Multi Finish vs Board Finish vs Bonding Plaster: Which Do You Need?
Thistle MultiFinish, BoardFinish, BondingCoat and HardWall are the four British Gypsum plasters we're asked about most, and picking the wrong one is a common cause of cracking, poor adhesion and wasted bags. The short version is that finish plasters go on last in a thin coat, undercoats build up and level the wall first, and the background you're plastering onto decides which one you need. This guide compares them using British Gypsum's product data sheets.
Quick answer
- Skimming plasterboard? Use MultiFinish or BoardFinish, 2mm thick.
- Finishing over a HardWall or other undercoat? Use MultiFinish. It suits both low-suction backgrounds and medium-to-high-suction undercoats.
- Undercoat on bricks or aircrete blocks (medium to high suction)? Use HardWall.
- Undercoat on smooth or low-suction backgrounds such as engineering brick, dense concrete, plasterboard, metal lath or surfaces treated with a bonding agent? Use BondingCoat.
Side-by-side comparison
From British Gypsum's product data sheets. Prices are per 25kg bag, ex VAT, at the time of writing:
| MultiFinish | BoardFinish | BondingCoat | HardWall | |
|---|---|---|---|---|
| Type | Finish coat | Finish coat | Undercoat | Undercoat |
| Backgrounds | Low suction (plasterboard, flat concrete, bonding-agent-treated surfaces) and medium–high suction undercoats | Low suction (plasterboard, Thistle DriCoat, flat concrete, bonding-agent-treated surfaces) | Smooth or low suction (some brick, block and concrete, plasterboard, expanded metal lath, bonding-agent-treated surfaces) | Medium to high suction masonry, such as bricks and aircrete blocks |
| Application thickness | 2mm (walls and ceilings) | 2mm (walls and ceilings) | 11mm walls, 8mm ceilings | 11mm walls, 8mm ceilings |
| Coverage per 25kg bag | 10m² at 2mm | 10m² at 2mm | 2.75m² at 11mm (3.5m² at 8mm) | 3m² at 11mm |
| Working time (max) | 40 minutes | 40 minutes | 80 minutes | 80 minutes |
| Set time (min) | 90 minutes | 90 minutes | 200 minutes | 120 minutes |
| Reaction to fire | A1 | A1 | A1 | A1 |
| Shelf life | 4 months | 4 months | 4 months | 4 months |
| Price per bag | £8.54 | £9.99 | £12.52 | £15.34 |
| Approx. cost per m² at the stated coverage | £0.85 | £1.00 | £4.55 (at 11mm) | £5.11 (at 11mm) |
MultiFinish vs BoardFinish
Both are 2mm gypsum finish plasters, with the same coverage, working time and set time. The difference is the backgrounds British Gypsum lists:
- BoardFinish is for low-suction backgrounds: plasterboard, Thistle DriCoat, flat concrete and surfaces treated with a bonding agent.
- MultiFinish covers the same low-suction backgrounds and is also suitable over medium-to-high-suction gypsum or cement-based undercoats. It's the finish British Gypsum names for use over HardWall.
If you only ever skim plasterboard, either will do. If you're finishing a mix of new plasterboard and undercoated walls, MultiFinish lets you use one bag type for both. Our MultiFinish guide has more on working with it.
BondingCoat vs HardWall
Both are undercoats, applied up to 11mm on walls and 8mm on ceilings, scratched to give a key and then finished with 2mm of finish plaster. Choose by suction:
- HardWall is for medium to high suction backgrounds, such as common bricks and aircrete blocks. Aircrete may need Thistle GypPrime first to control suction.
- BondingCoat is for smooth or low-suction backgrounds, such as engineering bricks, dense concrete blocks, concrete, plasterboard, expanded metal lath and surfaces treated with a bonding agent.
A quick test: flick a little water on the wall. If it soaks in quickly, the background has high suction (think HardWall). If it runs off or sits on the surface, it has low suction (think BondingCoat, possibly with a bonding agent).
How a two-coat job goes together
- Prepare the background. Remove dust and loose material and control suction as the data sheet advises. Don't plaster onto frozen backgrounds.
- Undercoat. Apply HardWall or BondingCoat, building out without exceeding the stated thickness per coat. Rule it flat and lightly scratch it to form a key.
- Finish. Apply 2mm of MultiFinish, usually in two thin applications, and trowel it smooth as it sets.
- Angles and joints. On plasterboard, reinforce joints with scrim tape and fit thin-coat angle beads to external corners before skimming. See our beads, tapes and fillers.
- Let it dry thoroughly before decorating. British Gypsum says you can apply a coat of permeable paint in the meantime.
Buying tips
- Work out bags from coverage. For 2mm of finish over 30m² of plasterboard, 30 ÷ 10 = 3 bags. Add one spare.
- Watch the shelf life. British Gypsum gives four months, and bags are marked with a use-by date. Buy for the job in hand rather than stockpiling.
- Store bags indoors, flat and dry, and raised off concrete floors.
- Tiling: according to the data sheets, you can tile up to 20kg per m² directly onto Thistle finish plasters, except where the system includes a bonding agent.
Frequently asked questions
Can I use MultiFinish on plasterboard?
Yes. Plasterboard is one of the low-suction backgrounds British Gypsum lists for MultiFinish, applied 2mm thick.
Can I put BoardFinish over HardWall?
British Gypsum lists BoardFinish for low-suction backgrounds, and names MultiFinish as a finish for HardWall. Use MultiFinish over HardWall.
How much does one bag of MultiFinish cover?
About 10m² at 2mm thick, according to British Gypsum.
How long does MultiFinish take to set?
British Gypsum gives a maximum working time of 40 minutes and a minimum set time of 90 minutes. Drying before decoration takes longer, depending on conditions.
Do I need plaster on insulated plasterboard?
You can tape and fill the joints or skim it with a finish plaster, the same as standard board. See our guide on how to install insulated plasterboard.
Order plaster
Browse our British Gypsum plaster and adhesive range, including Gyproc DriWall Adhesive for dot-and-dab (£9.49 per 25kg bag at the time of writing), and see our guide to plasterboard sizes. Prices are shown ex VAT. We are delivery only (no collection) and deliver to mainland England and Wales, with a £400 ex VAT minimum order and free delivery on every order (see delivery information). Call us on 03330 908479 (Mon–Thu 8am–5pm, Fri 8am–12pm), email sales@insulationwarehousedirect.co.uk, or order online.
Sources: British Gypsum product data sheets for Thistle MultiFinish, Thistle BoardFinish, Thistle BondingCoat and Thistle HardWall. Figures are indicative and correct at the time of writing.