Reference

How to identify your wall type (before you fix shelves to it)

How you fix a shelf to a wall, and how much it can safely hold, depends entirely on what the wall is made of. A screw into solid timber or brick holds far more than one into a thin plasterboard skin. Before you build a fitted or wall-fixed unit, find out which of three walls you have. It takes two minutes and it changes the fixings you buy and the load the shelf can carry.

Solid masonry wall (brick or block)

What it is: solid brick, concrete block, or stone, usually plastered over. Common in older homes, external walls, and ground floors.

How to tell:

• Knock on it: a solid, dull sound with no echo. It feels hard and does not flex.
• Drill a test hole: red or brown dust means brick; grey dust means concrete block.
• A magnet finds nothing regular behind the surface (there are no studs).

How you fix into it: drill with a masonry bit (a hammer drill helps), push in a wall plug, then drive the screw. This is a strong fixing.

In Kamba: choose "Brick or block".

Stud wall (timber frame behind plasterboard)

What it is: a hollow wall built from vertical timber studs, usually spaced about 40 to 60 cm apart (16 inches in the US), covered with a plasterboard skin. Common in modern homes, internal partitions, and upper floors.

The key point: you want to fix into the studs (the timber), not into the board between them. A screw into a stud is strong; a screw into the board alone is weak and can pull out.

How to find the studs:

• A stud finder (inexpensive) beeps as it passes over a stud.
• Tap along the wall: over a stud the sound is solid; between studs it is hollow.
• A strong magnet catches on the screws that hold the board to each stud, revealing a vertical line.
• Studs usually sit about 40 to 60 cm apart, and there is almost always one beside each window and door frame.

How you fix into it: drive the screw straight into the stud, with no wall plug. This is the strongest fixing you can make in a hollow wall.

In Kamba: choose "Stud wall". Your plan fixes into the timber studs.

Plasterboard (fixing into the board only)

What it is: the plasterboard skin of a hollow wall, at a point where your fixing does not land on a stud. The board is only about 9.5 to 15 mm thick.

How to tell: it sounds hollow when knocked, flexes slightly under pressure, and gives off white, chalky dust when drilled, with no timber behind at that point.

How you fix into it: an ordinary screw will pull straight out, so you need a proper cavity fixing (a spring toggle or a heavy-duty plasterboard anchor) rated for the weight. Even then, plasterboard holds far less than a stud or masonry, and thinner board holds less again.

Best practice: wherever you can, move the fixing sideways to land on a stud instead. It is always stronger.

In Kamba: choose "Plasterboard". Because this is the weakest case, the plan bounds the safe load low, asks how thick your board is, and asks you to have the wall confirmed before you load it.

Quick tests at a glance

• Knock: a solid, dull sound means masonry; a hollow sound means a stud wall or plasterboard.
• Magnet: it catches along regular vertical lines when there are studs behind; it finds nothing on solid masonry.
• Drill dust: red or brown means brick, grey means block or concrete, white and chalky means plaster or plasterboard.
• Stud finder: it signals when it passes over a stud.

Not sure?

If you cannot tell for certain, pick the most conservative option (Plasterboard). Kamba then assumes the weakest wall and keeps the safe load low. And if a wall is carrying real weight and you are not confident about it, have a builder confirm the fixing before you load the shelves. There is no downside to being careful here.

Next: once you know your wall, see how to anchor a unit against tipping

See also: shelving hardware and conversions

Read the full guide: how to build custom shelving

See all guides and references