How to paint on new plaster for a pro finish

Achieve a professional finish when painting on new plaster walls with the perfect mist coat ratio and technique.

Couple painting a wall with blue
(Image credit: Getty | Image_Source_)

There are many occasions where you might need to know how to paint on new plaster. Perhaps you have had a room re-plastered, or built a new space with completely fresh walls.

Painting a room is one of the easiest, cheapest – and not to mention most effective –DIYs out there. But, if you're painting new plaster, it's a whole different ball game. You need to understand the unusual properties of fresh plaster, any priming involved and more for a professional finish. You'll need to factor in just a little patience also...

The experts at Farrow & Ball say 'It’s really important that new plaster and plasterboard is fully dry before you paint over it. For new work, like new plaster, dilution of the first coat known as the mist coat is essential, as this allows the paint to sink into the surface and bind to it. Follow with two full, undiluted coats to finish.'

What will you need to paint on new plaster?

How to paint on new plaster

Start by opening doors and windows, and don't start painting until the plaster is bone dry. This could mean waiting a few days or even weeks for a room to dry. It is worth the wait though to do it right. Follow these steps for perfect results every time.

1. Make sure the plaster is dry 

Plaster will suck up any moisture like a sponge, so the longer you leave it to dry, the easier it will be to achieve an even result. The time it takes for plaster to dry out will depend on the room's temperature, ventilation and the plaster's thickness.

As a general rule, wait four weeks per 5mm of plaster depth. Ensure that there are no dark patches on the freshly-plastered surface before you being to paint – a uniform, light, color is a good indicator as to whether your plaster has dried thoroughly. 

Newly built or altered rooms also take a while to settle, so waiting will mean you can fill any cracks that form as a result, before you paint.

2. Make a mist coat 

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

To make a mist coat, combine a cheaper emulsion paint in a similar color to your top coat with water. The ratios for this will vary according to the paint you are using, so check what it says on your paint tin – but around three parts paint to one part water should suffice. 

Stir the solution until you have an even consistency with no water sitting on top of the paint. Fresh plaster needs to be able to breath underneath the paint to allow any moisture to escape, so make sure to use a non-vinyl water-based paint.

Top tip: If you have lots of rooms to paint, a big batch of white trade emulsion will see you through several rooms worth of mist coat.

3. Prime with a mist coat

Applying the first coat of mist paint can be a messy job as the paint will be thin and runny, so make sure you have put down dust sheets and covered any furniture. Fix masking tape along the skirting/baseboards and any trim to protect them, and cover light switches or sockets and windows.

Pour the mist coat into a paint tray then roll an even amount on to a foam roller. Roll it over the plaster in smooth, upward motions until you have covered the whole surface. Use a smaller paint brush to get into any corners or areas that cannot be reached with the roller. 

Top tip: When applying your mist layer to fresh plaster, keep an eye out for any drips, rolling over them before they dry.

4. Allow the mist coat to dry 

A mist coat will take around 24 hours to dry, but this will depend on the conditions in the room. Once dry, you can start applying top coats. 

5. Apply the top coats

If you are right handed, start in the top left hand corner of a wall and work to the right. If you are left handed, work in the opposite direction. This will stop you getting any paint on your beloved decorating dungarees. 

Cut in paint around the corners of the wall using a brush and fill the rest of the wall using a roller. And allow the first coat to dry thoroughly (overnight if you are unsure) before adding a second coat. 

Can I paint straight onto new plaster?

The mist coat paint step once the freshly plastered wall is completely dry, is essential as this acts as a primer. The correct ratio according to Dulux is 'Three parts paint to one part water should work' and if you want a (slightly) less messy job, you can cheat with Dulux Sealer for Plaster. Remember also to fill any holes in plaster ahead of starting this project for an even smoother finish.

What happens if the mist coat is too thick?

You'll be able to tell if your mist coat is mixed too thickly as it won't absorb very well onto the new plaster. This can be the case with some shop bought plaster sealers so if you are buying one rather than mixing emulsion paint and water yourself, first try what you've bought on a small patch. If it comes out a little thinner than single cream consistency and doesn't sit on the surface it should be fine to go ahead. If it does sit on the surface and seems a little too thick, it's likely you'll have to water it down a further 50/50.

Hebe Hatton
Hebe Hatton

Hebe joined the Real Homes team in early 2018 as Staff Writer. As a renter, she is always looking for creative ways to make her flat feel like home. She loves boho and 70's style and is a big fan of Instagram as a source of interiors inspiration.

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