Render Carrier Board with Topcoat Finish

Carrier board systems create airflow between substrates and are installed on timber-framed buildings or those with damp. Fassa Render carrier-board system products used are easy and great to work with, especially our carrier board, due to its lightness.

Below we have created a step-by-step guide, to provide you with the information needed in completing carrier board with topcoat finish system.


Our Gypsotech®Externa Board is a lightweight render board that due, to its dimensions, can be handled by one person alone. The boards must be placed horizontally and perpendicularly onto your battens leaving a 1-2mm gap and fixed with board screws onto the battens.


After leaving a 1-2mm space in-between your boards, you will need to reinforce the joints with an A96. Once done, you will need to apply 15cm wide strips of Fassanet 160 alkali-resistant reinforcing mesh. A 20cm wide slurry coat should be applied over the top of the joints.


Once steps 1 & 2 are complete and the materials have cured, a basecoat of A96 can be applied. Used to go onto render boards because of its high polymer content, improved adhesion and workability, A96 is the perfect product to bond and skim-coat onto render board system. We advise applying A96 onto the board using an 8mm notched trowel, covering the Gypsotech®Externa Board completely.


While the 1st Basecoat layer is wet, embed Fassanet160 mesh following a top-down approach. Meshing at this stage prevents hairline cracks in the render, gives higher impact resistance and decreases the chances of delamination.


A96 is then thinly applied over everything to level out and smooth the surface again before moving onto the final stages.

Step 6: PRIMER.

FX526 is a pigmented primer undercoat that can be used on cement-based plasters and renders. FX526 can be mixed up to 365-colours, creating a uniformly coloured surface before topcoat is applied. Dilute with a minimum of 5% water before rolling it onto the surface.

Step 7: TOPCOAT.

RX561 is a silicone topcoat that gives the perfect finish on Gypsotech®Externa Board. RX561 delivers a long-lasting finish thanks to its flexible and hydrophobic properties, increasing the time needed between maintenance cycles. RX561 comes in 1.5mm grain and can be mixed in 365-colours. You can apply our topcoat either by hand using a trowel or spray gun.

Before using any Fassa Bortolo products or systems, we always advise checking the data sheets available on our website.

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