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Summary: Preparing new plaster walls and ceilings for wallpaper
Newly plastered walls and ceilings need to be sealed. For a full explanation as to why, please see our painting new plaster project.
To seal a surface before you hang wall paper the wall also needs to be totally dry. Information regarding this is also contained in the above project.
Sealing a surface for papering can be done using a proprietary product called size. This is a gelatinous solution which is mixed with water and applied straight onto the wall and allowed to dry. It is also used in glazing paper and stiffening textiles It can be papered over while still wet but, with the addition of wallpapering paste it sometimes makes the wall too slippery to hang paper properly.
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Pasting brush £3.69 | ![]() |
Papering brush £3.69 |
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Pro Table £45.00 | ![]() |
Scissors £2.59 |
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Dust sheet £7.99 | ![]() |
Pro Scuttle £3.99 |
A dilution of the wallpaper paste you are going to use can also be used as a form of size to seal the wall. Most pastes will have a sizing solution on the packet but a rough guide is to use 25% more water in a sizing solution.

Wallpaper paste makes 12 pints £1.59
When you intend to apply a vinyl paper to the surface, it is best to prepare the walls by sizing with a dilution of a paste with fungicide in it. Vinyl papers are air proof and as a result any dampness at all that is trapped behind the paper will not be allowed to evaporate out. This could turn to mould.
Apply the size or diluted paste with a large emulsion brush.
Much more construction information is available in our bookstore. All the tools and fittings you need in the toolstore.