What size and type of shelf bracket do I need?

Brackets are usually chosen on looks and price, and the two dimensions that actually decide whether the shelf works get ignored. Both are geometry rather than strength, which is why the load rating on the packet tells you so little.

Step by step

1. Measure the shelf depth first.The bracket is chosen to suit the shelf, not the other way round. A 300mm deep shelf needs an arm of at least 200mm.
2. Apply the two-thirds rule to the arm.Arm length at least two thirds of the shelf depth, ideally three quarters. The remaining front overhang should be no more than about 50mm, because the board bends over the tip of the arm and anything placed beyond it acts on a lever.
3. Take the tallest upstand available.The vertical part against the wall. The pull-out force on the top screw is inversely proportional to the distance between the two screws, so a bracket with 150mm between its holes puts roughly half the force on the top fixing that a 75mm one does. This is the single most overlooked bracket decision.
4. Count the fixing holes and use all of them.Manufacturers do not add holes for decoration. Three holes means three screws.
5. Choose the type against the job.Pressed steel angle brackets are cheap and adequate for light shelves. Cast or heavy pressed brackets with a gusset or a diagonal web are the real answer for books. Twin-slot systems are the right choice for a multi-shelf run that may need adjusting. Concealed or floating fittings suit light display shelves only.
6. Check the bracket sits against the wall, not the skirting or a bead.A bracket bridging a corner bead or resting on a curved plaster edge is only touching at one point, which turns the whole load into a prying action.
7. Match the screw to the bracket hole, then to the wall.The hole size in the bracket sets the maximum screw shank. Countersunk heads for countersunk holes; a pan head on a countersunk hole sits proud and stops the shelf sitting flat.
8. Plan the bracket positions around the studs on a hollow wall.Brackets should land on studs. Where they cannot, screw a timber batten horizontally across two or more studs and fix the brackets to the batten.
9. Fix the shelf down to the brackets.Most brackets have small holes in the top face for short screws up into the shelf. They stop the board sliding or lifting and cost nothing to use.

Tips

• For a shelf people will put things on, screw the board down to the brackets. For a shelf children can reach, treat that as mandatory.
• A bracket with a diagonal web under the arm is far stiffer than a plain L, and usually only slightly dearer.
• If the bracket you want is too short in the arm, a deeper shelf is not the answer — a shallower shelf is.

Common mistakes

• Buying brackets that match the shelf depth exactly — They usually do not exist in that size, and people then buy short. Buy for two thirds of the depth as a minimum and accept a small front overhang.
• Choosing a small neat bracket for a heavy shelf — The short upstand puts the two screws close together, which multiplies the outward force on the top screw. It is the geometry, not the steel, that fails.
• Ignoring the third fixing hole — The load is shared between the fixings that exist. Two out of three means each of them works half again as hard.

If it doesn't work

Questions people ask