Standard masonry paints are usually acrylic based, which means they are not genuinely breathable. The paint creates a plastic film which can trap moisture inside walls causing damp and peeling paint.
This is particularly true on heritage properties with a solid wall construction, which function best with a paint which is breathable. Using an appropriately breathable paint means the paint has properties which allow moisture to escape from the fabric of the building whilst also retaining water resistance.
There are breathable masonry paints available, but understanding the difference is important. Using the wrong type of paint can trap moisture inside walls, leading to damp patches, flaking finishes, and long term damage.
What Does Breathable Masonry Paint Mean?
Breathable masonry paint, also known as vapour permeable paint, allows moisture vapour to pass through the coating rather than becoming trapped behind it. But if you need a breathable paint to help regulate moisture in your home, how can you tell if it’s going to perform in the way you need?
Breathability is usually measured using an Sd value, which indicates how resistant a material is to water vapour movement.
As a general guide:
- Sd under 0.1 m is highly breathable.
- Sd between 0.1 and 0.5 m is suitable for many traditional walls.
- Sd above 0.5 m may begin to restrict moisture movement.
If you are aiming for a truly breathable system, it is best to choose paints with an Sd value under 0.1 m wherever possible.
Paint types that commonly achieve this level of breathability include limewash, lime paint, and mineral or silicate paints. These systems do not form a plastic film and instead allow walls to absorb and release moisture naturally, helping to prevent damp and maintain the long term condition of the substrate.
How to Tell if A Masonry Paint is Truly Breathable
The most reliable way to check is by reading the Technical Data Sheet rather than relying on product descriptions. Many masonry paints advertise themselves as breathable, but don’t have sufficient vapour permeability to allow moisture to escape effectively.
Look for:
- An Sd value or vapour permeability rating.
- Clear evidence that the paint allows vapour movement.
- Information about the binder type.
As a guide, paints made with acrylic, vinyl, or styrene binders are usually less breathable and unlikely to be suitable for heritage homes with solid walls.
More suitable breathable paint systems tend to use:-
- Lime.
- Potassium silicate.
- Other mineral based binders.
If no vapour permeability data is provided, it is often safest to assume the paint is not intended for breathable applications.
Why is Breathability Important for External Walls?
All external walls are exposed to moisture. This comes from wind driven rain on the outside, but also from humidity generated within the building. In older properties, especially those built with solid walls, moisture is managed by the wall absorbing and releasing it naturally.
If a non breathable coating is applied, this process is interrupted. Moisture builds up behind the paint layer and has no easy way to escape. This is one reason why many older homes suffer from damp and water damage. When they were originally constructed, traditional breathable paint was used which helped moisture escape. Trapped moisture has been exacerbated by modern doors, windows, and insulation which reduce air movement as well as keeping the building warm.
What Types Of Exterior Paint Are Breathable?
Truly breathable exterior paints are typically made using mineral or naturally derived binders rather than petrochemical based plastics. These paints allow moisture vapour to pass through the surface while still protecting the wall from weather exposure.
The main types of breathable masonry paint to consider are:
Lime Based Paints
Lime paints and limewash are among the most breathable finishes available, often achieving very low Sd values. They have been used for centuries on traditional buildings and are particularly well suited to lime render, stone, and other porous substrates.
They are ideal for older properties where maximum breathability is required. However, they are generally less durable than modern systems and may require more frequent maintenance.
Mineral & Silicate Paints
Mineral and Silicate paints offer a more durable modern alternative while still maintaining high levels of breathability.
These paints chemically bond to the substrate rather than forming a surface film, allowing moisture to move freely through the coating. At the same time, they provide strong weather resistance and long term performance.
This makes them a reliable choice for masonry, render, and heritage buildings where both durability and breathability are important.
Modern systems such as Graphenstone paints combine mineral technology with graphene enhanced performance, helping to improve strength, flexibility, and longevity while retaining vapour permeability. Products such as Graphenstone GCS Exterior are widely used where a breathable, long lasting external finish is required.
Can you use Breathable Paint on Interior Masonry?
Yes, and it is often a highly effective paint type for some substrates. Interior masonry surfaces such as brick, stone, and render can also hold moisture, particularly in older homes, basements, and other rooms where humidity is harder to control.
Using a breathable paint internally helps the wall regulate moisture more naturally, which can reduce condensation and lower the risk of mould growth.
For interior masonry, traditional mineral paints such as lime paint are often a good fit, especially on lime plaster, stone, or other breathable substrates. Clay paint is another useful option indoors, offering excellent breathability and a soft matt finish for bedrooms, living spaces, and older interiors that benefit from gentle humidity control.
Breathable Masonry Paint - Helps Walls Dry Naturally
Not all masonry paints are designed to let walls breathe. Many standard plastic based coatings prioritise water resistance but restrict the movement of moisture vapour. They might even say breathable on the tin - but they’re not!
Choosing a truly breathable paint allows walls to manage moisture as they were intended to. This helps reduce the risk of damp, improves durability, and keeps finishes looking their best over time.
If you are painting exterior masonry, mineral systems such as Graphenstone GCS Exterior are well worth considering. If you are working on interior masonry, lime paint and clay paint can also play an important role in keeping walls healthy and breathable.
