Screws, wall plugs and fixings: start with the wall

Find out what you are fixing into

A painted wall does not tell you much about what is behind it. It might cover plaster on masonry, plasterboard on framing, or a different construction altogether. The surface finish and the material that must carry the load are not necessarily the same thing.

Masonry includes materials such as brick, stone and concrete blocks, but those are not interchangeable substrates for every fixing. Plasterboard is a gypsum-based sheet material and calls for an appropriate fixing or suitable structural backing. If you cannot establish the wall construction, get advice before deciding on a fixing.

What a wall plug actually does

A wall plug goes into a suitable drilled hole and helps provide grip for a screw. “Rawlplug” is a brand name often used casually to mean a plastic wall plug. Neither name tells you which substrate, screw size or load a particular product is designed for.

Choose the exact plug or anchor from its manufacturer’s guidance for the identified material and application. Follow the stated screw requirements and installation instructions. Picking a familiar colour from a mixed box is not a substitute for knowing the product.

Hollow walls need their own approach

Some hollow-wall fixings use a mechanism behind the board. A toggle fixing, for example, has a folding or expanding element that provides support behind a sheet. Whether it is suitable depends on the specific fixing and the construction, including the available space.

Do not assume that all plasterboard fixings carry the same load, or that adding more of them automatically makes an unsuitable arrangement safe. Shelves, cabinets and items pulled away from the wall place different demands on their fixings. Heavy, overhead or safety-critical installations deserve professional assessment.

Choose the screw as part of the fixing system

The screw needs to suit the fixing, the object and the environment. Head shape, dimensions and material protection all matter. A countersink is a cone-shaped recess that lets an appropriate screw head sit flush with or below a surface; it is not a reason to modify every item you attach.

A pilot hole is a small hole made to guide a screw and help reduce splitting in suitable materials. Its requirements depend on the screw and task. Likewise, zinc plating offers a degree of corrosion protection, but the exact coating and exposure determine where a screw is suitable. Do not assume a shiny finish proves outdoor suitability.

Use rated information, not guesswork

Check the fixing manufacturer’s stated capacities and the conditions attached to them. A load figure is only useful when it applies to the actual substrate, installation and loading arrangement. This guide gives no universal weight limits because there is no one number that covers every wall.

Before drilling, investigate hidden electrical cables, pipes and other services using appropriate information and checks. Follow the product instructions, and stop if the wall or hole is not what you expected. Do not rely on a fixing to compensate for damaged or unsuitable backing material.

For a buying list, record the object, wall construction, fixing reference and specified screw. That is more useful than asking for “some plugs and screws” and hoping the pieces work together.

The takeaway

• Identify the material carrying the load before choosing a fixing.
• Use the specified screw and installation guidance for the exact fixing.
• Ask for qualified advice where the construction or loading is uncertain.