External rendering in Guildford is a similar process to plastering except that it is carried out on the external walls of a building, largely with the object of improving the appearance of walls which have become shabby with age. Many new build homes also have the walls rendered in a chosen colour, and render is very common around the Mediterranean where you see whole towns with homes of white walls.

Rendering a wall also helps with waterproofing it and to some extent fireproofing. While many homeowners choose to have a smooth finish to the render, it can also have one of any number of decorative finishes. Different textured finishes can be achieved by using a trowel, sponge, or brush, and there is a considerable skill involved in obtaining these types of finished surface.

The main components of render are cement, sand, and water, but there are many different mixes that have additives included for various purposes. Any general-purpose cement can be used, but the sand should be free of impurities. A coarser sand is used for the base layer, and a finer one for the finishing coat.

On older buildings, a lime mortar may be used, especially if lime was used in the original building. The lime is used instead of the cement and a lime mortar allows the wall to breathe which lets any moisture escape from the wall, but lime mortar takes longer to dry than sand and cement. Lime mortar is also more flexible than sand and cement and is less likely to suffer from cracking.

Render is often mixed using a cement mixer, but there are different types of render which are supplied ready-mixed in tubs, some of which have had pigments added for colouring purposes. This type of render has the distinct advantage that there will never be any need to repaint the render, as the colour will last as long as the render does. Indeed, some renders can have a lifespan of up to 50 years.

Render is often applied using a trowel, but it can also be sprayed on which produces a finished render in far less time, so saves on labour costs.

Another type of render is an acrylic render. This is any type of render that has had acrylic resin added to it. Acrylic resin is a type of plastic and it gives the render some elasticity which helps to prevent the render from cracking. It also helps to make it water and stain resistant. In many cases only one layer of acrylic render is needed to make a wall look great for up to 20 years. However, acrylic render does have one drawback and that is that it is not permeable so it cannot allow the wall to breathe. So, quite simply, it cannot be used on older walls which are of solid brick and do need to be able to breathe and let any moisture out.

Another form of render is flexible synthetic silicone which, as the name suggests, contains silicone. As it is flexible, it is similar to acrylic render in the sense that it is resistant to cracking. It can be applied at varying thicknesses starting from as thin as 1mm which means that you don’t need as much material as you do with other renders. One layer that thin can last for up to 50 years. Flexible synthetic silicone render is also extremely weather resistant and is a good choice for exposed areas and coastal areas which can suffer from salt and spray.

Another very big advantage of a silicone render is that, unlike acrylic, it is semi-permeable so it can be used on walls which need to be able to breathe.