How to tape and joint plasterboard

Video by Tommy's Trade Secrets. This walk-through is based on the video "Tommy's Trade Secrets - How To Tape And Joint A Plasterboard Wall" from Tommy's Trade Secrets, which covers the full process from first coat through to a paint-ready finish. Well worth a watch before you buy your materials — it gives a clear sense of how thin each coat needs to be and how much drying time to allow between them.

1. Use tapered-edge board and gather the right materials

Taping and jointing only works properly on tapered-edge plasterboard — the kind where the long edges have a shallow recess along them. That recess is where the tape beds in and where the jointing compound builds up flush with the surrounding board face. Square-edge board, which is designed for plastering over, does not have this and will leave you with a visible ridge however carefully you work.

You will need jointing compound (sometimes called joint filler or ready-mixed compound), paper jointing tape, a 150 mm and a 250 mm jointing knife, a mud pan or hawk, and fine sandpaper or a sanding sponge. Ready-mixed compound from a tub is easiest for most DIYers — it does not set as fast as powder compound and you have time to correct mistakes. That said, it takes longer to dry between coats, so factor in a full day between each one.

2. Fill screw dimples with a first coat

Before you touch the joints, run compound over every screw head first. Load a small amount onto the 150 mm knife and draw it firmly across each dimple to leave a thin, slightly proud fill. Do not try to get them perfectly flat on this first pass — you just want the holes filled and the compound pressed in properly. Come back to them once the first coat is dry.

Work methodically across the whole surface, doing all the screw dimples in one go rather than hopping between joints and fixings. It keeps things tidy and means you are not constantly going back with a wet knife to a surface that has already started to skin over.

3. Apply the first coat of compound to the joints

Load the 150 mm knife with compound and spread a thin, even layer along the tapered joint — about 100 mm wide, just enough to bed the tape into. Immediately press a length of paper tape over the joint, centred on it, and use the knife to bed it firmly into the compound. Work from the middle outwards to avoid trapping air bubbles under the tape.

Once the tape is bedded, apply a thin skim coat of compound over the top of it and feather the edges out slightly. You are not trying to fill the joint flush at this stage — just getting the tape flat and embedded. Any compound that squeezes out from under the tape can be smoothed back over the joint with the knife. Leave it to dry completely before the next coat.

4. Apply the second (fill) coat with a wider knife

Switch to the 250 mm jointing knife for the second coat. This is the coat that starts to bring the joint up flush with the board face. Apply a thin, even layer of compound across the full width of the tapered recess, feathering it out 50 mm or so beyond the edges of the first coat. The wider the feather, the less visible the joint will be under a raking light.

The golden rule with jointing compound is always thin coats. If you try to fill the joint in one thick coat it will shrink and crack as it dries. Two or three thin coats, each sanded lightly when dry, always beats one thick one. Go back over the screw dimples with this coat too, and feather them out so they start to disappear into the surrounding board.

5. Sand between coats and apply the finish coat

Once the second coat is bone dry, sand it lightly with 120-grit sandpaper or a fine sanding sponge. You are just knocking back any ridges or knife marks — you do not need to remove much material. Wipe the dust away with a barely damp cloth and let the surface dry out again before the next coat.

The third (finish) coat is the thinnest of all — more like a skim than a fill. Use a very light touch and a clean knife. You want to blend the joint invisibly into the board surface with a wide, flat pass. If you can still see the tape through the compound, apply a fourth coat. It depends on the conditions and how even your earlier coats were, but three coats is typical on a tapered joint in a normal room.

6. Final sand, prime, and check under a raking light

Once the finish coat is fully dry, give the whole surface a final sand with 120–150 grit. Work across the joints with long, even strokes rather than scrubbing in circles, which tends to leave swirl marks. Pay particular attention to the edges of the feathered area, which can dry with a slight lip if the compound was applied unevenly.

Before painting, prime the whole surface with a proper drywall primer or a diluted coat of emulsion mixed 50:50 with water. This seals the board and the compound evenly so the finish paint does not show up patches. To check your work, hold a torch or work light at a very low angle (raking light) across the surface — any hollows, ridges, or imperfections will show up clearly now rather than after you have painted. Much better to fix them at this stage than repaint the whole wall.

When to call a handyman

Call Richard if you have a large area of newly boarded walls or ceilings to finish, if previous taping has cracked and needs stripping back, or if you simply want the job done without having to learn a new skill and wait three days between coats. Getting the surface perfectly flat for a smooth paint finish takes a bit of practice, and Richard has done enough of it to know where the common mistakes happen. Give him a call if you are in Sandwich or the wider East Kent area.