Types of Plaster Explained: Which One Should You Use?

Understanding Plaster Types: Why It Matters

Walk into any builders’ merchant in Kent — whether it’s Travis Perkins, Wickes, or your local independent — and you’ll face bags of pink, grey, and white plaster with names like Thistle, Carlite, and Dri-Coat. For anyone new to plastering, it’s bewildering.

But here’s the truth: using the wrong plaster type is one of the most common mistakes in plastering, and it accounts for a significant proportion of the cracking, delamination, and adhesion failures we see on renovation jobs across Kent and the Southeast.

Modern gypsum plasters manufactured by British Gypsum are engineered products designed for specific substrates and applications. Understanding the differences isn’t just technical nitpicking — it’s essential for achieving a durable, professional finish that will last decades.

The Two Main Categories: Undercoats vs Finishing Plasters

Before we dive into specific products, you need to understand the fundamental distinction in plastering systems:

• Undercoat plasters (basecoats): Applied first to level uneven surfaces, typically 8-15mm thick, designed to key to the substrate
• Finishing plasters (skim coats): Applied over undercoats or directly to plasterboard, typically 2-3mm thick, creating the smooth surface you decorate

Most plastering jobs use both types in a two-coat system — unless you’re skimming directly over plasterboard, where you’d use only a finishing plaster. This distinction is covered in detail in our complete guide to plastering.

Undercoat Plasters: Bonding, Browning, and Hardwall

Bonding Plaster (Thistle Bond-It)

Bonding plaster is the workhorse of modern plastering — if you only learn one undercoat, make it this one. It’s a gypsum-based undercoat formulated for low-suction or non-porous backgrounds.

Best used on:

• Concrete blocks and dense concrete
• Plasterboard (when building up thickness)
• Painted surfaces (after proper preparation)
• Engineering bricks
• Expanded metal lath (EML)
• Surfaces treated with PVA or bonding agents

The key characteristic of bonding plaster is its excellent adhesion to smooth, low-suction surfaces where other plasters would simply slide off or fail to grip. It contains additives that improve its “stick” to difficult substrates.

Working characteristics:

• Setting time: 1.5-2 hours
• Coverage: One 25kg bag covers approximately 2.4-2.75m² at 12mm thickness
• Drying time: 5-7 days before applying finish coat (depending on ventilation and temperature)
• Colour: Pink/grey when wet, lighter when dry

As of 2026, expect to pay £8-£12 per 25kg bag from major suppliers, with Thistle Bond-It being the industry standard. Learn more about preparing surfaces in our guide to the first coat of plaster application.

Browning Plaster (Thistle Browning)

Browning plaster is the traditional undercoat for high-suction backgrounds — essentially, porous materials that suck moisture from plaster rapidly.

Best used on:

• Common bricks and clay bricks
• Medium-density concrete blocks
• Lightweight aggregate blocks
• Older lath and plaster (after preparation)

The difference between Browning and Bonding isn’t always obvious to DIYers, but it’s critical. Browning contains retarders that slow down the set, allowing the plaster to cure properly even when the substrate is pulling moisture out quickly. Use Bonding on high-suction brickwork, and you’ll find it sets too fast and doesn’t develop proper strength.

Working characteristics:

• Setting time: 1.5-2 hours
• Maximum thickness: 12mm per coat
• Drying time: 7-14 days before topcoat (longer than Bonding due to substrate absorption)
• Colour: Pink when wet

Hardwall Plaster (Thistle Hardwall)

Hardwall is a more recent innovation — essentially a faster-drying, higher-impact-resistance undercoat suitable for both medium and high-suction backgrounds. It’s become increasingly popular on new-build sites.

Advantages over traditional plasters:

• Dries in 2-3 days instead of 5-14 days
• Higher impact resistance when set (important for high-traffic areas)
• Can be used on most common backgrounds without switching products
• Better coverage — approximately 3.25m² per 25kg bag at 11mm

However, Hardwall is slightly more expensive (£10-£14 per bag) and can be less forgiving for beginners due to its faster set. Many professional plasterers still prefer the traditional Bonding/Browning approach because they know exactly how these products behave.

Finishing Plasters: Multi-Finish and Board Finish

Finishing plasters create the smooth, decorated surface. In the UK, you’ll primarily encounter two types from the British Gypsum Thistle range.

Multi-Finish Plaster (Thistle Multi-Finish)

Multi-Finish is the most versatile finishing plaster and the one you’ll see on virtually every domestic job. As the name suggests, it works on multiple backgrounds:

• Over Bonding, Browning, or Hardwall undercoats
• Directly onto plasterboard (though Board Finish is technically better)
• Over old painted plaster (properly prepared)
• Onto render (after appropriate preparation)

The beauty of Multi-Finish is its extended working time — you can polish it up beautifully with a wet trowel, achieving that glass-smooth finish clients expect. It’s formulated to handle varying suction rates, which makes it forgiving on patchy surfaces.

Application specifications:

• Thickness: 2mm minimum, 3mm optimum
• Setting time: 1.5-2 hours
• Coverage: 8.4-10.25m² per 25kg bag (at 2-3mm)
• Drying time: 3-7 days before painting (learn more in our guide on how long to leave plaster before painting)

For more details on achieving professional results with this product, see our article on what is finishing plaster and when to use it.

Board Finish Plaster (Thistle Board Finish)

Board Finish is specifically formulated for direct application to plasterboard and low-suction backgrounds. It’s lighter in weight and has different working properties compared to Multi-Finish.

When to use Board Finish instead of Multi-Finish:

• New plasterboard installations
• Tapered-edge boards requiring thin skim coats
• Large areas of board where you want faster drying
• Situations requiring lighter weight (ceiling work)

Many plasterers use Multi-Finish for everything because it’s more versatile and they’re comfortable with it. However, Board Finish technically performs better on plasterboard — it’s designed for the job. It sets slightly harder and has better resistance to picture hook damage.

Coverage is similar to Multi-Finish (around 9.3m² per 25kg bag at 2mm), and pricing is comparable at £9-£13 per bag in 2026.

Specialist Plasters for Specific Applications

One-Coat Plaster (Thistle Universal One Coat)

One-coat plasters can be applied in thicknesses from 5mm to 50mm in a single application, eliminating the traditional two-coat system. They’re popular for:

• Patch repairs where you need varying depths
• Small jobs where setting up for two coats isn’t economical
• Utility areas where appearance isn’t critical

However, professional plasterers rarely use one-coat systems for whole rooms. The finish quality doesn’t match a proper two-coat system, and they’re more expensive per square metre (£12-£16 per 25kg bag).

Dri-Coat and Renovating Plasters

When dealing with damp-affected walls, standard gypsum plasters aren’t suitable. Dri-Coat is a cement-based renovating plaster containing water-repellent additives and designed to allow moisture vapour transmission while blocking liquid water.

According to Building Regulations Approved Document C, proper damp-proofing is essential before plastering. Dri-Coat is typically applied in two coats to 25mm total thickness.

For comprehensive information on this specialist material, see our guide to damp proof plaster systems.

Magnetic Plaster and Decorative Options

Modern plasters extend beyond basic finishing:

• Magnetic plaster: Contains iron particles allowing magnets to stick — popular in children’s rooms and offices
• Insulating plaster: Thermally enhanced plasters improving U-values (covered in our insulating plaster guide)
• Acoustic plaster: Sound-absorbing formulations for studios and home cinemas
• Lime plaster: Traditional breathable plaster for heritage buildings and period properties

Choosing the Right Plaster: Decision Framework

Here’s a practical decision tree for selecting plaster types:

Step 1: Identify Your Substrate

Low-suction backgrounds: Concrete, dense blocks, painted surfaces, plasterboard with PVA

• Undercoat: Bonding Plaster
• Finish: Multi-Finish or Board Finish

High-suction backgrounds: Common brick, lightweight blocks, clay bricks

• Undercoat: Browning Plaster
• Finish: Multi-Finish

Mixed or uncertain backgrounds:

• Undercoat: Hardwall (versatile option)
• Finish: Multi-Finish

Step 2: Consider Your Timeline

Need to paint quickly? Hardwall undercoat dries in 2-3 days compared to 7-14 days for traditional plasters. However, proper curing always produces better results than rushing the job.

Step 3: Assess Thickness Requirements

The maximum safe thickness varies by plaster type:

Common Plaster Selection Mistakes

After 15+ years plastering across Kent, these are the mistakes we see most often:

1. Using Multi-Finish as an undercoat: It’s a finishing plaster designed for 2-3mm application. Applied thicker, it cracks and lacks strength. If you need depth, use a proper undercoat.

2. Bonding onto high-suction bricks: The brick sucks moisture out too fast, the plaster sets before it can key properly, and you get poor adhesion. Use Browning or seal the brickwork first with diluted PVA (though this changes it to a low-suction background).

3. Applying finish coat too soon: Rush the job and apply Multi-Finish over damp Bonding, and you’ll see cracks appear within weeks as the undercoat continues to dry and shrink.

4. Wrong mixing ratios: Gypsum plasters are factory-formulated. Adding extra water to make them easier to spread weakens the final product significantly. Always follow manufacturer specifications — typically around 11.5 litres per 25kg bag for most Thistle products.

5. Not matching substrate preparation to plaster type: Each plaster type has specific suction requirements. PVA sealing, water dampening, or bonding agents might be necessary depending on your substrate-plaster combination.

Storage and Shelf Life

Gypsum plasters deteriorate over time, especially in damp conditions. Proper storage is critical:

• Store bags off the ground on pallets
• Keep in dry, weatherproof conditions
• Use oldest stock first (rotate inventory)
• Shelf life: 3-4 months unopened in good conditions, use immediately once opened

You can tell plaster has deteriorated when it contains hard lumps, sets too quickly (often within 20-30 minutes), or produces a weak, crumbly finish. At current prices, it’s false economy to use degraded plaster — bin it and start fresh.

Environmental and Health Considerations

Modern gypsum plasters are generally safe materials, but proper handling is essential:

• Dust hazards: Gypsum dust irritates eyes and respiratory system. Always wear a dust mask when mixing, especially in enclosed spaces
• Skin contact: Prolonged contact causes skin drying and irritation. Wear gloves or use barrier cream
• Disposal: Set plaster can go in general waste, but liquid plaster must never go down drains — it sets solid and blocks pipework
• Environmental impact: British Gypsum operates to ISO 14001 environmental standards, with significant recycled content in most products

Cost Comparison: Material Pricing 2026

Here’s what you can expect to pay at UK builders’ merchants (prices vary by supplier and location):

Prices typically drop 10-15% when buying in bulk (full pallets) from trade suppliers. For comprehensive pricing information including labour, see our guide on plastering costs in Kent.

Professional Tips for Working with Different Plaster Types

Mixing technique matters: Always add plaster to water, never water to plaster. This prevents lumps and ensures proper consistency. For a 25kg bag of Multi-Finish, use a 30-litre mixing bucket with approximately 11.5 litres of clean water.

Testing suction: Before choosing between Bonding and Browning, test your substrate. Spray water on the surface — if it soaks in within seconds, you have high suction (use Browning). If it sits on the surface, you have low suction (use Bonding).

Temperature control: Plaster sets faster in warm conditions, slower in cold. Below 5°C, don’t plaster at all without heating — the set won’t develop properly. Above 30°C, work in smaller batches as setting time reduces significantly.

Keying surfaces: For Bonding or Browning undercoats, scratch the surface horizontally with a scarifier or devil float before it sets. This provides mechanical key for the finish coat. For finishing plasters, the smooth trowelled surface is what you want.

Frequently Asked Questions

Can I use Multi-Finish directly on bare brick or blockwork?

Technically yes, but it’s not recommended for anything except small patch repairs. Multi-Finish is designed as a finishing plaster 2-3mm thick. On uneven masonry, you need an undercoat (Bonding or Browning) to level the surface first, then Multi-Finish provides the smooth decorated surface. Trying to use Multi-Finish to fill hollows and level walls leads to cracking and delamination because it’s applied too thick in some areas.

What’s the difference between Bonding and Browning — can’t I just use one for everything?

The key difference is suction management. Browning is formulated for high-suction backgrounds (porous bricks, blocks) — it contains retarders that slow the set, allowing proper curing even when the substrate is pulling moisture out rapidly. Bonding is designed for low-suction backgrounds (concrete, painted surfaces) where adhesion is the challenge rather than suction. Using Bonding on high-suction brick means it sets too fast and doesn’t develop proper strength. Using Browning on low-suction concrete gives poor adhesion. Match the plaster to the substrate for best results.

How long do I really need to wait before skimming over Bonding?

The rule of thumb is 5-7 days for Bonding in good drying conditions (well-ventilated, 15-20°C), or 7-14 days for Browning. You’re waiting for the undercoat to dry sufficiently that it won’t shrink further after the finish coat is applied. You can test readiness by pressing firmly on the undercoat surface — it should feel solid with no give, and uniform in colour (lighter pink or grey, not dark patches). In winter or poorly ventilated spaces, double these times. The finish coat drying time is separate — allow another 3-7 days before painting.

Is it worth buying Hardwall instead of Bonding and Browning?

Hardwall is marketed as a universal undercoat suitable for most backgrounds, and it does offer faster drying (2-3 days vs 5-14 days). For small jobs or if you’re unsure about substrate suction, it’s a safe choice. However, many professional plasterers stick with Bonding and Browning because they know exactly how these materials behave in different conditions. Hardwall is also slightly more expensive and can be less forgiving for beginners. If you’re doing large-scale work, the traditional approach with separate products typically gives better results. For occasional DIY work, Hardwall’s versatility might be worth the extra cost.

Can I mix different brands of plaster — Thistle with Knauf or Gyproc?

While most gypsum plasters from reputable manufacturers have similar formulations, mixing brands in the same coat isn’t recommended. Different manufacturers use slightly different additives, setting rates, and working properties. For best results, stick with one brand throughout the job. British Gypsum’s Thistle range is the industry standard in the UK, with the widest availability and most comprehensive technical support. That said, if you need to patch over existing plaster from a different brand, ensure the surface is properly prepared and use appropriate bonding agents if necessary.

Why does my plaster crack even when I use the right type?

Using the correct plaster type is necessary but not sufficient for crack-free results. Common causes of cracking include: applying finish coat over damp undercoat, excessive thickness in one coat, poor substrate preparation, movement in the building structure, rapid drying (forced heating), incorrect mixing ratios (too much water), and painting before plaster is fully dry. Even with perfect technique, hairline cracking can occur at internal angles due to thermal expansion/contraction — this is normal and addressed during decoration. For persistent cracking issues, see our article on why plaster cracks and prevention methods.