Question 1

1. What’s the difference between rendering and plastering?

Accepted Answer

Rendering and plastering both involve applying a layer of wet material (plaster or render) to a substrate like brick or plasterboard, which hardens to form a protective coating. The big difference is that plastering is done on interior walls and ceilings, and rendering is done to exterior walls.

Plastering and rendering also use different materials. Plastering is usually done with gypsum plaster, while rendering is traditionally done with a concrete render mix (although types of render made of synthetic materials like silicone are becoming more popular).

Question 2

2. What is render / what is rendering?

Accepted Answer

Render is a protective layer that’s applied to exterior walls. It’s usually made up of cement, plastering sand, and water, although additional materials like lime or admixtures are sometimes added too. Rendering is the process of applying it to the wall, usually to protect it from the weather (although it can also be used to make it look better).

Types of rendering materials include:

Silicone render – Highly water-repellent, breathable, and self-cleaning.
Monocouche render – Pre-coloured, single-coat render for a fast, decorative finish.
Acrylic render – Flexible and decorative, applied as a topcoat.
Lime render – Breathable and ideal for older or heritage buildings.

Question 3

3. What is plaster?

Accepted Answer

When we talk about plaster, we’re usually talking about gypsum plaster (also known as plaster of Paris). It’s usually used for plastering internal walls to create a smooth, even surface for decorating. Plaster is generally applied in a thinner coat than render, especially when it’s being used for ‘skimming’ (applying a thin, smooth layer of finishing plaster). Other types of plastering materials include cement plaster, lime plaster and clay plaster mixes, although these are less common.

Question 4

4. What sorts of additives and admixtures are available for plaster and render?

Accepted Answer

Additives and admixtures can improve workability, setting time, strength, and water resistance. Common options include:

Plasticisers - to improve workability
Retarders - to slow down setting time for longer working periods
Accelerators – to speed up setting for faster application
Waterproofers – to help the finished surface resist moisture
Bonding agents – to improve adhesion to surfaces
Fibres – to reduce cracking and improve the tensile strength of the surface
Lime – adds flexibility and helps prevent shrinkage

Plaster and render supplies

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