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Using EWI Pro renders on Render Carrier Board

Render carrier boards provide a solid base on which our render systems can be installed. There are lots of different types of render board available here in the UK, and the good news is that our EWI Pro renders and adhesives can be used on pretty much all of them! Render carrier boards are often used when constructing timber frame or steel frame buildings. Our renders are suitable for use on boards including Bluclad, Renderflex and Rendaboard, but for a list of approved boards, see our ultimate guide to render carrier boards.

Why use render carrier board?

The render carrier board provides a stable base on which the new render top coat can be applied. The carrier boards are characterised by high tensile strength which resists bending to prevent cracking and deformity, but they also tend to be breathable, moisture resistant and non-combustible. In many cases too, the render boards can take a considerable amount of impact force before cracking ensuring that your home will stand up to the elements!

Render carrier boards often are manufactured in two thicknesses 9mm and 12mm; however we recommend using 12mm render boards where available (Blueclad, for example, only do a 10mm board). The extra thickness of the carrier board just gives it that bit more strength – so it’s always worth using if you get the option.

Joining neighbouring render carrier boards

The render carrier boards tend to be attached to either wooden battens or a steel frame and are staggered. It is good practice that the carrier boards should also have a 3 – 5mm gap between them and their neighbouring board. We suggest using a 5mm window packer as a gauge to get it looking neat and tidy!

Once the boards are attached to the timber/steel battens, it is time to mesh the joints. The easiest way to do this is to cut 200mm strips of our EWI-66640 Fibreglass Mesh and use an approved fibreglass mesh tape to hold these in place. After this, it is then time to apply the basecoat to the render carrier boards.

EWI-225 Premium Adhesive is perfect for render carrier boards!

Our EWI-225 Premium Adhesive is the preferred product for basecoating the render carrier boards. The reason for using the EWI-225 is that the carrier boards don’t require priming before applying it. The EWI-225 is incredibly strong and has unsurpassed adhesion to the carrier boards, so once you put it on the boards you can be sure it won’t go anywhere. If you are one of our approved installers, we will provide 10 year warranties on our EWI-225 Render-only system – a nice selling point for customers.

Apply the EWI-225 to the render carrier boards using a notched trowel. This is the easiest way to ensure you apply the same thickness of adhesive across the boards. A 10mm notched trowel held at 45 degrees to the render carrier board will give you the required 6mm depth of adhesive.

Embedding the Fibreglass Mesh in render carrier board systems

Once the adhesive has been applied, it is time to sink the EWI-66640 Fibreglass mesh into it. The mesh is embedded in the adhesive from top to bottom rather than horizontally from side to side. You will notice on the rolls of EWI-66640 Fibreglass Mesh there are markers at each end – these signify the 100mm overlap required when embedding the layers of mesh. They should always overlap the previous piece of mesh embedded by 100mm.

To embed the mesh, turn the notched trowel over so you have the straight edge of the trowel and draw it up from the bottom of the mesh you are looking to embed. By drawing the trowel up and pressing down on the mesh, adhesive will be pulled through the mesh and it should disappear. Once completed, there should be no visible signs of the fibreglass mesh anywhere – it needs to be completely embedded before applying the top coat primer.

Once the EWI-225 Adhesive has gone off, it is time to prime the wall, prior to applying the final top coat of render. The product that is used to prime the wall is our EWI-333 Silicone Primer which can be painted on or applied using a roller. If you are using a very vibrant colour, then we suggest tinting the primer too – otherwise the white primer may show through the final top coat render (hopefully it won’t, but the top coat is very thin so there is a small risk this can happen).

Applying render to render carrier boards

So, having left the primer to go off, you are now ready to apply the topcoat render. This is the decorative layer that ensures the render system is weatherproof. Our silicone renders (EWI-075 Silicone Render or EWI-040 Silicone Silicate Render) are through-colour renders, meaning they are coloured straight out the bucket (you don’t need to paint them after). The silicone renders are also breathable and hydrophobic, so they self-clean. Once the render has been applied to the wall surface, you then need to rub the render using a plastic render float to give the required texture to the render. The result is a maintenance-free, aesthetically pleasing finish!

It is also worth mentioning that we do all our colour tinting here in the UK, meaning we can get you coloured render the very next day!

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