How thick is plaster? Layer thickness by finish

How thick is plaster for each type of finish?

There is no single thickness for plaster. The substrate, and what goes on the wall afterwards, decide how thick the layer needs to be. This table puts the layer thicknesses from the technical sources side by side.

Thin-coat plaster and a skim coat do not come with a fixed number of millimetres. They are thin layers over the whole wall, intended as a base for wallpaper, and the thickness depends on the product and on how flat the wall already is. How much a skim coat has to level out therefore also determines how thick it ends up.

Why is 10 mm the standard for gypsum plaster?

In the MP 75 technical data sheet, Knauf states that a layer thickness of 10 mm is needed to guarantee the optimum performance of the gypsum plaster.

At the same time, the same sheet acknowledges that a wall is never perfectly flat. That is why 5 mm is permitted locally, as long as most of the wall has a 10 mm layer. A bulge in the brickwork therefore gets a thinner layer, a hollow a thicker one.

If a wall has to be levelled so far that more than 25 mm is needed, the plaster goes on in two coats. The first coat is roughened, and the second only goes on once the first is completely hard. On a wall, the limit is 40 mm.

How thick do you plaster a ceiling or a plasterboard wall?

A ceiling is stricter than a wall. According to Knauf, MP 75 gypsum plaster goes onto a ceiling of masonry material in a single coat, up to a maximum of 15 mm. If more is needed, Knauf advises consulting its technical department first. A ceiling with large differences in height therefore calls for a different approach than simply putting more plaster on.

Plasterboard is a completely different story. According to the sheet, MP 75 is intended for rough, absorbent masonry substrates and plaster carriers. Plasterboard is already flat, and what matters there is the joints and the surface, not centimetres of plaster.

For plasterboard, the European gypsum industry body Eurogypsum and the plasterers’ association UEEP have defined four finish levels. At the highest level, Q4, a finishing layer of at least 1 mm goes over the whole surface, for a smooth wall you can paint straight away. Which of the finish levels for plasterboard you need depends on what is going on the wall.

Isn’t a thicker layer of plaster stronger?

No. A thicker layer is not better, it is only needed when the wall is crooked or hollow. Every extra millimetre needs more drying time and makes the wall thicker.

You notice that drying time straight away in your schedule. According to Knauf, gypsum plaster can be dry enough after about four weeks under good conditions, and that applies to a normal layer. A thin skim coat is dry in 3 to 5 days for a complete home. So find out beforehand how long plaster needs to dry when you are making a schedule.

The extra thickness also shows at window frames, door frames, skirting boards and built-in cupboards, where the new wall sits further forward. When plastering over a textured finish, that often plays a part, and it is one reason to choose carefully between removing a textured layer or plastering over it.

And in a new-build home, thickness does not help against cracks. A new house settles and shrinks over the first few years, and a hard layer of gypsum cracks along with it, thick or thin. That is why we usually choose thin-coat plaster with reno fleece there, which bridges small shrinkage cracks. This is why thin-coat plaster in a new build, with reno fleece over it, works better than a thick layer.

How do we decide how thick the layer on your wall will be?

When you make your request, tell us whether it concerns a wall, a ceiling or plasterboard, and whether there is an old layer or a textured finish on it. The free quote you receive within 24 hours will then already allow for the right finish.

We determine the layer thickness itself during the on-site visit. We look at how flat the wall is, what the substrate is and whether an old layer has to come off. That tells us whether a thin layer is enough, or whether the wall really has to be levelled.

With us you pay per m², not per millimetre. Plastering a paint-ready wall costs €22.99 per m² and a paint-ready ceiling €23.99 per m², always including materials. If a wall needs a lot of levelling, you will see that in the quote beforehand.

Prices exclude VAT. For a home more than 10 years old, VAT is usually 6%, otherwise 21%.

The work is done by one of our 32 plasterers, from the team of 97 tradespeople on permanent contracts.

If you would like your walls and ceilings finished with a different type of plaster, we work with the rates on our prices page.