Walls just plastered?

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There are numerous occasions when you may need to know how to paint on fresh plaster. Perhaps you had a room replastered or built a new space with all new walls.

Painting a room is one of the simplest, cheapest, and most effective DIY projects available. You simply need to select one of the best kitchen paints, one of the best washable paints, or one of the best bathroom paints, depending on the room. It's a completely different story if you're painting new plaster. For a professional finish, you must understand the unusual properties of fresh plaster, as well as any priming that may be required. You'll also need to have a little patience.

How to Paint Fresh Plaster

The professionals at Farrow & Ball (Opens in new window) 'It is critical that new plaster and plasterboard be completely dry before painting over it.' For new work, such as new plaster, dilution of the first coat, known as the mist coat, is essential because it allows the paint to sink into the surface and bind to it. To finish, apply two full, undiluted coats. '

What will you need to paint on new plaster?

1. Check that the plaster is dry.

Plaster absorbs moisture like a sponge, so the longer you let it dry, the easier it will be to achieve an even finish. The time it takes for plaster to dry depends on the temperature of the room, ventilation, and the thickness of the plaster.

Wait four weeks for every 5mm of plaster depth, as a general rule. Before you begin painting, check for dark patches on the freshly plastered surface; a uniform, light color is a good indicator of whether your plaster has dried thoroughly.  

Newly constructed or altered rooms also take time to settle, so waiting will allow you to fill any cracks that form as a result before painting.

2. Prepare a mist coat

Fresh plaster is extremely porous, and any moisture absorbed into the wall will be quickly absorbed. This is why you must water down your first paint layer (known as a mist coat).

To make a mist coat, mix a lower-cost emulsion paint in a color similar to your top coat with water. The ratios for this will vary depending on the paint you're using, so check the label - but three parts paint to one part water should suffice.  

Stir the solution until it has an even consistency with no water on top of the paint. Fresh plaster must be able to breathe beneath the paint in order for any moisture to escape, so use a non-vinyl water-based paint.

Top tip: If you have a large number of rooms to paint, a large batch of white trade emulsion will last you through several mist coats.

3. Mist coat

Applying the first coat of mist paint can be a messy job because the paint is thin and runny, so make sure you have dust sheets down and any furniture covered. Masking tape should be used to protect the skirting/baseboards and any trim, as well as to cover light switches or sockets and windows.

Pour the mist coat into a paint tray and apply an even amount with a foam roller. Roll it over the plaster in smooth, upward motions until the entire surface is covered. To get into any corners or areas that the roller cannot reach, use a smaller paint brush.  

Top tip: When misting fresh plaster, keep an eye out for drips and roll over them before they dry.

4. Let the mist coat dry.

A mist coat will dry in about 24 hours, depending on the conditions in the room. Once dry, begin applying top coats.  

5. Apply the final coats

If you are right-handed, begin at the top left corner of a wall and work your way to the right. If you are left-handed, you should work in the opposite direction. This will keep paint from getting on your favorite decorating dungarees.  

Paint the corners of the wall with a brush and the rest of the wall with a roller. Allow the first coat to dry completely (overnight if necessary) before applying a second coat.  

Can I paint directly on new plaster?

Once the freshly plastered wall is completely dry, the mist coat paint step is critical because it acts as a primer. According to Dulux, the correct ratio is 'three parts paint to one part water should work,' and if you want a (slightly) less messy job, you can use Dulux Sealer for Plaster. (Opens in new window) Remember to fill any holes in the plaster before beginning this project for a smoother finish.

What if the mist coat is too thick?

You'll know if your mist coat is too thick because it won't absorb well onto the new plaster. This can be the case with some store-bought plaster sealers, so if you buy one rather than mixing emulsion paint and water yourself, test it on a small patch first. It should be fine to proceed if it is a little thinner than single cream consistency and does not sit on the surface. If it does sit on the surface and appears a little thick, you'll probably have to water it down another 50/50.