Polished Plastering Guide

For a UK homeowner, this is an investment in "architectural jewellery." It transforms flat walls into tactile features that mimic the look of natural stone or polished concrete, adding significant aesthetic value to modern and period properties alike.

What Does the Work Involve?

• Substrate Preparation: Ensuring the base wall is perfectly flat, stable, and free from moisture or movement.
• Priming: Applying a specialist quartz or grit primer to provide the necessary "key" for the plaster to bond.
• Base Coating: Applying the first one or two layers to build the foundation and level the surface.
• Finishing Layers: Applying incredibly thin coats (often 3-5 in total) using a specialist stainless steel trowel.
• Burnishing: Using the edge of the trowel to compress the plaster, which creates the characteristic shine and "movement" in the finish.
• Sealing: Applying a protective wax or breathable sealer to enhance the colour and provide water resistance.

Typical Costs

Polished plastering is priced significantly higher than standard skimming because it is a specialist artisan craft. Prices are typically quoted per square metre rather than by the day.

Factors affecting the price include the height of the walls (requiring scaffolding), the complexity of the finish, and the number of external corners which require meticulous hand-finishing. Expect to pay a premium in London and the South East due to higher labour overheads.

How Long Does It Take?

• Small Feature Wall (up to 10m²): 3 to 4 days. This allows for essential drying time between the multiple thin layers.
• Medium Room: 5 to 7 days. The process cannot be rushed, as each layer must "cure" slightly before the next is applied or burnished.
• Curing Time: While the surface is touch-dry within 24 hours, it takes 7 to 14 days to fully harden and carbonise.

DIY or Professional?

Professional highly recommended. Polished plastering is an art form that requires years of training and a specific "feel" for the material. A DIY attempt often results in a patchy, dull finish that is incredibly difficult and expensive to fix.

While there are no specific UK regulations like Gas Safe for plastering, the work should adhere to British Standards for internal plastering (BS EN 13914-2). A professional will also understand "suction control" on different wall types, preventing the plaster from cracking or peeling.

Choosing the Right Tradesperson

• Check Portfolios: Look for high-resolution photos of finished work, specifically close-ups of corners and light reflections.
• Samples: A reputable installer should provide a physical sample board (usually A3 or A4 size) of your chosen finish before starting.
• Training: Ask where they trained; many top UK installers attend specialist academies in Italy or the UK.
• Questions to ask:
  • "Is the plaster lime-based or synthetic?" (Lime is more traditional and breathable).
  • "How many layers will you be applying?"
  • "What wax or sealer do you recommend for this specific room?"
  • "Can I see a sample in different lighting conditions?"

UK Regulations

• BS EN 13914-2:2016: The British Standard for the design, preparation, and application of internal plastering.
• Building Regs Part L: Relevant if you are applying plaster to the inside of an external solid wall, as it may impact thermal performance.
• Health & Safety: Lime-based plasters are caustic; your tradesperson should use appropriate PPE and provide a COSHH data sheet if requested.

Pro Tip: Always ensure your walls are "substrate ready." Polished plaster is so thin that any movement in the underlying wall will cause visible cracks. Many installers insist on over-boarding with moisture-resistant plasterboard first.

Common Problems

• Delamination: The plaster peeling away due to poor priming or dampness in the substrate.
• Ghosting: Dark patches appearing where the plaster has absorbed moisture unevenly from the wall behind it.
• Cracking: Usually caused by structural movement or applying layers too thickly.
• Poor Burnishing: A dull or "muddy" finish caused by incorrect trowel pressure or timing.

Frequently Asked Questions

Is polished plaster waterproof for bathrooms?

Yes, if specified correctly. While not suitable for the inside of a shower cubicle (due to constant high-pressure water), it is excellent for bathroom walls when finished with a specialist waterproof wax or sealer.

Can you repair a scratch in polished plaster?

It is very difficult. Unlike standard paint, you cannot simply "patch" polished plaster without the repair being visible. Usually, the entire wall section from corner to corner must be re-applied to ensure a seamless finish.

Does it require a lot of maintenance?

No. Once cured and sealed, it is very low maintenance. It can be wiped down with a damp cloth and mild detergent. Every few years, a fresh coat of wax can be applied to maintain the shine.

What is the difference between Venetian and Polished plaster?

The terms are often used interchangeably. "Polished plaster" is the broad category, while "Venetian" typically refers to the traditional high-gloss finish made with lime and marble dust.

Can it be applied over existing painted walls?

Yes, provided the paint is well-bonded and not flaking. The surface must be sanded back and a specialist grit primer applied first to ensure the plaster sticks to the smooth paint.

Is it eco-friendly?

Traditional lime-based polished plasters are very eco-friendly. They are non-toxic, low-VOC, and naturally mould-resistant due to the high PH level of the lime.