What Plaster, Drywall & Interior Finishing covers
This section covers interior finishing materials: cement plaster, skim plaster, gypsum products, plaster primers and the drywall systems used for internal partitions.
Two terms cause most of the confusion, and one of them is distinctly South African. Rhinolite is a gypsum skim plaster that has become the generic name here for the smooth white finish applied over cement plaster or board — much as people say “Jeyes fluid” or “Cellotape”. It is a finishing layer, typically a few millimetres thick, and it is not a substitute for the cement plaster underneath.
Plaster of Paris is a different product entirely, despite the shared word. It sets very quickly, is used for casts, mouldings and small repairs, and is not a wall finish. People buy it expecting a skim coat and find it has gone hard in the bucket before they reach the wall.
The plaster key is the third thing worth understanding, and it explains most plaster failures. A key is the mechanical grip the plaster gets on the surface behind it — a scratched undercoat, a scored surface, or the roughness of blockwork. Plaster applied to something smooth and unkeyed, or to a dusty or overly absorbent surface, falls off in sheets later. That is what a plaster primer is for: it controls suction and improves adhesion.
Browse individual used-for guides
- Blue Plasterboard used for
- Bonding Plaster used for
- Explain What Plaster Of Paris used for
- Gypsum used for
- One Coat Plaster used for
- Plaster Bonding used for
- Plaster Key used for
- Plaster Mix used for
- Plaster Of Paris used for
- Plaster Primer used for
- Plaster used for
- Plasterboard used for
- Rhinolite used for
- Tools used for
- What Size Drywall used for
- Which Sand used for
- Zinc Oxide Plaster used for
Most searched questions in this topic
- Rhinolite used for
- Plaster Key used for
- Gypsum used for
- Plaster Primer used for
- Plaster Of Paris used for
- Explain What Plaster Of Paris used for
- Plaster used for
- Tools used for
How the guides in this section differ
Base coat or finish coat. Cement plaster is the base that builds and levels. Skim plaster is the thin finish that produces a paintable surface. They are not interchangeable in either direction.
Gypsum or cement. Gypsum products give a smooth interior finish but are not suitable for permanently damp or external conditions. Cement-based plaster handles moisture and exterior exposure.
Wet plaster or drywall. Traditional plaster is applied wet over masonry. Drywall is board fixed to a frame with jointed seams — faster, drier, lighter, and hollow, which matters for fixing things to it.
Repair or finish. Plaster of Paris and fillers are for repairs and mouldings. Skim plaster is for finishing areas.
| Product | Job | Typical mistake |
|---|---|---|
| Cement plaster | Base coat over masonry, levels the wall | Applied too thick in one pass |
| Skim plaster (Rhinolite) | Smooth finish coat before painting | Used as a base coat or over an unprimed surface |
| Plaster of Paris | Casts, mouldings, small repairs | Bought expecting a wall skim |
| Plaster primer | Controls suction, aids adhesion | Skipped on porous or smooth surfaces |
| Gypsum board (drywall) | Partitions and ceilings on a frame | Fixing heavy items without a proper anchor |
Related topics and alternatives
- Explore Paints, Primers, Coatings & Waterproofing
- Explore Timber, Boards & Woodworking Materials
- Explore Structural & Masonry Materials
Safety, accuracy and next-step checks
These guides explain what materials are for and follow manufacturer technical data.
Points worth carrying:
- Sanding plaster and joint compound creates fine dust. Use extraction or damp-sand, ventilate, and wear a properly rated mask. It travels through a house readily.
- Prepare and prime the surface. Suction control is the difference between plaster that bonds and plaster that debonds. Dusty, smooth or highly absorbent surfaces need a primer.
- Do not skim over damp. Damp will push the finish off and reappear as staining. Find and fix the water source first.
- Respect drying and curing times between coats. Rushing traps moisture and causes cracking and poor adhesion.
- Fix properly into drywall. Board alone will not hold weight. Use cavity anchors, or fix into the studs behind — mirrors, televisions and cabinets pulling out of drywall is a common and avoidable failure.
- Wet gypsum should be replaced, not dried. Board that has been soaked loses strength and may harbour mould.
- Wear gloves and eye protection. Cement-based products are alkaline and burn skin; plaster in the eye needs immediate irrigation and medical attention.
- Ceilings need care. Overhead work risks falling material and is where most DIY plastering injuries happen.
Frequently asked questions
What is Rhinolite used for? It is a gypsum skim plaster applied as a thin smooth finish over cement plaster or board, ready for painting. The name is used generically in South Africa.
Is plaster of Paris the same as skim plaster? No. Plaster of Paris sets very quickly and is for casts, mouldings and small repairs. It is not a wall finish.
What does a plaster primer do? It controls how much water the surface draws out of the plaster and improves adhesion. On porous or smooth surfaces it is what keeps the plaster attached.
Can I plaster straight onto smooth concrete? Not without preparation. Smooth surfaces give no key, so a bonding agent or scored key coat is needed first.
Why is my plaster cracking? Common causes are applying too thick in one pass, drying too fast, movement in the substrate, or missing preparation. Fine crazing differs from structural cracking, and widening cracks warrant investigation.