Choosing the right exterior paint is not just about colour or weather resistance. For many homes, particularly older properties, solid wall buildings and eco builds, breathability plays a vital role in keeping the building healthy and regulating moisture.
Moisture moves naturally through materials such as brick, stone, lime render and timber. When the wrong paint is used, moisture becomes trapped behind the coating. Over time this can lead to flaking paint, persistent damp patches, surface damage and, in some cases, long-term structural issues.
The term “breathable paint” is used widely in paint marketing, but it’s not a regulated term. That means not all paints that claim to be breathable will be right for buildings that need true breathability. This guide explains what breathable exterior paint really means, and why it matters.
What Is Breathable Exterior Paint?
Breathable exterior paint, is designed to allow moisture vapour to pass through the paint film rather than becoming trapped beneath it. This supports the natural moisture regulation of walls and timber, which is how many traditional materials are designed to function.
True breathable paints are typically made using mineral or natural binders such as lime, silicate, plant oils and natural resins. These materials form a protective coating that repels rain while still allowing internal moisture to escape.
The only reliable way to understand how breathable paint is to review the technical data rather than relying on what it says on the paint tin.
SD Values Explained
The most reliable way to assess whether a paint is genuinely breathable is by checking its SD value on the technical data sheet.
The SD value measures how much resistance a coating provides to water vapour passing through it. Lower values indicate higher breathability.
- Under 0.1 is considered highly breathable.
- 0.1 to 0.5 is generally suitable for traditional buildings and solid walls.
- Above 0.5 may begin to restrict vapour movement and increase the risk of trapped moisture.
For lime render and other highly vapour open substrates, only paints with very low SD values should be used.
The word “breathable” on a label has little meaning without supporting technical data.
Breathable Paint for Masonry
Masonry surfaces such as brick, stone and blockwork need protection from driving rain without being sealed beneath a plastic film. This is especially important on solid wall buildings and properties built with lime mortar, where moisture must be able to evaporate naturally.
The breathable masonry paint we recommend for exterior performance is:
Earthborn Silicate Masonry Paint
A mineral based potassium silicate paint designed for vapour open substrates and heritage buildings. It forms a permanent chemical bond with mineral surfaces rather than sitting as a surface film.
Earthborn Silicate Masonry Paint is:-
- Highly breathable with an Sd value of 0.06 m.
- Very low VOC content at < 0.5 g/L
- Suitable for renovation of historic buildings, including lime based substrates.
- Weather resistant, washable and colour stable.
- Biodegradable with appropriate disposal guidance.
- Also suitable for interior use.
Earthborn exterior masonry paint makes it a strong option for those who want durability, genuine vapour permeability and credible environmental performance, rather than marketing-led claims.
Breathable Paint for Lime Render
Lime render is one of the most vapour open materials used on external walls. To function correctly, it should be paired with a paint that offers exceptionally high breathability. Using conventional masonry paint on lime is one of the most common causes of trapped moisture and render failure.
The lime compatible systems we recommend are genuinely mineral and vapour open by design.
AURO High grade Lime Paint No. 344
A traditional lime paint made from calcium hydroxide. It is specifically formulated for mineral substrates and is highly suitable for lime render on exterior walls.
Auro 344 is:-
- Exceptionally breathable with an Sd value of < 0.05 m.
- Virtually no VOCs (product VOC: 0 g/L).
- Made using a consistently ecological selection of raw materials.
- Naturally anti-mould due to the alkalinity of lime.
- Purely mineral formulation, fully compatible with traditional lime systems.
- Suitable for untreated, absorbent exterior mineral substrates.
Lime Earth Lime Paint
A lime based paint system suitable for both interior and exterior mineral surfaces including lime render, brick, stone and plaster. Very close in performance and characteristics to traditional limewash paints.
Lime Earth paints offer:-
- A mineral, vapour open structure.
- Natural mould resistance through alkalinity.
- Suitability for exterior use on breathable substrates.
- A range of natural earth pigments for softer, traditional finishes.
Formulated to be more durable than traditional limewash, with enhanced freeze thaw durability. Lime Earth is a modern twist on a historically accurate paint type.
Breathable Paint for Wooden Windows and Exterior Wood
Exterior timber needs to release moisture as humidity and temperature change throughout the year. When wood is sealed beneath non breathable petrochemical paints, moisture can become trapped, leading to cracking, peeling and eventually timber decay.
Our recommended exterior wood paints offer true breathability for exterior wood, low emissions, responsible ingredients, without compromising on performance.
AURO COLOURS FOR LIFE Satin Paint No. 517
A water thinnable, solvent free opaque wood finish suitable for interior and exterior use, offering a durable satin to eggshell style finish with strong eco credentials.
Auro 517 is:-
- Very low VOC (product VOC: <= 1 g/L).
- Solvent-free and without added wood preservative.
- Natural ingredients include mineral pigments and plant derived surfactants.
- Available in white and a range of colours
AURO COLOURS FOR LIFE Gloss Paint No. 516
For those who prefer a higher sheen finish on exterior woodwork, AURO 516 offers the same environmental and safety credentials in a gloss format.
Auro 516 is:-
- Very low VOC (product VOC: <= 1 g/L).
- Solvent-free and without added wood preservative.
- Available in white and a range of colours, suitable for both heritage and contemporary schemes.
These finishes are designed specifically for wood and wood-based materials, supporting a healthier approach to decorating through low emissions and independently verified safety testing.
Best non toxic exterior wood paint options: AURO 517 Satin for a lower sheen finish, or AURO 516 Gloss for higher shine. Both are solvent-free, very low VOC (<= 1 g/L).
Frequently Asked Questions About Breathable Exterior Paint
Frequently Asked Questions About Breathable Exterior Paint
How can you tell if paint is breathable?
The only reliable way to tell if a paint is truly breathable is to check the technical data sheet. Look for the SD value, which measures resistance to water vapour. Lower values mean higher breathability. As a general guide, paints with an SD value under 0.5 are considered suitable for traditional buildings, while values under 0.1 indicate very high breathability. Marketing terms such as “breathable” or “vapour open” are not regulated and should not be relied on without supporting technical data.
Does masonry paint cause damp?
Masonry paint itself does not create damp, but non breathable masonry paints can trap moisture inside walls, which can make existing damp problems worse. On solid wall buildings and older properties, moisture needs to evaporate naturally through the wall. If a plastic-based paint restricts vapour movement, moisture can build up behind the coating, leading to damp patches, blistering and flaking.
Do you need breathable paint for brick?
Breathable paint is especially important for older brickwork. Using a vapour permeable paint helps prevent trapped moisture and supports the health of the brickwork. Newer cavity wall buildings may be more tolerant, but breathable paints are still a safer long term choice.
Is wood paint breathable?
Some wood paints are breathable, but many conventional gloss and exterior wood paints form a sealed plastic film. This can trap moisture in timber and contribute to cracking, peeling and rot over time. Breathable or vapour open wood paints are designed to allow timber to release moisture while still providing weather protection, which supports healthier, longer-lasting exterior joinery.
The Importance of True Breathability
Choosing the right breathable paint helps preserve the structure of the building and supports the way traditional materials are designed to perform.
A truly breathable paint helps maintain the health of masonry, lime render and timber, supports better moisture balance throughout the building, and reduces the likelihood of recurring decoration problems.
Need advice about the best breathable paints for your next project? Contact Us - our friendly team of paint experts will be happy to help!
