The EWI Pro EPS external wall insulation system is made up of several components – including everything from the preparation materials, the insulation (itself), the basecoats and top coats. It is absolutely paramount to use the right components in the installation process to ensure the integrity of the system and to uphold all the necessary system designer product warranties.
Using the wrong EWI Pro components may not appear to be a problem initially, but can lead to problems further down the line. We recommend you follow the step-by-step installation guides to achieve the optimal end solution.
The EWI Pro EPS external wall insulation system is a BBA approved system and specifies the name and number of each component to use. The BBA document goes into quite a lot of detail, including how to apply the adhesive to the insulation, setting out the number of fixings per EPS board and how much basecoat to add before the mesh is sunk.
The following section introduces each component of the system and goes into a bit more detail on how it is applied in the live job.
Priming the walls with EWI Pro Primers
If you are going for a silicone based render finish, then we recommend using the EWI-333 SISI Silicone Silicate primer. For mineral and acrylic renders, you should use EWI-330 Mineral & Acrylic Primer.
Although the priming of the walls is outside the scope of the BBA, it is highly recommended to undertake before any insulation is actually applied. Priming the walls ensures that the walls are prepared for the insulation as the product contains quartz crystals, which serve to provide a nice abrasive surface for the insulation to stick to.
Biocide products can be added to the primer in the application stage – this serves to remove any biological growth on the walls and prevents their build up. This is great to do if your walls have had previous attacks from biological agents.
Priming is also good to do to cover over any hairline cracks and bind any loose surface debris to the substrate. A nice and firm surface is a fantastic starting point for the insulation, which will make the adhesion stage a ‘walk in the park’.
Sticking the EPS using the EWI Pro adhesive
When applying the EPS boards to the wall you can use the EWI-210 EPS Adhesive or the EWI-220 Basecoat. You will need to follow the EWI Pro installation standard when dabbing the adhesive on the back of the board. The adhesive needs to go all round the perimeter of the board and have at least 2 or 3 dots dabbed in the middle of the board.
Both the EWI-210 and EWI-220 need to be mixed with water and prepared before the works start. The packs of adhesive and basecoat come in 25kg bags and each one will cover about 3m2. When mixing the adhesive make sure you use a low speed mixer to start off the process. Once mixed set it aside for at least 10mins to allow the fibres in the material to bond – then you should be ready for the installation process.
Installing the mechanical fixings
The mechanical fixings or anchors are produced by specialist companies for the use in external wall insulation system design. Traditionally plastic fixings were quite popular as anchors but over time ones with metal rods have also been used. The metal and plastic fixings require quite a bit of preparation works and can add quite a bit to the installation time. For example, to avoid the cold bridging each of the ends of the plastic head should be capped off with a rounded piece of EPS plug – stuck together with foam adhesive.
Due to this extra work with the traditional fixings, this is the reason that we fully endorse the EcoDrive (self-drive) fixings. With the EcoDrive fixings you still have to prepare the holes in the walls for the wall plugs, but you can then use a mechanical screw-drill to self-drive the fixings into the insulation and the walls.
According to EWI Pro you should use 5.5 fixings per m2 of EPS board. This together with the adhesion stage in the previous process will provide a nice and robust insulation layer.
Sinking the fibre glass mesh into the basecoat
Installing the fibre glass mesh into a layer of basecoat binds the insulation layer together and prepares a nice substrate ready for the top coat.
With the EWI Pro system we recommend using the EWI-220 EPS Basecoat. Please do not use the EWI-210 Adhesive as this will not work optimally and will void you the manufacturer’s warranty. Just like the adhesion layer the basecoat is prepared the same way – adding the bag of powder to the set amount of water.
For this stage, using a notched trowel, the fibre glass mesh is sunk into the layer of basecoat. For more details, please refer to the EWI Pro Installation Manual for EPS.
The EWI-220 EPS Basecoat is designed to dry quickly but you should leave this coat to set for at least 48-72hrs. If you have been using the EWI Pro products for a while, then use your best judgement. Sometimes you need to make a call based on the atmospheric and site conditions and add more/less time to this process.
Prime using the SISI or the Mineral / Acrylic primers
As mentioned in the previous section the type of primer you use is determined by the top coat. For example, for silicone silicate render we recommend using the EWI-333 SISI Silicone Silicate Primer; for mineral render we recommend using the EWI-330 Mineral & Acrylic Primer.
The primer can be applied mechanically with a roller or a brush. If you use a spraying machine, then you can use this too.
Leave the primer layer to dry for at least 24hrs before applying the top coat.
Applying the top coat render
You can apply different types of finishes – such as render, scratched render, dash or brick slips. But to keep things nice and simple we recommend the grained render every time.
The EWI Pro render comes in different grain sizes – available in 0.5mm, 1.0mm, 1.5mm, 2.0mm and 3.0mm. The 0.5mm render is virtually smooth with the 3.0mm render being quite rough. Bigger grained renders are actually applied with a thicker coat – the thickness of the coat render should be synonymous with the grain size. So when applying 2.0mm render the thickness of the coat should be no more than 2.0mm thick.
Most installers quite like installing the 1.5mm grained render as it is sits nicely in the middle of the other grain thicknesses and aesthetically it looks pretty good as well.
Different types of EWI Pro renders available:
- EWI-040 Silicone Silicate Render
- EWI-075 Silicone Render
- EWI-010 Acrylic Render
- EWI-060 Mineral Render
The renders are sold in liquid form and come in 25kg buckets, apart from the mineral render, which is cement based and requires another layer of silicone paint to complete the installation. The liquid based renders can be applied straight onto the walls and can be coloured with different pigments – so you can achieve any colour of wall that you like.
Mineral render requires painting!
When you have applied the EWI-060 Mineral Render on the wall, you will need to wait for it to set before painting it. The render is mixed a bit like the adhesive and the basecoat – using a low speed mixer, adding the powder to a bucket of water.
When the render is dried, we recommend using the EWI-004 Silicone Paint, which in fact can be coloured to achieve any coloured finish the customer wants.