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Is masonry paint breathable?

We get a huge number of enquiries about masonry paint, and whether it is breathable.

The short answer is NO.  And NO again.

Masonry paint is NOT breathable.  The paint companies will tell you it is, but the bottom line is that anything made with plastic is not breathable.  You wouldn't take your house out for a run in a plastic mac would you?  It sweats.  

Wataerproof masonry paint is a bit of a problem as a concept.  Counter intuitive maybe - but old houses need to breathe.  If you slop any form of plastic onto an old building, it will not be able to breathe.  That starts to cause huge problems with moisture retention in the building fabric.  When that happens, your masonry paint, that you thought was breathable, starts to peel and flake.  Why?  Because water vapour pressure is pushing it off the wall.  Precisely because it is acting like bubble gum. Blow hard enough, the bubble grows, and then bursts... pop.  And so the masonry paint pops and blisters as moisture finally manages to get out.

The worst culprit by far is Sandtex masonry paint.  We have seen this again and again - thick layers of Sandtex built up over years of painting an old house, until it forms a horrible thick plastic sheet.  Eventually it is so thick that you can lift an edge and peel big sheets off it - sometimes water actually runs down behind the paint sheet.  When peeled off, the sopping wet wall behind will gradually start to dry out.  I've seen old solid walled houses with Sandtex masonry paint covering them that have taken 18 months to dry out when the Sandtex was removed.  My advice - steer clear of ANY masonry paint.

If you want truly breathable external paint - there is only one thing to use - Limewash. It's been used for hundreds of years, and it WORKS!  It's a shelter coat - protection for a wall.  It is breathable.  It lets moisture in and out.  It is amazing stuff. Most of the lime companies - folk like Ty Mawr for example, sell limewash.  It comes in an amzing variety of colours.

If you are looking to paint INTERNAL walls, use the Earthborn clay paints - they are superb.  DO NOT use proprietary emulsions, and so called breathable, or washable acrylic anything.. It is not breathable, and will trap moisture into the wall.

Peeling masonry paint from the wall of a Grade 2 Listed building which was sopping wet.  Once removed, the building dried out rapidly.

Here youo can actually see water running down behind the paint as it was peeled off - this water was being foced into the wall, making it wet and cold.  Once the paint was removed, the wall dried out very quickly.

Our client removing masonry paint from the wall of his Listed building.  It soon dried out.  He is guilty of introducing me to Nick Price - who runs Two Clicks web development, and is responsible for the design and running of this website!

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