thin coat render

As we are well into the 2020s, the demand for insulation, external decorative products and coloured render is rising. The 2020s has seen another generational shift, as renderers are moving away ever more away from traditional cement and choosing various coloured render or insulated render products.

In this industry, the terms ‘coloured render’ and ‘insulated render’ are talked about a lot. The terms are often used interchangeably, however subtle differences do exist and in this blog we are going to take a look at these in a bit more detail, so that the appropriate solutions can be used on your next and upcoming project.

What is coloured render?

Coloured render refers to render that is coloured right through it’s final decorative coat in one uniform appearance. Sand and cement render is not coloured render. When we refer to coloured render we usually refer to the EWI-010 Acrylic Render and the EWI-075 Silicone Render (also known as thin-coat renders), which form the final finish as part of a multi-layer build-up; or we refer to EWI-090 Monocouche Scratch Render, which is also coloured through and can be applied either on its own or on top of a basecoat preparation layer. Our coloured renders can now be matched to NCS colours as part of our colour matching service!

Acrylic Render, Silicone Silicate Render, Silicone Render, Premium Bio Render and Nano Drex Render are all examples of coloured renders. Coloured renders are also referred to as thin-coat renders. 

The next section talks about the nuances in the family of coloured renders. 

What are the differences in the coloured render types?

The acrylic or silicone renders usually come in wet bucket form and are manufactured in a standard white colour. To produce the coloured render, the acrylic or silicone renders go through a tinting machine, which consists of a pigment dispenser and a shaker. The coloured pigment is dispensed into a bucket in a controlled environment and this bucket is shaken-up by the shaker to produce one uniform colour throughout.

Monocouche scratch renders, come in a dry format, usually in 25kg bags – these are pre-mixed in different colours, and need to be mixed with clean potable water to make it ready for application.

Since monocouche render is pre-mixed with different colours, you will probably not be surprised to learn that the numbers of colours available with this type of render is limited. In fact, when going with a monocouche coloured render, you can pick from about a dozen or so different colours, but if you opt for the thin coat coloured renders you can literally pick from thousands of colours.

Achieving different types of finishes

Another difference between monocouche and thin coat renders is the type of finish that is achieved. While the thin coat renders, usually leave a textured, slightly grained type finish, the monocouche scratch renders achieve a pitted effect, by effectively leaving little scratches on the surface (hence often referred to as scratch coloured render). Both finishes look great, so choosing which coloured render to go for normally comes down to which look the end-user prefers.

However what we have found that since the turn of the 2020’s more and more customers are turning towards the thin coat coloured renders due to their additional hydrophobic and flexible qualities.

Difference in application procedure

The other differences between the two different coloured renders is how they are applied to the wall. The scratch render is in applied at a thickness of 18mm and scratched back using a scratch render scraper to give a final thickness of 16mm. Conversely the thin coat renders are applied at a thickness of 1-3mm onto a flexible basecoat layer (basecoat + embedded mesh). This means that a bucket of thin coat render will go far further in terms of coverage than a bag of monocouche scratch coloured render when applied to the wall.

Our dash receiver is also bagged like the monocouche scratch render and comes in different colours, but the decorative pebbles that stick on the outer surface form the main part of the decorative feature so the amount of actual dash receiver you can see is limited.

The “dash look” is rather dated and was quite popular in the 1970s and 1980s. However we do still have requests occasionally is parts of Wales or Scotland. 

The second part of the blog now explores what insulated render is.

What is insulated render?

Very often when we refer to insulated render, we refer to a coloured through render backed on an external wall insulation material. This external wall insulation material can either be lightweight EPS, stone wool (mineral wool), K5 phenolic or wood fibre insulation board. The insulated render part is the final decorative layer that sits on top of the reinforcement layer, which in turn sits on top of the insulating material.  The whole system in therefore an example of an insulated render system or a external wall insulation system (EWI).

Insulated renders as parts of external wall insulation systems first introduced the “coloured render” component to the UK as part of the overall concept in the early 1990s. 

What are the differences in the insulated render types?

There are differences in insulated render types, which are characterised by the differences in the build-up – starting from the insulation material, to the reinforcement layer and then a variation in the decorative look.

For example, insulated renders can use one of the following insulating materials: EPS, Mineral Wool, K5 phenolic and Wood fibre insulation. Phenolic insulated has the best thermal insulating value followed by the EPS, Mineral Wool and then the Woodfibre. On timber backed systems you would want to go for something like the woodfibre, whereas if you are insulating traditional brick, then you have a choice of all four depending on the individual choices and preferences.

Basecoats and reinforcement mesh may vary to achieve a different preparatory coat ready to receive the final coat. Basecoats can either be in the grey or white adhesive types. Also, the system build-up may contain a slight variation in the weight of the fibreglass mesh, with one coat mesh or two coat mesh being used for different impact resistance requirements.

Achieving a nice and level basecoat is absolutely crucial in getting the best type of aesthetic finish on the final silicone or other thin coat texture. In addition depending on the use of the wall being reinforced, 2 layers or fibreglass mesh can be installed or a panzer mesh instead of one regular level of mesh to give the overall wall additional structural strength. 

Coloured renders like the thin coat silicone or acrylic can sit on top of an insulated render system and work very well. Monocouche scratch render can also sit on top of the reinforcement layer, but it is not commonly specified due to the weight/ load of this final coat of the coloured through render. Some manufacturers do specify monocouche or scratch render on top of insulation, but we are a bit sceptical on its long term performance due to the load and flexibility issues.

Can the render itself be ‘insulating’?

In certain and rare circumstances, the coloured render itself can contain special insulating properties, which when used as part of the render build-up can be considered an insulating render. These coloured renders don’t necessarily have an insulating material behind it. An example of a coloured render that is also an insulated render, is using a basecoat that contains a certain amount of the following ingredients (not limited to this list): perlite, EPS, cork or aerogel, and the product itself has a declared lambda value (ƛ) on the product packaging.

Remember the lower the lambda the better the insulating property of the material. For example the K5 Phenolic board has a declared lambda of 0.018-0.020 whereas the Mineral Wool is 0.036. Therefore we can conclude that the K5 phenolic board is a better insulator than the Mineral Wool for a given level of thickness.

An example build-up of coloured render with insulating properties: the EWI-520 Insulating Basecoat (limited availability and special orders only) with a layer of fibreglass mesh to give the layer flexibility; finished off with 1.5mm of the EWI-075 Silicone Render.

Limitations of insulated render materials

Although the insulated coloured render in this example has insulation properties, it would not replace the degree of insulation associated by installing a full external wall insulation system. You could install this type of system in areas of difficult access or where it would be tricky to thicken the walls by a certain degree due to width (boundary) restrictions around the property.

Additionally you may want to use the insulated render on the window reveals, where applying a 20mm insulation board is not a practical situation. You can also have these details between openings and facias & gutters. 

Coloured renders and insulated renders in summary

As discussed above coloured renders and insulated renders are used interchangeably in the industry but you do have subtle differences. Coloured render refers to the cement-based plaster applied either as a basecoat and a thin-coat decorative finish; or to a one-coat Monocouche Scratch Render applied in one pass onto the substrate. Therefore there would be additional external insulating boards stuck on the substrate waiting to receive the coloured render itself.

Insulated Render usually refers to an external wall insulation system that not only contains a coloured render, but an insulation material that is adhered to the substrate. This insulation material can EPS, Mineral Wool, K5 Phenolic or Wood fibre insulation.

Coloured render can also have insulating properties, but it must be declared on the packaging. However this can be used to take the edge of a substrate rather than as a prime insulating material for the purposes of thermal insulation. I.e. applying 100mm of insulating cement based plaster is just practical. 

2020’s outlook for coloured render

We are finding that the 2020’s have brought about a significant increase in demand for coloured render finishes either as a render itself or with an insulating board applied. Sand & cement while still widely used is slowly being phased out due to the fact that once applied does not have the benefits offered by coloured and insulated renders.

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