What this advisor works out
This advisor suggests a fixing type based on the wall construction, the weight of what you are hanging and whether the location is indoor or damp.
It gives a starting point. The binding figure is always the safe working load published by the fixing manufacturer for that specific product in that specific material, and that varies more than most people expect.
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Before you fix anything
- Identify the wall correctly. Dot and dab plasterboard looks like plasterboard and behaves like neither — there is a cavity of 10 to 25 mm between the board and the masonry behind.
- Use the loaded weight, not the empty weight. A bookshelf full of books is many times the weight of the shelf.
- Consider leverage. A deep shelf or a bracket that holds the load away from the wall multiplies the pull-out force at the top fixings.
- Check for cables and pipes before drilling, every time.
A fixing carrying a shelf is mostly in shear, loaded downwards along the wall. A fixing holding a wall-mounted TV bracket, or the top screws of a deep shelf, are in tension and being pulled straight out. Pull-out is the weaker direction for almost every fixing, and manufacturers publish separate figures for each.
How this calculator works
A recommendation by wall type and weight band:
Plasterboard: up to 5 kg self-drill fixing · to 20 kg metal cavity anchor · above that, fix to studs
Brick or block: to 15 kg 6–7 mm plug · to 50 kg 8–10 mm plug or frame fixing · above that, heavy duty or resin anchor
Timber stud: fix directly into the stud
Dot and dab: long plug reaching the masonry behind, or a resin fixing
Tiled: tile bit through the tile, then the fixing for the wall behindOutdoor or damp locations add a recommendation for corrosion-resistant fixings. Stainless steel or properly coated fixings matter more than most people assume — ordinary zinc-plated screws in a damp wall can fail within a few years.
Anything above 30 kg is flagged as a high load. That is not a limit, but it is the point at which reading the manufacturer's data becomes essential rather than advisable.
Worked example: 10 kg on plasterboard
Using the default figures — a hollow plasterboard wall, 10 kg, indoors:
- Suggested fixing: metal cavity anchor fitted with a setting tool
- Risk level: normal DIY check
Worth noting what this assumes: that the 10 kg hangs close to the wall. Put the same 10 kg on a 300 mm deep shelf and the top fixings are being levered outwards with considerably more force than 10 kg. If a timber stud is anywhere near, fixing into it is always better than any cavity anchor — a screw into solid timber outperforms every hollow-wall fixing made.
Common mistakes
- Using the empty weight. Loaded weight is what the fixing carries.
- Treating dot and dab as solid masonry. A short plug bridges nothing and pulls out with the plasterboard.
- Ignoring leverage on deep shelves and brackets. Pull-out force can far exceed the weight.
- Using indoor fixings outdoors. Corrosion causes failures years later.
- Relying on a single fixing. Spreading load across several is far more forgiving.
Frequently asked questions
How do I find a timber stud?
An electronic stud detector is the usual method, calibrated on a known hollow section first. Studs are commonly at 400 or 600 mm centres, so finding one lets you predict the others. Tapping works with practice. A small pilot hole through the plasterboard confirms it — wood shavings mean a stud, dust and then nothing means a cavity.
What is dot and dab and why does it matter?
It is plasterboard stuck to masonry on dabs of adhesive, leaving an air gap of 10 to 25 mm. It looks and sounds like plasterboard but a cavity fixing has nothing to grip, and a standard plug is too short to reach the masonry. You need a plug long enough to pass through the board and the gap and anchor in the wall behind — often 80 mm or more.
Can I hang a TV on a plasterboard wall?
Onto plasterboard alone, no. A television bracket applies substantial leverage and needs fixing into studs, into the masonry behind dot and dab, or onto a plywood pattress spanning at least two studs. This is the single most common cause of failed wall fixings, and the failure is expensive.
What does safe working load mean?
The load a fixing is rated to carry in a stated material, with a safety factor already applied against ultimate failure. It is specific to the material — the same anchor has very different figures in concrete, in solid brick and in aerated block. Manufacturer datasheets give the figures; general guidance cannot.
Is what I enter stored?
No. Weights and wall types are processed in your browser and never transmitted or retained.
Related tools
References
- Health and Safety Executive — safe working practice, buried services and power tool use
- GOV.UK — building regulations guidance relevant to fixings and structure
Sources are checked at publication and can change — how I choose and check references.