“What Type of Wall Do I Have?” A Step-By-Step Guide to Wall Materials
A quick guide to stud walls, dot and dab, and solid masonry
Before you even think about which fixing to buy, you need to figure out a more basic question: What’s your wall actually made of? This isn’t something to mess about with or ignore, as even the right fixing, fitted correctly, can fail. But if you get the wall material right, the rest of the job gets (thankfully) a lot easier.
Most DIYers only ask this question halfway through drilling a hole, when the drill bit suddenly plunges through empty space or grinds to a halt on something solid. This guide is here so you can answer it first, before a single hole goes in the wall.
Quick Answer: Basically, three wall types cover most UK homes.
Stud walls are timber or metal frames with plasterboard fixed directly to them. They’re hollow throughout, except where a stud sits behind the board.
Dot and dab walls are plasterboard fixed to solid masonry using blobs (“dabs”) of adhesive. There’s an air gap behind the board, and its depth varies from wall to wall and even from spot to spot on the same wall.
Solid masonry is brick or block with a layer of plaster skimmed straight onto it. No plasterboard and no cavity.
Each of these needs a different fixing approach though, which is exactly why working out which you’ve got is worth five minutes before you go ahead and drill.
The knock test
The simplest way to start is to tap the wall with your knuckle and listen. A dull, deep, solid thud usually means solid masonry, or a stud, or the dabs of a dot and dab wall. A hollow, higher-pitched sound usually means an air gap behind the plasterboard, which points to a stud wall or the gaps between the dabs on a dot and dab wall.
You’ll want to work your way across the wall in a grid, tapping every 20 to 30cm or so, and pay attention to how the sound changes. On a stud wall, you’ll get mostly hollow sound punctuated by solid thuds roughly every 400 to 600mm, where the studs are. That regular, evenly spaced pattern is the giveaway.
This is where dot and dab walls can trip people up. The adhesive is applied in blobs, not a continuous layer, so a dot and dab wall gives you a patchwork of solid and hollow sounds with no obvious pattern or spacing. One tap sounds solid because you’ve hit a dab, the next sounds hollow because you’ve hit the gap between dabs, and there’s no regular rhythm to it the way there is with studs. If the sound changes constantly and randomly as you move across the wall, dot and dab is the most likely explanation.
Quick summary of what dot and dab actually is, for anyone new to the term: it’s plasterboard fixed to solid masonry with adhesive applied in blobs rather than a full bed of plaster or a timber frame, which leaves a gap of anywhere from a few millimetres to 50mm or more behind the board. We’ve gone into dot and dab in a lot more depth in our other guides, including what dot & dab walls are, the difference between dot and dab and a stud wall, and why standard wall plugs fail in dot & dab walls.
Using a stud or cavity detector, or the magnet trick
A stud and cavity detector is a bit more precise than the knock test, and worth having on hand if you do a lot of DIY. If you run it slowly across the wall, it’ll flag changes in density, hollow sections, and in some cases the metal fixings holding the board in place. They’re inexpensive, and worth keeping in the toolbox if you’re doing much fixing work at all.
If you don’t have one to hand, there’s a low-tech trick that comes up again and again in DIY forums, and it actually works: the magnet method. Plasterboard is fixed to studs with metal screws or nails, and a strong magnet (a fridge magnet is usually too weak, but a small neodymium magnet works well) will find them. You can just run the magnet slowly over the wall in a grid pattern, the same way as the knock test, feeling for where it pulls or clicks against the surface. So finding a screw head means there’s a fixing point underneath, most likely a stud or a noggin, and finding two or three in a vertical line gives you a strong clue to where the timber runs.
This trick won’t tell you much about the depth of the cavity behind, though. Knowing the cavity depth is important for plasterboard cavity wall fixings and dot & dab fixings, as you need to check if the fixings are able to open fully inside the cavity or reach far enough in to grip the blockwork. For that, you’ll need one of the methods below.
Checking from an unseen angle
If you can get a direct look at the wall’s construction somewhere it doesn’t matter so much, it’s worth doing. This is the most reliable method of all because you’re not interpreting sound or feel, you’re actually seeing what’s there.
A loft space is often the best place to start. Where a wall continues up into the loft, you can usually see if it’s a timber frame or blockwork, and get a rough sense of the thickness. Other places you might be able to get the same view are airing cupboards, understairs cupboards, or any other unfinished or rarely seen area of the house.
Existing holes are also another good option. If you’re near a socket, light switch, or any other cut-out in the wall, you can often see the wall’s construction by easing the socket out of the wall.
A word of caution here though – you should NEVER poke around inside a socket or switch, or remove its faceplate, without turning off the power at the consumer unit first! If you’re not confident isolating a circuit safely, then this step isn’t worth the risk and the other methods in this guide will get you most of the way to an answer anyway.
Drilling a pilot hole
If the knock test, magnet, and any visual check are still leaving you unsure, drilling a small pilot hole in an inconspicuous spot is a handy way to settle it for good – a 3 to 4mm bit is usually enough. Just drill slowly and stop the moment you feel a change in resistance. You’ll be able to tell fairly quickly what you’ve found: solid material straight away, empty space followed by something solid a little further in (a strong sign of dot and dab), or emptiness all the way through other than a stud (a stud wall).
It’s worth choosing the location carefully though – somewhere that will be covered by furniture, a picture, or the fixing you’re about to install is perfect.
Before you drill anywhere, you should check for pipes and cables! This matters on every wall type and it’s easy to forget when you’re focused on working out the wall material and construction. UK wiring practice generally keeps cables within defined “zones”, most commonly running vertically or horizontally in a line from a socket or switch, or within about 150mm of the top of a wall, a ceiling line, or a corner. Drilling well away from these zones (and away from sockets, switches, and light fittings generally) reduces the risk by a lot, though remember that not every installation follows the guidance to the letter. Plumbing tends to cluster near kitchens, bathrooms, and anywhere with a boiler or radiator, and pipework often runs vertically up from the floor or horizontally just above skirting board height. If you’re going to be drilling into walls more than once or twice, then a cable and pipe detector is a sound investment and earns its keep even when you’re fairly confident about where services are likely to be.
What each wall type means for your fixing choice
Once you know what you’re dealing with, the right fixing becomes a much easier decision.
| Wall type | What it means | Fixing to use |
|---|---|---|
| Stud wall | Hollow with timber or metal studs at intervals | Fix directly into a stud where possible, or use a hollow-wall toggle fixing that spreads the load across the plasterboard itself |
| Dot and dab | Plasterboard with an air gap over solid masonry | A fixing that bridges the gap and transfers load to the masonry behind, such as Corefix Connect |
| Solid masonry | Brick or block with a plaster skim, no cavity | A standard wall plug and screw sized correctly for the hole and the load |
| Hollow block | Blockwork with internal cavities | An adjustable toggle fixing designed for hollow materials, such as Corefix Strap or a spring toggle |
| Aerated concrete (e.g. Thermalite or similar) | A lightweight, crumbly block material | Treat it broadly like solid masonry, but drill with care. Use a smaller drill bit for a tighter fit and turn off the hammer function to avoid crumbling the material around the hole |
For a general-purpose option that copes with medium duty loads in more than one wall type, Corefix One is designed to work across a range of materials. And that’s useful if you’re still not entirely sure what you’re dealing with.
Still not sure? If you get it wrong…
Misidentifying the wall type is one of the most common reasons a heavy fixing fails, often more so than a poor-quality fixing or plain bad luck. It’s simply the wrong fixing for the wall material.
Most of the time, that’s a minor inconvenience. A shelf comes away from the wall, you patch the hole, you try again. (For tips on how to fix common DIY fails, check out this guide.) But if the job involves real weight, expense, or risk, like a radiator, a boiler, a TV bracket, or a wall-mounted cupboard full of crockery, then it’s better to aim for certainty rather than confidence. If you’ve worked through the checks in this guide and you’re still not sure what’s behind your wall, you should take the extra five minutes to check again, or ask a professional tradie to confirm it.
If you already know you’re dealing with a dot and dab wall and a heavy item like a TV, radiator or boiler, our TV mounting guide and Boiler Fixing Guide cover exactly how to fix them properly.
How can I tell if a wall is stud, dot and dab, or solid masonry?
Tap it with your knuckle and listen. A dull, deep, solid thud usually means solid masonry, a stud, or the dabs of a dot and dab wall. A hollow, higher-pitched sound usually means an air gap behind the plasterboard, pointing to a stud wall or the gaps between the dabs on a dot and dab wall.
You'll want to work your way across the wall in a grid, tapping every 20 to 30cm or so, and pay attention to how the sound changes. On a stud wall, you'll get mostly hollow sound punctuated by solid thuds roughly every 400 to 600mm, where the studs are. That regular, evenly spaced pattern is the giveaway.
This is where dot and dab walls trip people up, though. The adhesive is applied in blobs, not a continuous layer, so a dot and dab wall gives you a patchwork of solid and hollow sounds with no obvious pattern or spacing. One tap sounds solid because you've hit a dab, the next sounds hollow because you've hit the gap between dabs, and there's no regular rhythm to it the way there is with studs. If the sound changes constantly and randomly as you move across the wall, dot and dab is the most likely explanation.
What is a dot and dab wall?
A dot and dab wall is plasterboard fixed to solid masonry with adhesive applied in blobs (the "dots and dabs") rather than a full bed of plaster or a timber frame. This leaves a gap of anywhere from a few millimetres to 50mm or more behind the board. We've gone into dot and dab in a lot more depth in our other guides, including what dot & dab walls are, the difference between dot and dab and a stud wall, and why standard wall plugs fail in dot & dab walls.
How do I use a stud detector or a magnet to find a stud?
A stud and cavity detector makes the knock test far easier to read. Run it slowly across the wall and it'll flag changes in density, hollow sections, and in some cases the metal fixings holding the board in place. They're inexpensive, and worth keeping in the toolbox if you're doing much fixing work at all.
If you don't have one to hand, there's a low-tech trick that comes up again and again in DIY forums, and it actually works: the magnet method. Plasterboard is fixed to studs and to some dot and dab dabs with metal screws or nails, and a strong magnet (a fridge magnet is usually too weak, but a small neodymium magnet works well) will find them. You can run the magnet slowly over the wall in a grid pattern, the same way as the knock test, feeling for where it pulls or clicks against the surface. A screw head means there's a fixing point underneath, most likely a stud or a noggin, and finding two or three in a vertical line gives you a strong clue to where the timber runs.
This trick works on dot and dab walls too, since the board is still screwed to the dabs, but it won't tell you much about the depth of the cavity behind.
How can I check my wall type without drilling?
If you can get a direct look at the wall's construction somewhere it doesn't matter, it's worth doing. This is the most reliable method of all, because you're not interpreting sound or feel, you're actually seeing what's there.
A loft space is often the best place to start. Where a wall continues up into the loft, you can usually see if it's a timber frame or blockwork, and get a rough sense of thickness. An airing cupboard, understairs cupboard, or any other unfinished or rarely seen area of the house can offer the same view.
Existing holes are another good option. If you're near a socket, light switch, or any other cut-out in the wall, you can often see the wall's construction by easing the socket out of the wall. A word of caution though – you should NEVER poke around inside a socket or switch, or remove its faceplate, without turning off the power at the consumer unit first! If you're not confident isolating a circuit safely, then this step isn't worth the risk.
Is it safe to look inside a socket or light switch to check my wall cavity depth?
Only with the power off. Never poke around inside a socket or switch, or remove its faceplate, without turning off the power at the consumer unit first. If you're not confident isolating a circuit safely, then it isn't worth the risk. If in doubt, an electrician can check this for you in a few minutes.
How do I drill a test hole to check what's behind my wall?
Drilling a small pilot hole in an inconspicuous spot is a godo way to find out what your wall is made of and what's behind it (cavity or masonry for example). A 3 to 4mm bit is enough. Just drill slowly, and stop the moment you feel a change in resistance. You'll be able to tell fairly quickly what you've found: solid material straight away, empty space followed by something solid a little further in (a strong sign of dot and dab), or emptiness all the way through other than a stud (a stud wall).
It's worth choosing the location carefully. Somewhere that will be covered by furniture, a picture, or the fixing you're about to install is ideal.
Where are pipes and cables usually located in a UK wall?
Before you drill anywhere, you should check for pipes and cables, on every wall type. UK wiring practice generally keeps cables within defined "zones", most commonly running vertically or horizontally in a line from a socket or switch, or within about 150mm of the top of a wall, a ceiling line, or a corner (per BS 7671 guidance on permitted cable zones). Drilling well away from these zones, and away from sockets, switches, and light fittings generally, reduces the risk considerably, though it's not a guarantee, since not every installation follows the guidance to the letter. Plumbing tends to cluster near kitchens, bathrooms, and anywhere with a boiler or radiator, and pipework often runs vertically up from the floor or horizontally just above skirting board height. A cable and pipe detector is a sound investment if you're going to be drilling into walls more than once or twice, and it earns its keep even when you're fairly confident about where services are likely to be.
What fixing do I need for each wall type?
Stud walls: Fix directly into a stud where possible, or use a hollow-wall toggle fixing that spreads the load across the plasterboard itself.
Dot and dab: A fixing that bridges the gap and transfers load to the masonry behind, such as Corefix Connect.
Solid masonry: A standard wall plug and screw sized correctly for the hole and the load.
Hollow block: An adjustable toggle fixing designed for hollow materials, such as Corefix Strap or a spring toggle
Aerated concrete (like Thermalite or similar): Treat it broadly like solid masonry, but drill with care. Use a smaller drill bit for a tighter fit and turn off the hammer function to avoid crumbling the material around the hole.
What happens if I use the wrong fixing for my wall type?
Misidentifying the wall type is one of the most common reasons a heavy fixing fails, often more so than a poor-quality fixing or plain bad luck. It's simply the wrong fixing for what's actually behind the plaster.
Most of the time, that's a minor inconvenience. A shelf comes away from the wall, you patch the hole, you try again. But if the job involves real weight or genuine risk, a radiator, a boiler, a TV bracket, a wall-mounted cupboard full of crockery, it's better to aim for certainty rather than confidence. If you're still not sure what's behind your wall, you should take the extra five minutes to check again, or ask a tradesperson to confirm it.