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There are many things to think about when plastering. From mixing the plaster correctly to applying it the right way. If you get all this right, your plastering job should have the perfect finish.
However, once the job is done, you must also consider how it dries, the speed it dries and where that moisture all goes. For example, can you expect plastering to cause condensation?
Plastering can cause condensation. When plastering, you will use a lot of water and as it dries, this moisture will evaporate and leave the plaster mix, allowing the plaster to harden.
However, that moisture needs to go somewhere, and the air can only hold so much water vapour. As the air reaches high relative humidity, this will result in condensation settling in cooler areas such as windows.
Why you will probably notice condensation after plastering
Once you have applied plaster and left it to dry, you may return to find lots of condensation on windows and other cold surfaces.
At first, this might seem unusual. However, it is common when plastering. The process of mixing plaster involves using lots of water. The mix will usually contain around a 50/50 mix of plaster and water. This means there is a large volume of water contained within the plaster.
As the plaster is applied to the wall wet, it then must go through the process of drying out. It’s important to allow the plaster to dry naturally, but the water within the plaster will escape into the surrounding air.
The air will only be able to hold so much moisture, which means the excess will then settle on cold parts of the room as condensation. Condensation occurs when the air is saturated with water. It is then unable to hold the water, so when it reaches a cold surface, it reaches its dew point and then condenses.
Best way to reduce condensation
The reality is that you should expect some form of condensation when plaster is drying. As mentioned, there is a lot of water in plaster, which must go somewhere when it is drying out.
If the room is unventilated, all the moisture will sit in the air until it cannot hold any more. The result is damp windows and cold areas, but there are ways to reduce the amount of condensation after plastering.
The main thing you can do to reduce condensation, is make sure that the room is well ventilated. You need to make sure that air is flowing around the room. To do this, you can simply open a window or a door. This will allow the air to move and escape the room, helping to reduce condensation.
How to dry out newly plastered walls
After you have finished plastering, it is crucial that your plaster dries correctly. If this process is not completed in the right way, then it could damage your plaster.
The main way to dry out newly plastered walls is to allow it to dry naturally. Ideally, you should avoid forcing the plaster to dry. So, if you have the time, then you should ensure you have the right ventilation, while giving the plaster time to dry. The process of drying plaster involves several chemicals in the mix and a reaction between them.
When you remove the water too quickly, you will stop the chemical ration too soon. This will mean your plaster will not harden, and you will begin to see cracks.
It is possible to use a dehumidifier, but it is not necessarily recommended. A dehumidifier will remove moisture from the air. This will help to speed up the drying process. However, you would need to make sure you manage this correctly and put the dehumidifier on a low setting, to avoid drying too quickly.
If the plaster dries out too quickly by using a dehumidifier, it will result in the plaster becoming too dry, too fast. This can then result in cracking, which will leave your plaster requiring further work.
You could use a heater which might be the better option, although you would still need to take care. If you heat the room too much, it causes the plaster to dry too quickly, which could also lead to cracking. If you don’t have a heater, you can always put your heating on low while maintaining good ventilation.
How long will plaster take to dry before you can decorate?
There is no specific drying time for plaster because it relies on several things such as the temperature and ventilation. If you are keen to decorate you will need to make sure that you wait until the plaster is completely dry.
The amount of time you need to wait, will depend on several factors, including:
- The amount of plaster you applied
- The humidity
- The time of year and natural temperature
- Whether there is plasterboard backing
If you have applied plaster onto plasterboard and have covered an entire wall, then this will dry relatively quickly. Therefore, you can begin to decorate after around 3 to 4 days.
If you have applied several layers of plaster, such as backing plaster and then skimming over, then this will take longer to dry. Therefore, you can expect to decorate, after around 5 to 7 days.
Of course, the factors mentioned above will affect the drying time. Furthermore, if you plaster in the winter, then you should expect the drying time to increase.
Before you begin to decorate, you should make sure that there are no dark patches. The colour should be light and consistent, as this is a sign that the plaster has dried thoroughly.
Plastering can cause condensation and that can result in other issues such as mould. Despite this, you can reduce the amount of condensation by ensuring you have the right ventilation in place.
While it is possible to use dehumidifiers and heaters, you should do so with caution. By speeding up the drying process, you could cause further problems which will then need rectifying.