There are several reasons:
1) Immediate protection from the elements. Raw polystyrene, if left un-coated will surface degrade and reduce adhesion of base coat renders, causing possible delamination of renders.
2) The first coat of render applied to polystyrene panels is crucial. This render must have superior adhesion and flexibility than standard renders for brickwork for instance. In the Unitex factory, EPS sheets are transformed into Unitex Base Board sheets by applying alkali resistant fibreglass mesh and a strongly adhering and flexible polymer modified cement coating with a consistent film build with a toothed profile. The special toothed profile makes it easy for the applicator to trowel on the base coat levelling render, (Uni-Dry Cote BBR 8.5 kg), at the recommended film build once the Unitex Base Board sheets have been fixed to the frame, ensuring that only the most flexible render on the market with the greatest adhesion has been applied on your project.
3) Raw polystyrene sheets should not be coated whilst wet as this prevents renders from adhering to the surface. This can cause major delays during winter months. Unitex Baseboard is manufactured inside under controlled conditions.
4) System warranty’s for your peace of mind, Unitex Baseboard is a risk free proven surface.
5) Speed. Unitex Baseboard saves time as the first coat of render is already completed.