How many bags of plaster do I need?

A 25kg bag of multi-finish plaster (such as Thistle Multi-Finish) covers approximately 7.5-8.5 m² at 2mm skim thickness. For a typical bedroom (approximately 35 m² of wall area), you need 4-5 bags of multi-finish. A 25kg bag of bonding coat covers about 2.5-3.5 m² at 8mm thickness. Use our calculator for an exact figure based on your room dimensions.

What is the difference between bonding coat and multi-finish plaster?

Bonding coat is an undercoat plaster applied directly to bare brickwork, concrete or other rough surfaces at 8-11mm thickness. It provides a flat, keyed surface for the finish coat. Multi-finish (such as Thistle Multi-Finish) is a top-coat plaster applied over bonding coat or existing plaster at 2-3mm thickness to create a smooth, paintable surface. Most replastering jobs require both layers.

How much does it cost to plaster a room in the UK?

For a typical bedroom, materials cost approximately £50-£80 for plaster alone. If hiring a plasterer, expect to pay £400-£700 for a small room (skimming only) or £800-£1,500 for full replaster including bonding coat. Labour rates vary by region — London and the South East are typically 20-30% higher than the Midlands and North.

How long does plaster take to dry?

Bonding coat sets in approximately 1.5-2 hours and is ready for the finish coat after about 2 hours. Multi-finish plaster sets in about 1.5 hours. However, the plaster must fully dry before painting, which takes 2-4 weeks in average UK conditions depending on ventilation, heating and humidity. The plaster changes from dark to light pink/white as it dries.

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Complete Guide to Plastering in the UK

Plastering is one of the most skill-intensive DIY tasks, but understanding material quantities is the essential first step whether you are doing the work yourself or getting quotes from professionals. This guide covers everything you need to know about plaster types, coverage rates and costs in the UK.

Types of Plaster Available in the UK

The UK plastering market is dominated by British Gypsum's Thistle range, which accounts for the vast majority of plaster sold through builders' merchants. Here are the main types and their applications:

Plaster Type	Thickness	Coverage (per 25kg bag)	Price per Bag	Application
Thistle Multi-Finish	2mm	7.5-8.5 m²	£8-£12	Top coat over any background
Thistle Board Finish	2mm	8.5-9.5 m²	£7-£10	Top coat on plasterboard only
Thistle Bonding Coat	8mm	2.5-3.5 m²	£7-£10	Undercoat on low-suction surfaces
Thistle Hardwall	11mm	2-3 m²	£7-£10	Undercoat on high-suction surfaces
Thistle Browning	8mm	3-3.5 m²	£7-£10	Undercoat on absorbent backgrounds
One-Coat Plaster	13mm	1.8-2.2 m²	£8-£12	Single-coat application on any surface
Exterior Render	15-20mm	1.5-2 m²	£8-£14	External walls

Skimming vs Full Replaster

Understanding the difference between skimming and full replastering determines which plasters you need and how much to order:

Skimming (re-skimming) involves applying a thin 2-3mm top coat of multi-finish or board finish plaster over an existing surface. This is appropriate when the existing plaster is still solid and well-bonded but has a poor surface finish (bumps, cracks, textured coatings like Artex). Skimming is the most common plastering job in UK homes and typically requires only multi-finish plaster.

Full replaster involves removing the old plaster back to bare brick or block, applying PVA or bonding agent, then a bonding coat or hardwall undercoat, and finally a multi-finish top coat. This is necessary when existing plaster is blown (hollow-sounding when tapped), damp-damaged or otherwise failing. A full replaster requires both undercoat and finish coat plasters.

Test your plaster: Tap the walls with your knuckles. Solid plaster produces a dull thud; blown plaster sounds hollow. If more than 25% of the wall sounds hollow, a full replaster is generally more cost-effective than patching.

Plaster Drying and Setting Times

Understanding plaster drying times is crucial for scheduling work and avoiding costly mistakes:

Bonding coat setting time: 1.5-2 hours. The surface should be scratched with a devilling float to create a key for the top coat while still wet.
Multi-finish setting time: Approximately 1.5 hours. This is the working time available to apply and trowel up to a smooth finish.
Drying time before painting: 2-4 weeks in average UK conditions. The plaster transitions from dark pink/brown to a uniform pale pink or white when fully dry. Do NOT paint until fully dry — trapped moisture causes paint failure.
First coat of paint: Always apply a mist coat (diluted emulsion or dedicated plaster primer) as the first coat on new plaster. This seals the surface without creating a film that prevents further drying.

Plastering Costs per Square Metre in the UK (2026)

If hiring a professional plasterer, expect the following rates. These include labour and materials:

Job Type	Cost per m²	Typical Room Cost
Skim coat (over existing plaster)	£12-£20	£400-£700
Full replaster (to bare wall)	£20-£35	£800-£1,500
Ceiling skim	£15-£25	£200-£400
Plasterboard + skim	£25-£40	£1,000-£1,800
Artex removal + skim	£18-£30	£250-£500 (ceiling)

Labour rates vary significantly by region. London and the South East typically charge 20-30% more than the national average. Northern England, Wales and Scotland tend to be at the lower end of the range. Always get at least three quotes from local plasterers.

DIY Plastering Tips

If you are attempting plastering as a DIY project, here are essential tips for a better result:

Prepare the surface properly: Remove loose material, fill large holes with bonding coat, and apply PVA (diluted 1:5 with water) to seal the surface. PVA provides suction control and bonding.
Mix correctly: Always add plaster to water, never water to plaster. The consistency should be like thick cream — firm enough to stay on the hawk without sliding off. Mix only what you can apply in 20-30 minutes.
Work in manageable sections: Apply plaster to one wall at a time. Do not try to do an entire room at once.
Two-coat application: Apply a thin first coat (1mm), let it firm up for 10-15 minutes, then apply the second coat (1mm) and trowel to a smooth finish.
Trowel technique: Apply firm pressure at a slight angle. Work from bottom to top, then smooth from top to bottom. Final passes should be with a very wet trowel for maximum smoothness.
Clean tools immediately: Plaster sets on tools just as it sets on walls. Wash all tools in clean water as soon as you finish.

Where to Buy Plaster in the UK

Wickes and B&Q stock the full Thistle range at retail prices. Jewson and Travis Perkins offer trade pricing (typically 10-20% cheaper) and are open to the public. For large quantities, ask about pallet pricing — a pallet of 56 bags of multi-finish from a builders' merchant can be significantly cheaper per bag than buying individually.

Storage warning: Plaster must be stored in a dry environment and used within 6 months of purchase. Damp or old plaster sets too quickly and produces a weak, crumbly finish. Never use plaster that has hard lumps in the bag — it has already begun to set and will not perform correctly.

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