Plaster Calculator UK
Calculate plaster coverage, materials & project costs instantly
Plaster Coverage Calculator
Professional estimation for UK plasterers and decorators
Board finish and Multi finish use the same coverage. Bonding coat uses around four times the quantity for the same area.
Measure floor to ceiling height
Subtract 20% for doors and windows
Spillage & breakage
📋 Professional Plaster Coverage
- • Standard coverage: 1 bag (25kg) covers 10m²
- • Bonding coverage: 1 bag (25kg) covers 2.5m² (4x quantity)
- • Drying times: 24 hours between coats, 14 days before painting
- • Waste factors: 5-20% depending on surface condition and complexity
- • Material cost: ~£8.50 per 25kg bag (Q4 2025 UK rates)
- • Labour cost: £25-35/m² standard, £35-50/m² skim coating, £50+/m² specialist
- • Plaster types: Bonding, Finishing, Thistle, Lime, Artex textured
- • Temperature: Don't plaster below 10°C or above 70% humidity
Understanding Plaster Coverage & Costs
Professional plaster coverage is standardised at 1 bag (25kg) per 10m² for standard finishes. Bonding coats require approximately 4 times the quantity. This calculator helps you estimate materials and costs accurately based on standard coverage rates. Understanding waste factors, drying times, and project costs is essential for accurate quoting.
Key principle: Standard coverage is 1 bag (25kg) per 10m². Add 10-15% waste to prevent job delays and callbacks. Professional plasterers always order extra material for touch-ups and repairs.
Plaster Types & Typical Applications (Q4 2025)
Different plaster types have different applications and coverage rates. Choose the correct type for your project:
| Plaster Type | Bag Size | Coverage | Application |
|---|---|---|---|
| Board finish | 25kg | 10m² | Top coat on plasterboard |
| Bonding coat | 25kg | 2.5m² | First coat on blocks/brick |
| Multi finish | 25kg | 10m² | Premium finish coat |
| Lime Plaster | 25kg | 10m² | Period properties, breathable |
| Artex Textured | 25kg | 10m² | Decorative textured finish |
Note: Coverage rates vary by plaster type. Board finish and Multi finish share standard 10m² coverage; Bonding coat uses 4x more material (2.5m² per 25kg bag). Check manufacturer specifications for exact values.
Drying Times & Environmental Factors
Drying Schedule
- • Between coats: 24 hours minimum
- • Full cure: 5-7 days
- • Before painting: 14 days minimum
- • Before wallpaper: 14 days
- • Optimal: 28-30 days
Environmental Conditions
- • Temperature: 10-25°C ideal
- • Avoid below: 10°C (fails to dry)
- • Humidity: Below 70% (above slows drying)
- • Ventilation: Critical for drying
- • Cold: Add 50% extra drying time
Waste Factors & Best Practice
When to Use Each Waste Factor
- • 5%: Simple, smooth applications
- • 10%: Standard typical work
- • 15%: Complex surfaces, first-time
- • 20%: Poor substrate, damaged walls
Professional Tips
- ✓ Prime plasterboard before plastering
- ✓ Mix to consistent smooth paste
- ✓ Apply 2-3mm maximum per coat
- ✓ Order 10-15% extra for safety
- ✓ Store plaster dry (use within 6 months)
Frequently Asked Questions
Q: How much plaster do I need?
Use this calculator to enter your wall/ceiling dimensions (length and width in meters), select the plaster type, and set your waste factor (10% typical). The calculator instantly shows bags and weight needed. Standard: 1 bag (25kg) covers 10m² for finish plasters; bonding uses 4x more material (1 bag per 2.5m²).
Q: What's the standard coverage rate?
Standard UK coverage is 1 bag (25kg) per 10m² for board finish and multi finish. Bonding coats use approximately 4 times the quantity (1 bag per 2.5m²). This is the industry baseline. Actual coverage may vary slightly based on substrate, technique, and conditions.
Q: Why shouldn't I plaster in cold weather?
Below 10°C, plaster won't cure properly - it dries too slowly or not at all. High humidity (above 70%) also dramatically slows drying. Maintain 10-25°C temperature and ventilate properly for optimal results and 24-hour drying between coats.
Q: How long before I can paint after plastering?
Wait minimum 14 days before painting. For new plasterboard with finish coats, allow 14-30 days optimal drying to prevent paint failure, peeling, or dampness issues. Proper curing ensures paint adhesion and professional finish.
Q: What waste percentage should I use for my job?
Use 10% as standard baseline. Use 5% for simple smooth work, 15% for complex surfaces or poor substrate, 20% for heavily damaged areas. Professional plasterers typically add 10-15% extra to prevent job delays and have materials for callbacks.
Q: How do I estimate project cost?
This calculator provides material cost estimates based on Q4 2025 UK pricing. Standard 25kg bags of plaster cost approximately £8.50 retail (£7-9 range depending on supplier and brand). Professional labour rates average £25-35/m² for standard plastering, £35-50/m² for skim coat finishing, and £50+/m² for specialist work. Always obtain detailed quotes from local plasterers for accurate regional pricing.
Q: Should I subtract openings like doors and windows?
Yes, always subtract approximately 20% from total wall area for doors and windows. For detailed calculations, subtract: standard door (1.9m × 0.9m = 1.7m²), window (1.5m × 1m = 1.5m²). This prevents over-ordering. Enter your net wall area after subtracting openings for most accurate results.
Q: What is the difference between bonding and finishing plaster?
Bonding coat is the first coat (2-3mm) applied directly to brick or concrete blocks and uses around four times the quantity of a skim finish coat for the same area (1 × 25kg bag covers 2.5m² for bonding vs 10m² for finish). Finishing plaster (board finish or multi finish) is the final smooth top coat (about 2mm) providing the paintable surface. For plasterboard, you normally apply finish directly to the board.
Q: How does this compare to other trade calculators?
TradeCalcs offers a complete suite of professional estimators. For wood and labour costs, use our Joinery Calculator. For electrical compliance work, use our Voltage Drop Calculator. All tools are free and provide UK market rates with internal linking to help you build complete project estimates.
✓ Professional Quality Assurance
This calculator provides professional estimates based on UK industry standards. Standard coverage is 1 bag (25kg) per 10m² for finish plasters and per 2.5m² for bonding coats. Always account for waste and keep extra material for touch-ups and repairs. Follow manufacturer guidelines precisely and allow adequate curing time before finishing or painting.
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