My 1860’s house has solid brick walls that have been covered with a sand / cement render followed by a tyrolean finish. I want to paint them with an exterior emulsion to reduce dampness when the walls are subject to heavy rain. They also have some fine cracks but the render seems essentially sound.
One painter I have spoken too would recommend a water based exterior emulsion, but another favours a solvent based pliolite paint. Would the latter be as breathable? I can’t find much info on breathability of pliolite paint.
What would you recommend?
Pliolite paint is formulated for application when there is a likelihood of rainfall within a few hours. It is, by nature, less breathable than regular masonry paint and has no performance benefits. Any painter who doesn’t know this ought not be allowed within a mile of your property.
It sounds like your walls are taking in a lot of moisture and you really need to address the cause of this first. The fine cracks you mention will need to be properly repaired first. If the walls are still taking in so much moisture it may be worth considering a solution that allows the walls to breathe rather than trying to make them water-tight. The solution to this involves both sides of the walls – not just the outside.
The SPAB publication ‘Breathability & Damp‘ is well worth a read.
Ordinary water based masonry paint is the most economical solution but not ideal.