PAINTING PLASTER HOMES
Allied Exteriors specialises in painting plaster homes and maintaining exterior plaster cladding systems (often called monolithic cladding). The paint coating system is an integral part of an exterior plaster cladding system and is critical to the weathertightness of your home.
We maintain and paint around 200 plaster homes annually and have painted over 4300 buildings since we started our business in 2006.
Plaster Substrate Preparation
Substrate preparation is always the key to ensuring the long-term performance of a paint coating. Defects within the exterior plaster system such as fracturing, poor detailing, lack of control joints, missing flashings and poor terminations must be rectified to ensure a sound substrate for the paint system.
With a specialist plaster repair division, we have the experience and expertise to recognise such issues and ensure appropriate plaster repair solutions are completed prior to painting your plaster home.
What Paints Do We Use
Typically, we use Resene X200, Dulux 201 Elastomeric or Wattyl Grano Impact for painting plaster homes. These paints are all specifically designed for plaster cladding systems. The Resene X200 paint is fibre reinforced to mitigate the paint membrane from tearing should minor hairline fracturing of the plaster substrate occur. Similarly, the Dulux 201 and the Wattyl Grano Impact have elastomeric qualities which allow them to bridge minor hairline fractures in the plaster system. We use StoLastic, Resene X400, Wattyl Granoskin and a variety of other elastomeric paint systems for higher risk areas and projects where a higher degree of elasticity are required (i.e. these paints are thicker and can bridge larger fractures before breaching).
Elastomeric paints tend to have slightly less adhesion to the underlying substrate (than standard acrylic paints) and rely upon a thicker film build to perform the elastomeric function (stretching over minor fractures). Applying an elastomeric paint too thin will prevent the coating from performing as designed. The thicker film build required for elastomeric paint systems makes them less permeable and more prone to bubbling should moisture be present in the substrate. When the sun hits the wall, the moisture turns to gaseous vapour and expands in volume. If that vapour cannot permeate through the paint membrane quick enough – bubbling occurs. Hence, it is critical plaster substrates be properly prepared prior to repainting.
Where we perceive there to be a higher risk of moisture in the substrate or where we have concerns about the existing paint coatings (i.e. excessive film build or deterioration of the coatings), we would recommend using a more permeable acrylic paint coating to reduce the risk of the paint bubbling.
Paint Colour Selection
Paint colour selection is important as each plaster system substrate (such as masonry, fibre cement sheet, polystyrene & AAC) has a different ability to disperse heat from the sun away from the plaster system. Excessive heat generation in a plaster system leads to thermal fracturing and will compromise the long-term performance of the both the plaster and paint coating system.
Each paint colour has a Light Reflective Value (LRV). Lighter colours have higher LRV ratings, reflect more sunlight and absorb less heat. Darker coloured paints have lower LRV ratings and generate more heat in the plaster system. For plaster systems installed over a fibre cement sheet substrate, the building code requires paint colours to have an LRV of 40% or greater. There is no such requirement for solid masonry substrates. However, industry experience has shown us that painting plaster systems in very dark colours will create problems.
Where clients wish to use darker colours, there are various ways to mitigate the risk of thermal fracture by using acrylic plasters, heat reflective substrates and heat reflective coatings such as Sto X-Black and Resene Cool Colours. However, these products only mitigate the risk - they do not eliminate it. Should you be considering using a dark colour paint, please contact us to get accurate project-specific advice.
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