Where modern impermeable paints have been applied directly to stone or lime plaster on external walls, this will often crack and trap water in the walls. Modern paints are rejected by traditional materials, resulting in the paint bulging or flaking off in large strips.
There are several options available for dealing with paint removal including solvents, poultices and mechanical processes. However, these can be very time consuming, highly labour intensive and expensive.
In our experience, the most effective way to remove paints from the fabric of the building is by using high pressure steam and paint softeners, which remove the paint without damaging the building underneath. This is a skilled task that requires special training as the process can be fraught with problems, such as dealing with the remnants of old lead-based paints and toxic sealants. For this reason it is essential to get a professional to handle the procedure for you.
Sandblasting is generally considered too aggressive as it will take the carbonated surface off masonry and the fired surface off brick, leaving them prone to delamination in winter months, weather erosion and failure.
Following paint removal, lime pointing or rendering may be required. If you prefer a 'painted' finish, go for a limewash coat which is highly breathable and will not damage the structure of the building.