If you’re asking yourself what’s the difference between wallpapering over new plaster and old, rest assured the process isn't entirely the same. It might not be a huge difference, but there is one key step in the process that cannot be overlooked when wallpapering new plaster. Miss it, and you’ll be heading for a decorating disaster.
It’s not just about knowing how to wallpaper a wall or ceiling – although this does help. Instead, it's about preparing the new plaster before any wallpaper is applied. This is essential for smooth, hassle-free wallpaper hanging.
Here we reveal what you need to know to ensure your newly plastered walls are perfectly positioned for your choice of wallpaper covering.
Follow these steps when wallpapering over new plaster
1. Prep the plaster and surrounding areas
As we mentioned, before you start, the new plaster needs to be completely dry. Nischal Pomu, Director at Platinum Paints, shares his recommendation. "Allow new plaster to dry fully for at least five days, depending on temperature, ventilation, and humidity levels.”
When the plaster is dry, it also needs to be smooth before sealing and papering. “Once dry, lightly sand the surface with a fine abrasive to remove any minor imperfections," says Nicshal, "then wipe away the dust with a slightly damp cloth.”
But, before doing any work, lay down dust sheets, cover skirting boards with painters tape to protect them and cover any furniture. To finish, use a builder's vacuum, or your domestic one, to reduce dust as much as possible before you get started.
2. Mix up your sizing solution
It's this second step that is probably the most critical step when wallpapering over new plaster. 'Sizing' is the process of sealing new plaster. New plaster soaks up liquid, making it very difficult to put up wallpaper without treating the plaster first. Therefore, without sizing/sealing, the wallpaper will almost instantly stick and stay in place, making it very difficult to move.
The best method is to apply the size directly to the wall, and there are a few options that you can use:
- Dilute wallpaper paste by adding a couple of extra litres of water to the recommended mix. For example, a typical mix for normal wallpaper and lining paper is 7 litres per sachet
- Use a specific wall sealer such as this Solvite Wall Sealer from Amazon
- Apply a mist coat, a method used when painting new plaster
Nischal Pomu also offers another option.
“I recommend applying a coat of Zinsser Gardz (available from Amazon), which penetrates into the surface, binds any residual dust, and creates a solid, stable base for wallpaper adhesion," he says.
All of these methods will help seal the plaster, readying it for wallpapering. However, do note that the diluted sizing mix you have used to seal the walls won't be any good for actually hanging wallpaper. Read our guide on how to dispose of wallpaper paste when you have finished with it as you'll need a new mix once you're ready to wallpaper.
3. Apply the size and leave to dry
With your size mixed, start in a top corner of the room using a 4-inch brush. Do one wall at a time, going around all the edges and corners to create a border. Once the edges are completed, get a paint tray, fill it with your size mix and use a 9-inch roller to apply it to the rest of the walls.
Use an extension pole, such as this Harris Seriously Good Aluminium Extension Pole from Amazon, to make it easier to reach higher areas, such as the top of the wall and ceiling.
When finished, Matt Clare, Owner, Gower Plastering Services recommends you, "allow sizing to dry completely before hanging, which typically takes two to four hours depending on the product and conditions."
If however you opt for Nischal Pomu's suggestion, "allow the Gardz to dry fully, ideally for 24 hours, before hanging wallpaper," he says. "Taking these key preparation steps will help achieve a smoother finish and a longer-lasting result."
Shop these tools to help wallpaper over new plaster
This budget-friendly 9-inch roller set is ideal for applying wallpaper paste and paint to walls and ceilings. It includes a 9-inch roller frame, two sleeves and a tray
This robust plastic paint scuttle is made from 100% recycled plastic and holds up to 10 litres of paint or paste. Suitable for 9-in rollers and features a curved bottom to reduce waste
An extra-strong wallpaper paste that can be watered down for sealing new plaster and used for hanging wallpaper. When mixed for wallpaper, it can hang up to 10 rolls
Nischal Pomu is the Director of Platinum Paints, bringing years of hands-on experience and a passion for quality decorating and painting across London.
Matt Clare is a plastering contractor with over 15 years of experience in all aspects of internal and external plastering across South Wales
FAQs
How long before I can wallpaper over new plaster?
New plaster needs to dry completely before you can think about wallpapering, but plaster isn’t a quick-drying material. “As a general rule, new plaster should be allowed to dry for a minimum of four weeks before wallpapering," recommends Matt Clare.
"In ideal conditions, with good ventilation and warmth, plaster can be ready in closer to three weeks, but rushing this is one of the most common and costly mistakes homeowners make,” he warns.
If the plaster is not completely dry, problems will occur. “Damp plaster behind wallpaper will cause mould, blistering and failure of the paper over time,” explains Matt.
How do you know when plaster is dry?
There are a few indicators, but the most obvious sign is colour. “Fresh plaster is a dark pink or terracotta tone and dries to a uniform pale, almost off-white colour throughout," explains Matt Clare. “If any darker patches remain, the plaster is still holding moisture in those areas and is not ready,” he adds.
Besides colour, touch or a tool are other options says Matt. “You can also press your hand firmly against the wall, and it should feel cool but not cold or damp.” For a more scientific solution, "a moisture meter is the most reliable way to confirm readiness, and readings should be below 12% before sizing and papering begins," he continues.
"Do not rely on the surface feeling dry to the touch alone," warns Matt, "as plaster can dry from the outside in, masking moisture deeper in the coat."
Once your walls are dry and fully sealed, you can then think about what you use to cover them. Check out our hallway wallpaper ideas, kitchen wallpaper ideas and bedroom wallpaper ideas to complete your newly decorated rooms.
