How to fit corner beads to plaster and plasterboard

Inspired by a helpful YouTube guide. This walk-through draws on the popular UK video "How To Fit Corner Beads To Plaster And Plasterboard", which covers both the fixing method and the plastering technique to get a clean, finished corner.

1. Choose the right type of corner bead

There are three main types: galvanised metal bead, plastic bead (also called uPVC or PVC bead), and paper-faced bead. Metal bead is the traditional choice for sand-and-cement render and browning plaster coats. Plastic bead is better in areas prone to movement, such as around windows, because it flexes slightly without cracking the plaster. Paper-faced bead is designed for plasterboard finishing - it beds into joint compound rather than bonding plaster.

For a standard internal plastered corner, galvanised metal or plastic bead fixed with bonding plaster is the most common approach. Check that the bead nose (the small round bump at the corner) is not too large for the plaster depth you are applying - standard 10 mm nose suits most situations.

2. Measure and cut the bead to length

Measure the height of the corner you are working on. Cut metal bead with tin snips or an angle grinder with a thin cutting disc. Cut plastic bead with a sharp craft knife or a hacksaw. Always cut square - a bead that is slightly off-square will rock and be difficult to set plumb.

If you are running bead from floor to ceiling, cut it 2 mm short at each end so it does not butt hard into the floor screed or ceiling. This small gap allows for movement and makes it easier to get a clean finish at the joints.

3. Fix the bead with dabs of bonding plaster

Mix up a small amount of bonding plaster - just enough to work with for 20 minutes. Apply four or five golf-ball-sized dabs down each wing of the bead. Press the bead firmly onto the corner, pushing the dabs into good contact with the wall behind.

Do not try to use the bead as a float guide at this stage - just get it roughly in position. Hold it with one hand while you adjust and check alignment. The plaster dabs set slowly enough that you have a few minutes to make corrections.

4. Check for plumb and straightness

This is the step that matters most. Hold a spirit level against the bead nose and check it is plumb in both directions. Look along the bead from floor level to check there are no bows - a bead with a slight curve in it will show in the finished wall.

Press gently at any high points to bed them in further. If one area is too far in, carefully lever the bead out slightly and add more plaster behind. Take your time. Once the dabs harden, the bead is set where it is. Checking now costs two minutes. Fixing a crooked bead after the plaster is on costs considerably more.

5. Allow the fixing dabs to set before plastering

Leave the bead for at least 30 minutes - ideally an hour - so the fixing dabs firm up. If you plaster straight away, the bead can shift as you apply pressure with the float. A firmly set bead makes the whole plastering job cleaner and easier.

While you are waiting, dampen down the wall behind so the surface is evenly absorbent. A bone-dry background will pull moisture out of the plaster too quickly and make it hard to work. A surface that is too wet will cause the plaster to slip down. Slightly damp is right.

6. Apply the plaster coat and rule off against the bead

Apply bonding plaster to each face of the wall beside the bead, working from the bead outwards. Flatten the plaster with a straight edge (a feather-edge rule or a long plasterer's darby) using the bead nose as one edge of your guide. Pull the rule along the surface in a sawing motion to level the plaster flush with the bead.

Fill any low spots you find, rule off again, and leave to set. When the browning coat is firm enough to resist a thumbnail but not fully hard, scratch the surface with a nail float or a comb scratcher to provide a key for the finish coat.

7. Apply the finish coat and polish up

Mix finish plaster (multi-finish or board finish depending on the background) to a creamy, lump-free consistency. Apply a thin coat over the scratched browning, again using the bead nose as a guide. Two thin coats are better than one thick one. Work the surface with a clean wet steel float as it starts to stiffen, using tight circular strokes to close the surface and bring up a smooth finish.

Flick water lightly onto any areas that are drying too fast. The corner itself should be sharp and crisp where the bead nose sits proud by just a fraction of a millimetre. Once fully set, any slight irregularities at the bead edge can be rubbed down lightly with fine sandpaper before painting.

When to call a handyman

Fitting corner bead is straightforward enough if you are comfortable with basic plastering. If you are patching a corner that keeps getting damaged, need bead running on multiple doorways, or want a full room replastered with proper protection on every edge, call Richard. It is the sort of job that takes a lot longer than it looks when you are doing it for the first time.