How do I tell what my wall is made of before I drill it?

Tapping, a bradawl, and the colour of the dust — the quick tests that tell you whether you are drilling brick, block, plasterboard or lath before you commit.

Difficulty: beginner
Time: 10 min
Read: 3 min

Short answer

Tap it: solid walls are dull and dead, stud walls sound hollow between the studs. Push a bradawl into an inconspicuous spot — 12mm and then void means plasterboard, 12mm and then resistance forever means solid. The dust confirms it: red or pink is brick, grey is block or concrete, white and fluffy is plasterboard, grey with horse hair is lath and plaster.

Almost every fixing failure starts with a wrong assumption about the wall. Two minutes of testing decides the drill, the bit, the fixing and the safe load, and it costs nothing.

What you'll need

bradawl or thin nail
stud detector (optional)
cable and pipe detector

What a fixing meets in a solid wall and in a stud wall

Step by step

Tap across the wall with your knuckle.Solid masonry gives a dead, dull sound everywhere. A stud wall rings hollow between studs and goes dull at intervals of roughly 400 or 600mm where the studs are.
Check the age and position of the wall.External walls in a house are almost always masonry. Internal walls in anything post-1960 are commonly studwork. Pre-1930s internal walls are frequently lath and plaster.
Push a bradawl into a hidden spot.Behind a radiator, low on a wall or where a picture will hang. Twelve millimetres of easy resistance then a sudden void is plasterboard on studs. Hard resistance from a few millimetres in is masonry.
Drill a small test hole and look at the dust.White or pale grey powder that smells of chalk is plasterboard. Pink or red grit is brick. Fine mid-grey is dense block or concrete. Pale sandy grey that drills very fast is aerated block.
Watch for horse hair.Grey dust containing coarse hair fibres and small splinters of timber means lath and plaster. It needs a different approach entirely.
Use a detector to map the studs.Once you know it is studwork, find the studs before deciding anything. A fixing into a stud is worth many times a fixing into board.
Check for cables and pipes regardless.Every wall type can hide services. Scan the area, and think about what is above and below — sockets, switches, taps and boilers all imply runs.
Look at the plaster depth on masonry.Modern masonry usually carries 12 to 15mm of plaster; older walls can carry much more. Your fixing has to reach past all of it into solid material.

Tips

Dust colour is the most reliable single test, and a 4mm hole in a hidden spot tells you everything.
A wall can be more than one thing: a dry-lined masonry wall is plasterboard dabbed onto brick, with a 20 to 30mm void behind it.
If a wall sounds hollow but a detector finds no studs at regular spacings, suspect dry lining on masonry rather than a stud wall.

Common mistakes

Assuming an internal wall is brick because the house is old — Older houses use lath and plaster and later studwork extensively for internal partitions. The fixing that works in brick tears straight out of both.
Treating dry-lined masonry as a stud wall — There is a void behind the board but the studs a detector reports are not there. Cavity fixings hold poorly in this build-up; a long fixing through into the masonry behind is the right answer.

If it doesn't work

Drill goes in easily then hits something hard

Cause: Plasterboard skim over masonry, or dry lining — Fix: Keep going with the appropriate masonry bit and treat it as a solid wall with a deeper plaster layer.

Wall sounds hollow but a plasterboard fixing spins

Cause: Lath and plaster rather than plasterboard — Fix: Look at the dust for hair and timber splinters, and fix into the studs behind or use a spreading cavity fixing.

Detector reports studs everywhere

Cause: Foil-backed board, metal studs, or dense reinforcement confusing the detector — Fix: Cross-check by tapping and by drilling a small exploratory hole where it can be filled.

Questions people ask

How thick is plasterboard usually?

Twelve and a half millimetres for walls and ceilings in most British houses, and nine and a half on some older or lightweight work. Two layers are common where fire or sound performance is required.

What are metal studs?

Light-gauge steel C-sections used instead of timber, common in flats and commercial conversions. A magnet finds them instantly, and they take self-drilling fixings rather than woodscrews.

Can I hang anything heavy on a stud wall?

Yes, if the load goes into the studs. Fixings into the board alone, however clever, have modest limits and are unsuitable for anything that would hurt someone if it fell.