Lime plasters can create beautiful finishes. Some people like the finish so much that they don’t apply decorative paint! However, most people will want to apply some paint to their new lime plaster. So how soon can you paint over fresh lime plaster?
Generally, you should wait until the plaster has fully set. This is a lengthy process, especially if you use non-hydraulic lime. You can expect to wait around four weeks, which will largely depend on the environmental conditions. If you plan on using limewash, you can apply it while the plaster is still ‘green’. But for all other paints, the lime plaster must be fully cured before painting.
Now we’ve had a brief insight into how long you should leave lime plaster before painting, let’s take a more detailed look.
What is Lime Plaster?
Lime plaster is made by mixing either hydraulic or non-hydraulic lime (fat lime or lime putty) with various sands, aggregates and water. It’s often used in traditional construction as an alternative to modern cement-based plasters and renders. It is prized for its breathability, flexibility, and ability to protect the building, wall or ceiling it has been applied to.
In some cases, fibres are added to lime plasters to help increase tensile strength. Traditionally in the UK, horse and goat hair are mainly used. Horse hair is mainly used with base coat plasters and is especially helpful when using lime plaster on laths due to the added strength.
Goat hair is finer hair. This has resulted in it being used mainly in finish plasters. Some people like having the added texture that the hair will provide. Although it’s more common to use horse hair where strength is needed, such as when doing work involving laths, and then finish with the surface with an unhaired fine lime skim plaster.
Related article: Lime Vs Cement Plaster: The Differences Explained
When Can You Paint Over Fresh Lime Plaster?
For most paints, lime plaster must be fully cured and dry before application. This is because residual moisture within the plaster, when it hasn’t fully cured, can cause some paints to peel, bubble or otherwise fail. Limewash is the only paint that can be applied before the plaster has fully cured.
Limewash can be applied before the plaster has fully cured and is still ‘green’, meaning the surface is hard, but it may still be slightly damp or not yet fully cured. This is because limewash, like lime plaster, is a vapour-permeable material. This will allow both the paint and the plaster to cure.
Additionally, limewashing a lime plaster surface before it is fully cured can cause the plaster to dye mildly. This can create a very beautiful and often deeper colour.
What Paints can be Used on Lime Plaster?
Lime plaster is a vapour-permeable material. This means it can absorb moisture deep within the wall and slowly bring it to the surface, where it can evaporate without causing any damage. This process mustn’t be blocked or sealed.
This is why vapour-permeable or breathable paints are a must for lime plaster. Any paint that is waterproof, water-resistant or will seal the surface is unsuitable for lime plaster. So what are the best paints for use with lime plaster?
The best paints for lime plaster are usually lime based. This includes lime paint and limewash (which are different types of paint). Other natural, breathable paints, such as clay paint, mineral paint and distemper, can be used.
Related article: What Are The Best Paints For Lime Plaster?
Why Paint Lime Plaster?
When painting lime plaster, it’s important first to note you don’t have to. Lime plasters by themselves create a beautiful finish. You can even get lime plasters specifically made with desired colours and textures.
However, sometimes it’s nice to have a change. Plastering your walls with a white or neutral-coloured lime plaster will allow you to choose your preferred colour. Additionally, limewash and lime paint help naturally protect, sterilize, and kill mould.
Painting over lime plaster is a great way to give your walls a fresh, updated look. It can also have practical benefits, such as providing extra protection against moisture and helping preserve the plaster’s finish.
Additionally, painting over lime plaster allows you to customize the colour of your walls to match the rest of your home’s décor. Painting over lime plaster helps create an inviting atmosphere while protecting it from water damage and other environmental factors.
Related article: Why Should You Consider Using Lime Plaster or Render?
How to Tell When Your Plaster Has Fully Cured?
In good, warm and dry conditions, lime plaster will set at a rate of around one day per mm of thickness. Most 3-coat lime work, which is the thickest, will be around 30-40mm thick. In poor conditions, lime plaster can take much longer to set. This is why there’s no standard set time, as it depends greatly on the conditions.
As a general rule of thumb, you should wait at least 28 days before painting over fresh lime plaster. This will help ensure that the plaster has had enough time to cure and will provide a strong base for your paint job. If the plaster still has damp patches or feels damp, it is not ready for painting.
What Happens if you Paint Lime Plaster too Soon?
Painting lime plaster too soon can have disastrous results! If the plaster hasn’t had enough time to dry and cure, the paint won’t be able to adhere to the wall properly. This could lead to bubbling or peeling of the paint and unsightly cracks in your walls.
Additionally, if the lime plaster is still damp when you paint it, the moisture in the plaster can cause mould and mildew to grow on your walls – leaving you with an even bigger mess than before. To avoid these problems altogether, make sure that you wait until the new lime plaster has fully cured before painting over it.
How do you Prepare Lime Plaster for Painting?
Preparing lime plaster for painting is an important step in giving your walls a fresh, new look. Before you begin painting, it’s essential to ensure the plaster is properly prepared. To do this, you’ll need to remove any loose or flaking plaster bits and old paint.
Once that’s done, use a damp cloth to clean off any dust or debris and then let the wall dry completely before applying any paint. Depending on what paints you use, it may be necessary to keep the wall damp while you are applying the paint. This is especially important for lime-based paints, such as limewash and lime paint.
Additionally, any paint or primer that has been applied to the lime that is waterproof must be removed. It’s extremely important that lime plaster is not sealed and can breathe. Following these steps will help ensure that your painted lime plaster looks beautiful and lasts for years!
In Conclusion
Painting lime plaster takes patience and careful timing, but it will be well worth the wait! It’s important to wait for your lime plaster to cure completely before painting – if you try to paint over the plaster too soon, you risk trapping moisture inside, which can lead to bubbling or blistering of the paint.
Not only does this ruin the look of your wall, but it also makes it more prone to damage. Furthermore, trapped moisture can cause mildew or mould growth, which is hazardous for your wall and your health! So remember: when it comes to lime plaster, wait until it is fully cured before applying any paint.
