How do I fix something to a metal stud wall?

Metal stud partitions are now standard in flats, extensions, offices and much new housing. They look identical to a timber stud wall from the front and they behave very differently: the framing is thin cold-formed steel that twists rather than resists, and it will not hold a wood screw at all.

Safety

What you'll need

• A strong magnet, for finding studs
• A cable and pipe detector
• Fine-thread self-drilling screws
• Cavity fixings suitable for a shallow void (optional)
• Plywood for a pattress, plus screws (optional)

Step by step

1. Find the studs with a magnet.Run a small strong magnet over the wall and it will stick over every stud and every board screw. This is faster and more reliable than any electronic detector, and it also maps the screw line so you can see the stud spacing.
2. Confirm what you have found.A regular vertical line of magnetic points at 400 or 600mm centres is a stud. Isolated points can be pipe clips or a noggin bracket. Check top and bottom for a track running horizontally at floor and ceiling.
3. Check for services before drilling anything.The web of each stud has punched holes for cables, and cables therefore run horizontally at unpredictable heights. A detector plus caution; if in doubt, drill only to board depth.
4. Understand what a metal stud will hold.The steel is typically 0.5 to 0.7mm thick. A screw into it engages one or two thread turns. That is decent in shear — a load hanging down the wall — and poor in pull-out. It is not equivalent to a timber stud.
5. Use fine-thread self-drilling screws into the stud.Coarse timber threads simply strip thin steel. A fine-thread drywall screw or a small self-drilling screw cuts and holds. Do not over-torque: the moment it strips, that hole is finished.
6. Use a cavity fixing between studs for light items.Self-drive plugs, metal hollow-wall anchors and gravity toggles all work in the board itself. Check the void depth first — a metal stud partition is often shallower than a timber one and long-armed spring toggles may not open.
7. Fit a pattress for anything heavy.A piece of 18mm plywood screwed through the board into two or more studs, with the item then fixed to the plywood. This spreads the load into the frame and is the standard trade answer for televisions, radiators and wall units on steel framing.
8. Use purpose-made steel-stud fixings where a pattress will not do.Fixings exist that clamp through the stud web or that spread load between studs. They are worth buying for a single heavy item where the wall must stay flat.
9. Never rely on a single point on one stud.A C-section stud is thin and open on one side, so a heavy point load makes it twist. Spread the fixing over two studs or over a pattress.

Tips

• If you are building the wall, put timber noggins in at every height you might ever fix at — behind the TV, the radiator, the towel rail, the wall units — and photograph them before boarding.
• Sockets and switches in a metal stud wall sit in dry-lining boxes that grip the board itself. They are not a fixing point for anything.
• A magnet on a piece of string is the cheapest and most reliable stud detector there is, on a metal stud wall and on a boarded timber one.

Common mistakes

• Using coarse timber screws into a metal stud — The thread pitch is far too coarse for 0.6mm steel. It strips instantly, and the hole is then useless because the screw has removed the material it needed.
• Assuming a stud detector reading means timber — Detectors report density, not material. On a steel-framed wall the reading is a stud, but it is not a stud that will take a wood screw.

If it doesn't work