painting new plaster

Painting New Plaster – A Step-by-Step Guide

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Transforming your home decor often involves painting new plaster, which has some key differences compared to painting ‘old’ plaster. 

Fortunately, producing a nice smooth finish in the colour you love is a relatively simple and cost-effective way of giving your home a stunning new look.

Before you get started though, there are three common questions that DIY enthusiasts often ask when it comes to painting new plaster:

  • How long should I wait for fresh plaster to completely dry before painting new plaster?
  • What type of paint produces the best possible finish on new plaster?
  • Should I seal bare plaster with PVA?

In this post, I’ll tackle all these questions and more.

Please note that this article only deals with painting INTERNAL walls/ceilings.


Tools & Materials

Tools

  • Canvas drop cloth to protect carpets
  • Scraper
  • Bucket
  • Stirring paddle drill attachment or stirring stick
  • Paintbrush set 
  • Roller and tray (medium to tight roller sleeve)
  • Filling knife

Materials

  • Plastic sheets
  • Rosin paper to protect hard floors
  • Masking tape
  • Emulsion paint
  • Solvent-based paint for kitchen and bathrooms
  • PVA as a sealer for solvent paints only. For emulsion paint, use mist coats (see mists coats below)
  • Filler
  • 220-grit sanding block

What’s The Best Paint To Use When Painting New Plaster?

Picking the right paint depends on the room you’re painting, the bare plaster type and your budget.

The humidity in kitchens and bathrooms cause water-based paints (emulsions) to soak up the water vapour, which can make them unstable and likely to peel or harbour mould spores. Therefore, it’s best to use solvent-based paints for kitchens and bathrooms. Some companies even make special kitchen and bathroom paints which come in a vast range of colours.

For the other rooms in your home, go with good quality emulsion paint. Good quality paint will need fewer coats, last longer and produce a much better finish when compared with cheaper paints. Use this link to find the best options for your home.


Step-By-Step Instructions

1. Wait For New Plaster To Dry

Newly plastered walls must be left to completely dry out before you start painting.

Drying time depends on several factors such as; time of year, heating, bare plaster type and the number of plastered layers.

You can expect new plaster to be completely dry after about three weeks, assuming you have central heating. If you don’t have central heating, it could take up to 6 weeks.

A newly plastered wall is much closer to the colour in Fig.1 than Fig. 2 (see images below). Once the wall is completely dry, the wall should match the colour in Fig. 2. and be uniform in its colour.

Fig. 1. Colour of a freshly plastered wall (do NOT paint!)
Fig. 2. Colour of a dry plastered wall (ready to paint)

Why Do I Need To Wait For Plaster To Completely Dry?

You shouldn’t be painting plaster before it’s completely dry because paint forms an airtight skin on top of the plaster. 

This airtight skin results in moisture being trapped underneath the paint instead of evaporating off the plaster. The trapped moisture will either move deeper and develop mould in the wall or will mix with wall salts and become Efflorescence.

In either scenario, you’ll have an expensive problem to fix. As always, prevention is better than cure!

Can I Speed Up The Drying Time?

Make sure newly plastered rooms are well ventilated by opening doors and windows. This will allow natural air ventilation to flow through the room, gently drying your plaster.

Don’t be tempted to turn the heating up full whack, as rapidly drying plaster can cause cracking.

2. Prepare The Room For Painting

All the prep work listed below should have already been done for the plastering process. However, just in case they haven’t, here are the essential steps:

  • Move as much furniture as possible out of the room. Any furniture that needs to stay must be covered with plastic sheets
  • Cover hard floors with rosin paper and cover carpet with canvas drop cloths
  • Use masking tape to cover other areas that shouldn’t be painted

For much more info on how to prepare a room for painting, please check out my guide to Painting A Room With No Mess – 27 Top Tips.

3. Remove Excess Plaster (if necessary)

Look closely at the surface and you will most likely see unwanted little blobs and drops of plaster. They are not so obvious at first, but they stand out later when you’ve finished painting. Use a scraper to remove all the big bits you find.

For smaller imperfections, use 120 to 240 grit sandpaper and smooth out any marks.

Using a flat rubbing block, lightly and carefully run the sandpaper over the plastered surface. Avoid rubbing one area too much, as you’ll end up creating dips and/or polish the surface so that paint won’t fully adhere to the plaster. 

Regularly check your progress by running your fingertips over the plaster. After you’ve smoothed out the damage, you shouldn’t feel any difference when comparing the sanded area and the area surrounding it.

4. Sealing New Plaster

New plaster is extremely porous, so if you use undiluted paint, the paint’s moisture will be sucked up by the plaster. The result is dry paint that won’t bond with the plaster.

Therefore, you must seal the plaster before applying the finish paint. For water-based paints, seal the plaster with one or two mist coats.

Mist coats are diluted coats of paint that plaster will suck up like a sponge and use to fill its pores.

For solvent-based paint (used for kitchens and bathrooms) use PVA as your sealer.

How To Create And Apply Mist Coats

IMPORTANT NOTE: Make sure that you DON’T use a vinyl emulsion for your mist coat. Vinyl emulsion forms a skin on the surface of your plaster that will be prone to peeling.

As mentioned above, solvent paints should be sealed with a PVA adhesive and NOT mist coats. PVA should also be mixed with water and by the same ratio as below.

1Mix Emulsion With Water 

  • Mix standard emulsion with water. The ratio should be four-parts emulsion to one-part water.
  • Stir thoroughly using a stirring paddle attachment for your drill. If you don’t have a stirring paddle attachment, just use a regular stirring stick.

Note: Depending on your emulsion, you may have to alter the above ratio to achieve the right mix. If you need more info, check out this mist coat guide.

2Apply Mist Coat On Walls

  • Apply the emulsion-water mix to the plastered surface. Use a brush for edges and a roller for everywhere else.
  • Check that the plaster is absorbing the liquid. You may even hear a sucking sound while the plaster is absorbing the mist coat
  • If you find that the plaster is not absorbing the mix, add more water to a max mix of 50/50
  • In most cases, one mist coat is enough. However, it doesn’t hurt to add a second one if you feel the need to.

5. Fill And Sand Any Imperfections

Once the mist coat has dried, imperfections should be filled and sanded down.

  1. Mix up some filler
  2. Using a filling knife, apply the filler to any holes and cracks you find and wait for it to dry.
  3. After the filler has dried, use a 220-grit sanding block to smooth it
  4. Touch up the filled areas with the mist coat mix 

6. Paint Wall With Finish Coats

Once the filler touch-ups have dried, your wall/ceiling is ready for its finish coats.

Apply two or three finish coats by following the same steps used for the mist coat.

For more information on painting, please check out this article, under the heading ‘Painting Technique’. You’ll find some great tips on how best to use rollers and brushes, so I highly recommend you check this out before you start painting.

Pro Tip: The humidity in kitchens and bathrooms means that emulsion paints soak up water vapour which makes them unstable and likely to peel or harbour mould spores.

Fortunately, several paint manufacturers produce special kitchen & bathroom paint that protects against these issues. Be sure to ask your local DIY store about these paints when painting kitchen and bathrooms


Painting New Plaster FAQ

Below is a list of questions I’ve had since originally writing this post that hasn’t been addressed above.

Please keep the questions coming and I’ll try to answer them in this section.

What If I Cannot Wait For My Plaster Dry?

If you really can’t wait, paints called microporous paints will allow the plaster to continue evaporating and breathing while still drying.

Typically, microporous paints are thinner than water/solvent-based paints, so once the surface is dry, I recommend you paint over them using emulsion. Remember, only add the extra emulsion coats once the fresh plaster is bone dry.

If you’re planning on using microporous paints, read the product’s instructions with regards to thinning and applying a mist coat to fresh plaster.

Although the microporous paints option is a viable solution if you’re in a bind, I still recommend waiting for the plaster to completely dry out before painting.

Do I Always Have To Prepare New Plaster Before Applying The Mist Coat?

This depends on the skills of the plasterer. If you hire a highly rated professional plasterer based on trusted referrals and reviews you should be confident in their work.

You may get lucky and avoid this step, but no matter how good and careful the plasterer, imperfections can happen. E.g. dust & debris can settle on new plaster, trowels can catch, etc.

In most cases, imperfections such as scratches and lumps can be rectified using sandpaper. See step 3 above for instructions.

Should I Apply A Second Mist Coat?

A second mist coat is normally unnecessary, but it doesn’t hurt. So for peace of mind, go ahead and apply a second coat if it makes you feel better.

Apply the second mist coat using the instructions provided in step 4 above, and remember to wait 24 hours for it to completely dry.

Once the surfaces are smoothed out, sealed and 100% dry, continue painting the finishing coats (step 6).


Final Thoughts

I hope you found this post useful and now feel empowered to paint your freshly laid plaster. To see how the pros do it, check out this video: 

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