You’ve probably heard that breathable paint is a good choice for your home. It reduces the risk of moisture-related damage, can improve indoor air quality and supports a more comfortable living environment. It’s particularly useful in older or period properties where materials like lime plaster have been used and need a finish that lets them breathe.
But what happens if your walls already have several layers of conventional, non-breathable paint on them? Do you really need to strip everything back before you can use breathable paint?
The short answer is: not necessarily.
While painting a breathable paint over a non-breathable coating won’t magically make the layers underneath breathable, there are situations where a breathable paint such as Claypaint can still be a good choice. That’s because Claypaint is not only highly vapour permeable, it’s also hygroscopic, helping to regulate moisture and humidity within a well-ventilated room.
So, before you reach for the paint scraper, let’s look at what breathable paint actually does, when you might need to remove old paint, and when you can simply work with what you already have.
Breathable v non-breathable paint
You don’t actually hear breathable walls exhale. But they do release water vapour rather than holding onto it.
This is particularly useful in traditional homes with solid walls, lime plaster or lime render. These breathable building materials absorb and release moisture. A breathable paint helps them keep doing that job. Breathable paints also tend to contain low VOCs, which contribute to better indoor air quality.
Non-breathable paints, on the other hand, trap moisture in your walls. If moisture is present within a wall, a coating that restricts vapour movement can make it harder for that moisture to escape. In turn, that can cause dampness, condensation, mould growth and even structural issues. Many modern paints, like standard emulsion paints, vinyl, acrylic and oil-based paints fall into this category.
Breathability isn’t simply a case of a paint being either “breathable” or “non-breathable”. It’s more of a sliding scale. You can see how breathable paint is by looking at its Sd value. Generally, a breathable paint has an Sd value of 1 or below (ideally less than 0.5). The lower the Sd value, the easier water vapour passes through.
You can also check the Moisture Vapour Transmission Rate (MVTR). This indicates how much moisture can move through a surface in 24 hours. You want a higher MVTR rating to indicate better breathability and moisture vapour transmission.
How do you identify non-breathable paint or plaster on a wall?
Generally, it’s not immediately obvious whether you have a non-breathable or breathable interior paint on your walls. You may inherit decades of painted layers to tackle on your interior walls. Unfortunately, most decorators don’t leave a label on their painted wall. You can hunt for clues like old paint cans or renovation notes, but often it’s a case of detective work.
What you can do is look out for signs of damp walls as they indicate a lack of breathability. This can include peeling, flaking or bubbling paint. However, damp patches don’t automatically mean you have non-breathable paint, they can also be caused by poor ventilation and condensation, which is particularly likely in bathrooms and kitchens that can get rather steamy.
How do you strip non-breathable paint from an interior wall?
If you’re looking to get the most from a breathable paint system, removing a non-breathable coating is best practice, particularly on traditional, breathable substrates such as lime plaster.
However, there’s no need to strip paint simply for the sake of it if the existing coating is sound and well adhered. Removing firmly attached paint can create more work than necessary and, on older walls, aggressive preparation can sometimes damage the surface underneath.
If you do decide to remove the old coating, preparation is key. Take your time and aim for a sound, stable surface on your internal walls before applying your new breathable paint.
1. Scrape away loose and bubbled paint: Gently lift flaking paint with a scraper or putty knife. Make sure you remove every bit of old paint. Stop if the plaster starts coming away with it though. The aim is to remove the coating, not excavate the wall. Avoid harsh, chemical paint strippers too. Look for kinder, eco-friendly alternatives.
2. Sand and smooth: Give rough edges a light sanding to help them blend into the surrounding surface. Wipe away any dust afterwards.
3. Fill any dents or hollows: Scraping may reveal a few cracks, dents or hollows. Fill these with a filler suited to your wall. Keep it level with the surrounding surface. Once it’s fully cured, sand lightly again for a smooth, even finish.
4. Clean the wall thoroughly: New paint needs a clean surface to stick to. Remove dust, dirt, grease and any cleaning residue. Once the wall’s clean and dry, treat any remaining oil or grease stains with our Isolating Primer, following the instructions and allowing it to dry before painting.
5. Prepare the wall for painting: If the surface feels powdery, our breathable Wall Glaze or Bonding Primer may be able to stabilise it. Fresh plaster needs time to dry and cure before decorating, so ask your plasterer for guidance. Follow your paint’s instructions for applying a diluted first coat to bare, absorbent plaster.
6. Repaint carefully: Now, it’s time for that fresh coat. Choose a highly breathable paint, such as Claypaint, to allow water vapour to pass through and keep your wall dry.
Why would you paint breathable paint over non-breathable paint?
Here’s where things get a little more interesting.
If you paint a breathable paint over an existing non-breathable coating, the old coating underneath doesn’t suddenly become breathable. The original layer is still there, and it can still restrict the movement of moisture through the wall.
If you’re renovating a traditional property with lime plaster or another breathable substrate, removing a sound non-breathable coating can therefore be worthwhile where practical. It gives the wall the best opportunity to benefit from a fully breathable paint system.
But stripping every last layer of paint isn’t always necessary. If the existing paint is firmly attached, the wall is in good condition and you don't want to undertake extensive preparation, Claypaint can still be a good option.
Claypaint is more than just vapour permeable. Its high clay content also gives it hygroscopic properties. This is true of our Claypaint specifically, not all breathable paints.
Its hygroscopic nature means it can absorb moisture from the surrounding air when humidity and condensation levels rise and release some of that moisture again when the air becomes drier. In other words, it can help to buffer fluctuations in humidity within a room.
This can be particularly useful in a well-ventilated home, where normal day-to-day activities such as cooking, bathing and drying clothes create changes in humidity.
So, if you have an existing non-breathable paint coating that you’d rather not strip, perhaps because it’s sound and well adhered, or because you’re trying to avoid a messy decorating job, applying Claypaint can still bring the benefits of its hygroscopic, moisture-regulating properties to the room.
How do you strip non-breathable paint from lime or masonry?
Heritage and listed buildings with traditional substrates need a little extra care. Lime plaster, lime render, distemper, old brick and stone need a gentle approach. Removing old paint too aggressively can damage and remove the surface beneath it, so if you’re working with historic masonry or fragile lime finishes, it’s worth speaking to a specialist before reaching for the paint stripper.
Our Claypaint’s a highly breathable wall paint for interior lime plaster, with a beautifully soft, ultra flat matt finish. For exterior walls, look for a breathable masonry paint (such as a silicate paint). Our Silicate Masonry Paint is a vapour permeable alternative to conventional masonry paint and limewash. It provides a durable, long-lasting, classic matt finish on lime, concrete, brick, stone and pebbledash.
Looking for breathable paints?
If you’re decorating an older or period property, choosing the right paint can make a real difference to how your walls perform.
Look for the paint’s technical credentials rather than relying on the word “breathable” alone. You can find information about Sd values, moisture vapour transmission and other paint attributes in the technical data sheets on our website.
For interior walls, Claypaint is our most breathable paint. Its high clay content gives it a beautifully soft, ultra-flat finish as well as hygroscopic properties that help regulate moisture and humidity.
For exterior walls, Silicate Masonry Paint offers a highly vapour-permeable, durable finish for suitable mineral and traditional masonry surfaces.
