New plaster gives a nice smooth finish to walls and ceiling, making it the ideal surface for painting. Ironically, the hardest part of this job isn’t the process itself but rather the wait time. How long should you wait, when should you do it and so forth? Let’s find out the answers to these questions right here, in this post!
So, if you:
Are remodelling an older home;
Are given conflicting advice about how long you should wait for the plaster to dry;
Wonder about whether the size of the plastered area makes a difference for the time it will take to dry;
Then, read along and learn how long to leave new plaster before painting.
How long to wait before painting new plaster
Plaster needs to be fully dry before you can apply even a drop of paint on it. In the best of conditions, that being the summer months, it can take anything from a few days to a couple of weeks for the plaster to dry fully. In other, less warm seasons, that period can extend from 4 to 6 weeks. As you can see, plaster is not a quick-drying material. And how much you should wait will depend on many different factors l, such as:
The temperature within the room and building – ideal temperature is about 15 -16°C (60 – 70 °F). You should never apply plaster in freezing temperatures or during drastic temperature fluctuations.
The humidity inside the plastered room – around 60% and 80% is perfect to keep the plaster intact and allow for gradual drying.
What time of the year it is – summertime is the best time, whilst winter is the absolute worst. If you do have to plaster in the winter, know that the drying time will be 50% longer than during the summer.
Ventilation – leave the window open to speed up the process. Mind you, drafts from unglazed windows, vents or heaters may result in dry-out spots on the areas where the wind or warm airflow directly hits the wall. If the room doesn’t have proper ventilation, you will have to remove the moisture via mechanical means, such as a dehumidifier or a heating device.
Size of the plastered surface – patch repairs, where you have only one thin layer of plaster, will take around 5-6 days, whereas an entire wall will take at least 10 to 15 days before you can even apply a mist coat of paint or primer.
The thickness of the plaster – the thicker the plaster the longer it will dry.
Number of plaster layers – Walls with two or three layers of plaster (called backing plaster) will require 15 to 20 days, maybe more, to dry out completely.
One sure way to know if your plaster is completely dry is to look at its colour. Lighter colour patches mean those areas are dry, whilst darker colour ones mean it’s still wet. Don’t touch the plaster to check if it’s dry or not, you can damage or stain the surface.
What happens if I paint plaster too early
When the plaster is fresh, it is porous and absorbs moisture. If you paint over it, you will essentially trap the moisture. As a result, it will seep into the surface, rather than evaporate into the atmosphere. This in turn may generate mould growth, as damp conditions are the perfect environment for fungal spores to develop and spread. Dampness is every homeowner’s worst nightmare. Not only will the paint peel off very quickly, but you will also have a situation that’s bad for your family’s health.
Unfortunately, there’s no way to get around this problem and it cannot be reversed. If you see areas on your wall which have started to peel off, then you have painted the walls earlier than you should have. What you should do next is remove the paint with a scraping tool and do the job all over again.
A few words on dehumidifiers and radiators
Although tempting, you should never try to speed up the process of drying plaster with dehumidifiers. You see, drying is a process, where chemical reaction between the material (the plaster, in this case) and the water occurs. If the water is extracted too soon through the process of evaporation, the reaction will stop prematurely and the plaster won’t harden as well as it should. As a result, you may well see hairline cracks in your plaster walls. A dehumidifier should only be used, when there is no natural source of ventilation.
Radiators are not a better option, either, unless the room is very cold or damp. Even then, the plaster behind the radiator may dry out faster than the rest.
How to prepare plaster for painting
Once the plaster is fully dry, you should make some additional preparations before you start painting over it. You see, you need to prime the wall or ceiling first, by applying a so-called mist coat before painting the surface. Otherwise, your paint will dry out too quickly and you may end up with irregular brush strokes on your wall and an uneven finish. This is how to apply a primer.
Lay dust sheets – lay the dust sheets and tape them down. You can do this, while waiting for the plaster to dry.
Mix the primer – a mist coat is basically watered-down paint, applied in a thin layer. Its purpose is to soak into the new plaster and seal it so that the paint bonds better with the surface. You can then apply as many coats of paint as you decide. Mix 3 parts emulsion and one part water in a bucket. Check the manufacturer’s instructions as sometimes ratios may vary. The emulsion colour should be similar to the colour you plan to use later on.
Apply your mist coat – you can either use a roller or a paint brush. Work in upward motions until you cover the entire wall surface. Don’t leave drips of streaks, paint over them as soon as they appear.
Wait for the mist coat to dry – it will take about 24 hours.
Apply the paint – there is no need to sand down the wall, just apply the top coat in V motion for even coverage. You may have to apply several coats.
If you feel like this task is becoming too tedious, why not call professionals? Fantastic Services works with experienced and fully equipped professionals who can provide you with painting and decorating services. The painters use medical-grade and lab-tested antibacterial paint which protects surfaces against moss, algae and mould. This paint is also more durable and will last longer.
Besides high-quality materials and workmanship, our painting service also includes a free video survey. On it, you need to show the technician the room you want painted and explain your needs. In a few days you will get a quote. After the service is carried out, we will perform a general clean up. Get in touch today!
Plaster dries fastest during the summertime.
Always keep windows open when working with plaster and paint.
When the plaster becomes light in colour, then we can safely say that it’s completely dry.
If you see paint peeling off in certain areas on the wall, then you have applied the paint too early
Did you paint your wall yet? How did it go? Let us know by commenting!