What is decorative plaster?
Decorative plaster is the umbrella term for finishing plasters and renders that are not trowelled smooth but given a visible texture, grain or special appearance. It is used on external walls, often over insulation or old brickwork (where it is usually called textured render), and indoors on walls and ceilings. The texture comes from the aggregate in the mix and from the way it is applied and worked. The Dutch term is sierpleister.
Types
- Float-finished render: applied with a trowel and rubbed with a plastic float; the grain produces a calm, granular surface.
- Scraped render: applied thickly and scraped open once it has firmed up, exposing the aggregate.
- Sprayed plaster: applied by machine, from fine to coarse texture, common on ceilings.
- Granite render: render with natural stone aggregate intended to resemble granite.
- Rock-faced render: coarsely worked render imitating a rough rock surface.
- Interior decorative plasters: such as polished lime plasters like Venetian plaster (stucco veneziano) and tadelakt, with a smooth, glossy, clouded look.
Binder and grain
Broadly there are two families. Mineral plasters (lime, lime-cement) and silicate renders are vapour-permeable and suit old mineral backgrounds. Synthetic-resin renders (acrylic, silicone resin) are more flexible and come ready-mixed; silicone resin render is water-repellent yet fairly breathable. The grain size, usually given in millimetres, sets how coarse the texture is and the minimum coat thickness.
| Mineral plasters (lime, lime-cement) and silicate renders | Vapour-permeable; suit old mineral backgrounds |
|---|---|
| Synthetic-resin renders (acrylic, silicone resin) | More flexible and ready-mixed; silicone resin render is water-repellent yet fairly breathable |
Application: tips and common mistakes
- Prepare the background. It must be sound, clean, dry and flat enough. Use the primer that belongs to the system; it controls suction and is often tinted.
- Watch the weather. Do not apply in frost, full sun, strong wind or rain. The plaster dries too fast or unevenly, causing colour differences and cracks.
- Work wet on wet per area. Finish a wall area in one go up to a corner, bead or masking-tape line. A break in the middle of a surface will always show as a joint line.
- Have enough hands. On large areas one person applies while another works the texture.
- Stay breathable on old walls. On solid old masonry, a mineral or silicate render is usually the safer choice.
- Stick to one system. Combine primer, render and any paint from the same manufacturer.
Related terms
- Scraped render
- Granite plaster
- Baroque plaster
- Facade rendering
- Render texturing
- Lime mortar
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