy a box of screws big enough to cover misses and noggins. If you’re still deciding on board, our comparison of MDF vs chipboard explains where each sheet belongs. You’ll find more flooring guides on UK Construction Blog. When the job’s done, check what can and can’t go in a skip before you book one for the offcuts.