How can I tell when plaster is dry?

Wet plaster appears dark. As it dries, it turns progressively lighter — from dark brown/pink to pale pink to white. The plaster is fully dry when the entire surface is a uniform light colour with no dark patches. Touch the surface — it should feel dry and not cold. Use a moisture meter for certainty: it should read below 1% before painting.

Can I speed up plaster drying?

Yes, but carefully. Open windows for cross-ventilation, use a dehumidifier (the most effective method), and maintain a room temperature of 18-22°C. Do NOT use direct heat sources like fan heaters or blow-torches — rapid drying causes cracking. A dehumidifier is the safest way to speed up drying by 30-50%.

What happens if I paint over wet plaster?

Painting over damp plaster traps moisture behind the paint film. This leads to peeling, bubbling, staining, and potential mould growth. The paint will not adhere properly and will need to be stripped and re-done. Always wait until plaster is fully dry and apply a mist coat (diluted emulsion, 70:30 paint to water) before the full coat.

What temperature should a room be for plastering?

The ideal temperature for plastering and drying is 15-25°C. Below 5°C, plaster can freeze before it sets, causing it to fail. Above 30°C, it may dry too quickly and crack. In winter, gently heat the room before and during plastering. Avoid draughts during application but open windows for drying after the plaster has set.

Plaster Drying Time Estimator — How Long Does Plaster Take to Dry?

How We Calculate This

Our plaster drying time estimator uses the general rule that gypsum plasters take approximately 1 day per 1mm of thickness to fully dry under moderate conditions. We then adjust this based on room temperature, ventilation, and plaster type.

The formula

Drying time (days) = Thickness (mm) × Plaster factor × Temperature factor × Ventilation factor

Key factors

Thickness: The primary factor — thicker plaster takes proportionally longer to dry
Temperature: Optimal range is 18-25°C. Below 10°C drying slows significantly; below 5°C there is risk of frost damage
Ventilation: Good airflow (or a dehumidifier) can speed drying by 25-50%. Poor ventilation significantly slows drying
Plaster type: Multi-finish (skim) dries fastest; bonding coat is thicker and slower

Typical drying times

2mm skim coat: 2-3 days
8mm bonding coat: 8-12 days
13mm one-coat plaster: 13-18 days

Tips for faster drying

Use a dehumidifier — the most effective and safest method
Open windows on opposite sides for cross-ventilation
Maintain room temperature at 18-22°C with gentle background heating
Do NOT use fan heaters, blow-torches, or other direct heat sources
Do NOT plaster in freezing conditions

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Verify with your supplier.

Plaster Drying Time Estimator — How Long to Dry?