Specification guidance
Polished Plaster As A Specification Category
Polished plaster is a description of a result rather than a recipe. Because nothing in the term fixes the material, the layer count or the sheen, the whole risk in specifying it sits in how precisely it was written down.
What the term does and does not tell you
Polished plaster covers lime-based Venetian finishes, gypsum-based decorative plasters and modern acrylic-modified products, all of which can be burnished to a sheen. They differ in breathability, durability, repairability and cost, and a specification that says only polished plaster has selected none of those.
For a developer or a designer this matters commercially. Two contractors can both meet a specification that says polished plaster and deliver walls that look and cost nothing like each other. Naming the material family removes that ambiguity in one line.
- ✓Name the material family: lime, gypsum-based or acrylic-modified
- ✓State the sheen level against a signed-off sample
- ✓State the layer count expected
- ✓State the protective treatment: wax, sealer or none
- ✓State the substrate preparation standard required
Controlling sheen properly
Sheen is the variable clients feel most strongly about and the one most loosely described. Matt, satin, semi-polished and high polish mean different things to different applicators, and the words alone will not protect you.
The workable method is a physical control sample, produced by the applicator who will do the work, signed by the client and kept on site for the duration. Everything is then compared to that panel rather than to a recollection of a conversation. On any project of scale this is the single most valuable half hour spent.
Keep the signed control sample on site until practical completion. It is the only objective reference anybody has.
Where each material family fits
None of these is universally better. A listed interior with solid walls calls for a lime finish. A commercial corridor that needs to survive contact points towards a modified system. A dry feature wall on a tight budget may be perfectly served by a gypsum-based finish.
- Lime-based
- Breathable, traditional, best depth, suits period and high-end work
- Gypsum-based
- Interior dry areas only, smooth and economical, not for wet zones
- Acrylic-modified
- More robust and water-tolerant, less translucent depth
Practical checks before work starts
The lighting point is regularly overlooked. A wall washer placed close to a polished surface will show every trowel pass, which may be exactly the drama you want or may be an unpleasant surprise at handover. Decide deliberately, and if possible test the lighting against the control sample.
Protection through the remaining programme deserves the same attention. A finished wall standing for weeks while joiners, electricians and decorators work around it will collect damage unless someone owns the responsibility for covering it. Naming that party in the contract, rather than assuming it, avoids the familiar argument about who marked a surface that nobody saw happen.
- ✓Confirm the substrate is flat enough for the sheen level agreed
- ✓Confirm the room can be kept clean and dust free during application
- ✓Confirm lighting positions, since a polished wall reveals every fitting angle
- ✓Agree who protects the finish through the remaining trades
- ✓Agree the cleaning regime and hand it over in writing
Specification questions
Write the specification tightly
Material family, layer count, sheen against a signed sample, protective treatment and substrate standard. Five lines that make a polished plaster specification enforceable. We are happy to help you draft them for a project.