The basic difference between plastering and rendering is that plastering is carried out on interior surfaces while rendering is undertaken on exterior surfaces. More specifically, the difference between plastering and rendering concerns the combination and type of materials used.
Why Different Materials?
The composition of the plaster depends on whether it is being applied on an exterior or exterior surface (for the most part). If exterior, then durability and weather proofing is the main consideration so the composition of the plaster will reflect this. The plaster for exterior use will contain more cement than for interior surfaces, and while this makes the plaster coarser than the smoother-finish interior plaster, it makes the plaster (‘render’) more durable.
By using less cement in the mixture for interiors, it makes the plaster smoother and more appealing-looking and far easier to paint.
Whether for rendering or plastering, the basic composition of the mortar is broadly similar – cement, sand, water and sometimes lime. For rendering, as well as a higher proportion of cement a coarser type of sand is preferred whereas for plaster finer sand is used in the interests of a smoother finish.
The composition of render and plaster is flexible depending on the exact circumstances. For example, exterior surfaces bearing the brunt of the severest weathering (in line with the prevailing winds) would have a richer mixture (more cement) than the more sheltered walls. Similarly, an interior surface subject to wetter conditions – such as a bathroom – would have a richer mixture than other interior surfaces.
Another consideration is cracking. The richer the mixture, the more surfaces are subject to cracking – this is why amounts of cement are varied according to specific surface requirements. For example, were it not for cracking one might simply render the entire exterior of a property with the same rich mixture as used for the more weathered surfaces.
Acrylic and Premixed Rendering
There are a wide variety of premixed renders for different applications, some have additives – such as polymer – for enhanced water resistance and adhesion. Acrylic premixed renders offer enhanced water resistance and strength, and can be used on a huge variety of surfaces including smoother ones such as cement sheeting.
Some of these acrylic renders offer a smoother finish than traditional renders, and can even be sprayed on. Various finishes are possible such as sandstone, stone or marble effect, and acrylic renders dry far quicker than the traditional render.
Modern techniques and skills mean different types of finish are achievable for both plastering and rendering. Although rendering gives a broadly coarser finish than plastering, it is possible to vary these with the use of sponges, trowels or brushes. Pebble dashing is a type of rendering.
Sometimes a ‘render’ may be used on interior surfaces in the interests of aesthetics. Sometimes a coarse, rough finish to a surface is desired and rendering is the best way to achieve this.
If you think you may need plastering or rendering done to your home contact us directly at Telephone Number 020 8854 1025 or via e-mail in the box below.