What this category covers

This section explains what construction and building materials are used for: cement and concrete, timber and boards, paints and primers, plaster and drywall, adhesives, sealants and grouts, roofing and insulation.

The guides are written for the person standing in a builders’ merchant deciding between two products, or trying to work out whether the material already on site is the right one for the job. Each answers the direct question — what is this for — and then covers the part that actually causes problems: where a material is appropriate, what it is compatible with, and where it will fail.

Choosing the wrong material rarely shows up immediately. Using an interior filler outside, a general-purpose adhesive on a wet wall, or the wrong sand in a mix produces work that looks fine and fails months later. These guides try to flag those cases before you buy.

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How to choose the right guide

Start from the material name printed on the bag, tin or label. South African merchants stock several products under names that have become generic here — Rhinolite for skim plaster is a good example — and the guides use the names you will actually be given at the counter.

If you know the job but not the material, work down from the topic list instead. That path matters most for adhesives, sealants and coatings, where products look interchangeable and are not: an interior grout and an exterior grout, or a general-purpose silicone and a sanitary-grade one, do different jobs.

When two products seem to overlap, check what the guide says about the substrate and the conditions. Substrate, moisture and movement decide most material choices, far more than brand.

Safety, accuracy and South African context

Building materials carry real hazards, and the common ones are chemical and respiratory rather than dramatic.

On anything structural, these guides are informational only. Load-bearing walls, beams, foundations, roof structures and retaining walls need a qualified engineer or builder, and the guides say so rather than offering a rule of thumb. South African work is also subject to the National Building Regulations and to municipal approval for many alterations — worth confirming before work starts, not after.

Where a guide makes a technical claim, it follows manufacturer specifications and technical data sheets. Where the manufacturer’s spec differs from a general rule, the spec wins.

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Frequently asked questions

Is cement the same as concrete? No. Cement is the binder. Concrete is cement mixed with sand, stone and water. Mortar is cement, sand and water without stone. Asking for the wrong one is a common counter mix-up.

Do I really need a primer? Usually yes, on bare, porous, chalky or previously unpainted surfaces. Primer is what gives the topcoat something to bond to, and skipping it is the usual reason paint peels.

Can I use interior products outside? No. Exterior products are formulated for UV, moisture and temperature movement. Interior fillers, adhesives and paints fail outdoors, sometimes within a season.

Is silicone suitable everywhere? No. Standard silicone is not paintable, and general-purpose grades are not suitable in bathrooms where a sanitary grade with mould resistance is needed. Check the tube.

Do these guides cover structural decisions? No. They explain what materials are for. Anything load-bearing needs a qualified professional and, in most cases, municipal approval.