Plasterboard Jointing: UK Guide

Why joint plasterboard?

When plasterboard sheets meet, the joint between them creates a visible line and a potential weak point. Jointing (also called taping and filling) reinforces the joint and creates a smooth, invisible finish. Done correctly, the wall looks like a continuous surface with no visible seams.

Tapered-edge boards have a shallow recess along the long edges. When two boards meet, the tapers form a channel. You fill this with compound and tape, then feather it level with the surrounding board. The result is flush and invisible.

Square-edge boards have no taper. Joints are proud (raised) unless you skim the whole surface with plaster. Jointing square-edge boards is possible but the joint is harder to hide. Use tapered-edge if you plan to decorate directly without skimming.

Paper tape vs mesh tape

Paper tape (recommended)

Traditional method. Paper tape is stronger, less prone to cracking, and creates a flatter finish. It requires a thin bed of jointing compound under the tape to adhere. Slightly harder to apply but professional results. Use for all tapered joints and internal corners. Costs £3-5 per 150m roll.

Mesh tape (self-adhesive)

Fibreglass mesh with adhesive backing. Press it onto the joint without compound underneath. Easier for beginners. Weaker than paper tape and more prone to showing through paint if not feathered properly. Useful for repairs or small jobs. Avoid for whole-room new builds. Costs £5-8 per 50m roll.

Which to use?

Paper tape for new builds and professional finish. Mesh tape for quick repairs or if you are inexperienced and want an easier starting point. Once you learn the technique, paper tape is better in every way.

Jointing compound vs filler

Jointing compound (recommended for taping)

Fine powder mixed with water to a creamy consistency. Designed for feathering out to thin edges. Dries slowly (4-24 hours depending on coat thickness). Easy to sand. Use for taping joints and creating smooth finishes. Common brands: Gyproc Easi-Fill, Knauf Joint Filler, Toupret TX110. Costs £8-12 per 10kg bag.

Ready-mixed compound

Pre-mixed jointing compound in tubs. No mixing required. More expensive per m² but convenient for small jobs. Slightly harder to feather than powder compound. Dries slower. Use for repairs or small areas. Costs £12-18 per 12L tub.

General-purpose filler

Not suitable for taping joints. Too coarse and prone to cracking over wide areas. Use filler for screw holes and small defects, not for joint reinforcement.

Step-by-step jointing technique

Preparation

Ensure all boards are securely fixed with screws just below the surface (not protruding). Brush dust from joints. Check the taper is clean and free of damaged paper. Mix jointing compound to a smooth, creamy consistency (like thick yogurt).

First coat: embed the tape

Apply a thin layer of compound into the tapered channel using a 150mm jointing knife. Press paper tape into the wet compound, centred on the joint. Run the knife along the tape with firm pressure to embed it and squeeze out excess compound. The tape should be fully bedded with a thin layer of compound visible through it. Let it dry (4-6 hours minimum, overnight is better).

Second coat: fill and level

Apply a wider layer of compound (200-250mm wide) using a 250mm jointing knife. Fill the taper flush with the surrounding board. Feather the edges by reducing pressure as you move away from the joint. Let it dry fully (12-24 hours). The compound shrinks slightly as it dries, so the joint may still be slightly visible.

Third coat: feather and finish

Apply a final thin coat (300-400mm wide) using a 300mm trowel or jointing knife. Feather the edges to create a gradual transition to the board surface. Use very light pressure and skim off excess. The coat should be almost invisible at the edges. Let it dry fully (12-24 hours).

Sanding

Lightly sand with 120-grit paper on a sanding block or pole sander. Remove any ridges or high spots. Do not sand through to the tape. Wipe dust off with a damp cloth. Prime before painting or the compound will show as a different sheen.

Internal corners

Internal corners (where two walls meet or wall meets ceiling) require a different technique. Fold paper tape in half lengthwise to create a crease, then embed it into the corner with compound. Alternatively, use a corner trowel to apply compound and tape in one motion.

Apply compound to both sides of the corner, press the folded tape into the angle, then smooth each side with a jointing knife. Feather the edges as with flat joints. Internal corners often need only two coats if done carefully.

External corners

External corners (wall edges, window reveals) are reinforced with metal or plastic corner bead, not tape. Nail or screw the bead to the corner, then apply compound over it in two or three coats, feathering out to 150-200mm each side. The bead provides a sharp, durable edge that resists damage.

Metal bead is stronger but can rust if exposed to moisture. Plastic bead is rust-proof and easier to cut but less impact-resistant. For most domestic use, plastic bead is fine.

Common problems and solutions

Tape bubbling or lifting

Caused by insufficient compound under the tape or air trapped during embedding. Press the tape firmly into wet compound and squeegee out air bubbles. If the tape lifts after drying, cut it out and re-tape.

Cracking along the joint

Usually caused by movement in the building (settlement, thermal expansion) or using mesh tape without enough compound. Paper tape is stronger and less prone to cracking. Ensure boards are securely fixed and not flexing. For persistent cracks, use flexible filler or consider skimming the whole surface.

Ridges or visible edges

Compound not feathered wide enough or too thick. Each coat should be wider than the previous one and feathered to almost nothing at the edges. Use a wider knife and lighter pressure. Sand any ridges before the next coat.

Compound not drying

Poor ventilation or very thick application. Open windows, use a dehumidifier, or wait longer. Thick coats can take 48 hours to dry. Avoid forced drying with heaters which can cause cracking.

Screw heads and fixings

Screw heads must be just below the board surface (countersunk). Fill each screw hole with jointing compound using a filling knife. Apply compound, scrape off excess, let it dry, then apply a second thin coat if needed. Sand lightly when dry.

Overdriven screws (broken through the paper face) have no holding power. Remove and replace them 50mm away. Fill the damaged hole with filler.

Priming before decoration

Jointing compound is more absorbent than plasterboard paper. If you paint directly without priming, the joints show as dull patches. Apply a mist coat (diluted emulsion, 10-20% water) or a purpose-made plasterboard primer. This seals the compound and ensures even sheen when you apply the topcoat.

For wallpaper, use wallpaper size or diluted paste to seal the surface. This prevents the paste over-soaking into the compound and allows you to reposition the paper.

Cost and time

Materials for a typical room (40m² of board, around 30m of joints):

• Jointing compound: 2-3 bags (20-30kg), £20-35
• Paper tape: 1 roll (150m), £4-6
• Sandpaper and primer: £10-15
• Total material cost: £35-55

Time: 1-2 hours to apply first coat, 1-2 hours for second coat, 1 hour for third coat, 1 hour sanding and priming. Plus 2-3 days drying time between coats. Total elapsed time: 3-4 days. Rush the drying and you risk cracking or poor adhesion.

Hiring a professional taper costs £150-300 for a standard room, including materials and labour. They will complete it faster (often two coats only, using setting-type compound that dries in hours) and to a higher standard.

Related guides

• Plasterboard: Complete Guide
• Plasterboard Sizes UK
• How to Plaster a Wall: UK Guide
• Finishing Plaster Explained