Why painting your house could damage it.

Masonry shouldn't be painted, certainly when it comes to solid-walled properties. The paint, often plastic-based, traps moisture in the walls. Damp specialists often refer to rising damp or penetrating damp when most of the time it's better being viewed as trapped moisture.

Plastic paint on brickwork, partially removed.

Moisture will always find a way into your walls, both internally and externally; it then takes the path of least resistance to escape. A fresh coat of paint on the external wall will likely push it out on the inside. Tanking is often the next attempt to stop it; this will then push the moisture up or out of the easiest coating to break through.

Masonry that is kept damp for long periods of time will drastically decay; the bricks or stone will become soft and break apart. Painting your house could lead to massive costs in the long run; removing the paint is a specialist job, and DOFF is often the best course of action. Once the masonry has decayed past a certain extent, the paint will need removing, and it could either need rendering or limewashing to protect it. Aggressive and abrasive methods should be avoided; sandblasting will easily remove the face of the brick, leaving it more permeable so it acts like a sponge.

DOFF paint removal.

Many coatings are labelled as "breathable" and yet also claim to be water repellent; some of these companies will also try to back up their products with a low SD value; these are often false. Solid-walled properties need to allow moisture to move freely, so it's not possible for any water-repellent coating to be breathable in the necessary way. Traditional coating should be the only viable option; limewash and good-quality clay-based paints are the best options. A traditional limewash is the cheapest option, especially so when being made on the job.

The paint used inside your home will also have similar effects, especially if lime plaster is still present. Breathing, cooking, and showering will release moisture into the air; ventilation is important, but the coatings on your plaster can fail if inappropriate. Again, it's worth remembering that paint is often mislabelled as being appropriate for use with heritage properties or labelled as conservation friendly, It's best to stick with materials that would have been used when the house was first built.

Plastic paint peeling away after moisture breaking through inappropriate plaster.