Acrylic render

What is acrylic render?

Acrylic render is a factory-prepared facade coating based on acrylic latex polymers suspended in water, supplied ready-mixed in tubs or drums. Unlike mineral render, which is a dry powder mixed on site, acrylic contains pre-blended synthetic binders and pigments that provide colour from day one. It dries by water evaporation to form a tough, elastic plastic film that flexes with thermal movement and resists cracking. Acrylic is commonly used on ETICS systems based on expanded polystyrene (EPS) insulation and on painted masonry facades where colour saturation and ease of application matter more than vapour permeability.

How does acrylic render differ from mineral and silicate renders?

Mineral render is bound by Portland cement and lime, hardens through chemical hydration, and is entirely vapour-permeable. Silicate render is bound by potassium silicate (liquid glass) and also remains highly vapour-permeable. Acrylic render is bound by latex polymers, dries purely by evaporation, and has lower vapour permeability. This matters: acrylic is safe on EPS insulation and painted masonry, but cannot be used on mineral-wool or vapour-open systems. Acrylic is also softer than silicate and more prone to algae on north-facing facades unless biocides are added.

Why does elasticity matter in acrylic render?

Buildings move constantly from thermal cycling and substrate settlement. Mineral renders are rigid and crack under movement; acrylic render is elastic, stretching slightly with the substrate without cracking. This makes acrylic popular in continental climates with extreme temperature swings. However, elasticity alone does not prevent all cracking: poor application or substrate preparation will still fail. Acrylic remains slightly softer than mineral render, making it more susceptible to mechanical damage and algal colonisation.

What colour options are available with acrylic render?

Acrylic renders are supplied in hundreds of colours, from pale pastels to vivid saturated hues. Pigments locked into the latex matrix do not fade as quickly as paint applied to mineral render; rich colours remain bold after years of weathering. Colour throughout the coating means minor wear does not reveal a different shade beneath. This advantage over mineral render's grey-to-paint workflow is significant for designers wanting consistent colour control.

Why is acrylic unsuitable for mineral-wool and vapour-open walls?

Acrylic render has low vapour permeability (sd 1–3 m, compared to mineral render at sd 0.3–0.5 m). This is fine on sealed EPS insulation, but mineral-wool ETICS relies on every layer remaining vapour-open so trapped moisture can evaporate. If acrylic seals the outer surface, water that enters during construction or from rain accumulates inside the mineral-wool layer, rotting the wool and masonry behind it. Similarly, on historic stone or timber buildings, acrylic render traps moisture and causes damage. The mineral-wool system's approval requires a vapour-open (mineral, silicate or silicone) render; acrylic cannot substitute without risking failure.

What is the algae and soiling problem with acrylic render?

Acrylic render is softer and more porous than mineral or silicate renders, absorbing water readily and providing a favourable habitat for algae and mould. On south- and west-facing facades where sunlight is strong, algae growth is slow because UV inhibits it. On shaded north and east elevations, especially in damp climates, algae and dark mould can cover a facade within one to two years. The render also traps airborne dust and salt, accumulating grime that is difficult and expensive to clean. Unless the acrylic was manufactured with biocide additives, the problem worsens yearly and becomes one of the most common complaints about acrylic renders in Nordic and Central European renovation projects.

Is silicone render worth the upgrade?

Silicone render combines acrylic's colour range and elasticity with superior durability and cleanliness. Its cross-linked structure is harder, more water-repellent, and more resistant to algal colonisation. A silicone-coated facade stays cleaner and withstands damp winters better. Silicone renders cost more than acrylic and require skilled application; consult system manufacturers for pricing and performance benefits. For north-facing facades or persistently damp climates where low maintenance matters, the investment in silicone may be justified. For south-facing or protected slopes, acrylic with biocides remains adequate.

How do the main facade renders compare?

What are the advantages of acrylic render?

Acrylic is easy and fast to apply; plasterers familiar with paint can work with it after minimal training. Ready-mixed supply eliminates mixing errors. Application temperature range is wider than mineral render, allowing work across a broader seasonal window. Elasticity tolerates substrate movement better, valuable on timber framing or settling buildings. Colour palette is vast and consistent. For south- and west-facing elevations in dry climates, or painted masonry facades on sealed substrates, acrylic delivers good value.

What are the limitations?

Acrylic cannot be used on mineral-wool ETICS or historic renovation work. Its softness and porosity make it prone to algae and dirt accumulation on shaded, damp facades, a chronic problem in Central Europe unless biocides are formulated in. Durability depends on correct application and regular repainting intervals set by exposure conditions and maintenance. Acrylic remains water-permeable; if water breaches the coating it dries slowly, risking substrate rot. Most importantly, acrylic must never be applied over mineral-wool thermal insulation as hidden moisture accumulation risks structural failure.

What are the typical application properties?