Our EWI Pro external wall insulation system is made up of a combination of adhesives, insulation materials, coloured renders and paints, but for many people they just want to give their home a facelift rather than go the full hog and insulate the house at the same time. The good news is that when rendering your home, very few products are needed and also the process itself is very simple!
What materials are needed when rendering your home?
There are 6 basic products that you need to render your home (although you may not need the levelling mortar depending on the state of the wall):
1. Levelling Mortar (EWI-260)
2. Substrate Primer (EWI-310)
3. Basecoat Adhesive (EWI-220)
4. Fibreglass Mesh (EWI-66640)
5. Render Primer (EWI-333)
6. Render Topcoat (EWI-040)
Preparing the wall prior to installing render
There are two ways in which you can prepare the wall – we would always recommend using primer, which we will cover in a moment, but you can also use levelling mortar if necessary.
Levelling Mortar (Optional)
The purpose of the levelling mortar is pretty much what it says on the tin – it is used to level out the wall before applying the basecoat and render layers to the system.
Our levelling mortar can be used on cracks up to 50mm. It comes in a 25kg bag and is a dry mix. Each 25kg bag of levelling mortar needs to be mixed with 6 litres of water prior to using it. It can be applied with standard trowel, and the great thing about it is that even when it dries, shrinking is only minimal so it keeps it shape in the filled cracks. We recommend using the levelling mortar over the whole surface when using our render systems over pebble dash.
Normal coverage is approximately 4m2 per bag when it is applied to a depth of 6mm, but obviously, coverage will vary dramatically from job to job.
Applying substrate primer before rendering your home
The substrate primer is used first to fulfil 3 roles:
1. Stabilise the substrate
2. Reduce the rate of absorption of the substrate
3. Allow the basecoat to key into it
Our substrate primer is known as Universal Primer (EWI-310) and comes in 20kg buckets. It is applied to the wall surface using either a brush or a roller and helps stabilise the substrate. We would always recommend using a wire brush to help remove any organic or loose debris before applying the primer, but even if this step is ignored, the primer will help solidify any loose debris left on the wall.
When the basecoat adhesive is applied to the wall, it goes on as a wet mortar. Another purpose of the primer is to stop all the moisture from the adhesive being drawn into the wall. The issue is that the adhesive will go off to quickly if the primer is not used, which is okay if you work quickly, but we know that most renders want a bit of time to get the basecoat layer nice and flat.
The final purpose of our universal primer is to allow the basecoat to key into the wall. The primer has silicate (essentially sand) particles which give the surface of the primer a bit of texture when it dries. This allows the basecoat adhesive to key into the primer and form a stronger bond with the wall. This is particularly important if the primer is being applied to a very smooth wall.
Once the wall has been primed (and is hopefully now level if the levelling mortar was required) it is time to add the basecoat layer.
Adding a basecoat layer
The basecoat layer is the most important layer when you are rendering your home. This consists of a 6mm layer of basecoat adhesive with an embedded fibreglass mesh. The EWI-220 Basecoat Adhesive is applied to the wall using a notched trowel and then strips of fibreglass mesh are embedded into it.
The basecoat adhesive comes as a dry mix in 25kg bags. 6 litres of cold water needs to be added to this before it can be applied to the wall. It needs to be mixed with a paddle mix until a smooth paste forms and this needs to be left for 10 minutes before another quick mix is done prior to applying it to the wall.
The fibreglass mesh comes in 50m rolls and is 1m wide. Each strip needs to overlap the previous strip by 100mm and we recommend installing the strips vertically down the wall. While the adhesive is still wet, gently press each strip into the adhesive, and then turning the notched trowel over draw the flat edge up over mesh – this will embed the mesh into the adhesive by drawing adhesive through gaps in the mesh.
This layer needs to be completely flat before applying the top coat render as the render layer will only be 1.5mm thick; therefore any bumps and lumps in the basecoat layer will be visible within the render if they are not taken out!
We mentioned previously that the basecoat layer is just about the most important part of our render only system – and the reason for this is all due to flexibility. Our render systems don’t crack – this basecoat layer moves with the building and together with the flexible top coat it offers an incredibly durable system once installed on your home.
Priming the basecoat
Before rendering, the basecoat needs to be primed. The type of primer should match the render you will be using. The primer is applied with a brush or roller once the basecoat has dried completely.
The final stage! Your chosen type and colour of render is applied to the wall with a trowel and then textured using a plastic float. The result is a fresh new look for your property, and a protective coat against weather damage.