Masonry paint applied to stone work is can be for a number of reasons. However, most often, it carried out as a cheap or economical fix. Usually masking a problem, and in so doing, creating a bigger one.
What do we mean?
Certainly at one time, painted masonry was fashionable, and had some limited practicalities. For example, it provided a bright, clean finish! It also allowed algae and dirt to be manually cleaned off more easily before the advent of suitable washing methods. It could provide weather protection to buildings that regularly received strong winds and rain, such as coastal areas.
However with porous stone (such as sandstone) paint traps water, not allowing it to evaporate. This particularly true in cases where the painted areas meet with unpainted areas. Such as in the image shown. A wall meets a gate pillar, but only the pillar was painted, meaning water could move from the wall to the pillar, and then not be able to escape. Over time, this chemically dissolves the stone. Yet, the paint can mask this problem for a time, until the stone crumbles from behind it. If the paint is removed before this can happen, water can escape then through evaporation. The same is true if the stonework meets damp ground, or one area of the stonework is colder or in shade. The principles of water evaporation and condensation apply.
Paint is also often applied to mask cheap or ugly repair work. Perhaps what was once a lime mortar joint has been replaced with ugly cement. Or a stone has been swapped out with a different or inferior replacement. One may elect to cheaply paint over this issue, rather that incur a more costly, but appropriate repair.
One thing is certain, paint on porous stone work will inevitably lead to problems. Sooner or later.
What about paints that claim to be breathable? That claim may be true. However it is much the same as if you wear a water proof jacket on a damp, warm day. Whilst the jacket may claim to be breathable, you will still sweat much more than if you weren't wearing it. How dry you feel is to do with rate of evaporation. If the stone meets an area where it can draw in water, such as from the ground. Paint will always act as a barrier to the rate of water evaporating. It should be noted that modern paints are very different from Traditional Whitewash! However we will discuss that in another article.
Paint removal can be carried out with the underlying stone left in tact. Contact us to discuss options.
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