Stone Roofs Case Study

There were several stone roofs on the property that had been problematic and always leaked in living memory. Several attempts over the years to treat the problem had failed, causing severe loss of the original internal fabric.

We surveyed each stone roof and noticed that all the cement pointing that had been placed in the 1950’s w had failed with evidence of plant growth and water ingress. The cement pointing had also been placed over past natural weathering drips that had been formed in the stone thus decreasing the natural weathering capacity of the mortar.

We carefully removed all the cement pointing and blew out all loose debris failed mortar with a compressed air line. We then commenced flooding all joints with low pressure cold water and traced all the water ingress inside into the building. The water flooding identified the routes where there were voids, in this case the voids had been formed with water ingress. In addition to the flooding it removed an additional large amount of debris organic material. We then probed the joints and it was over 1000mm deep loss of pointing/bed mortar.

Because of the small fine joins we inserted small diameter grout tubes in the joint intersections. All Remaining areas were plugged with backing rod and an extensive grouting took place. When the grout had cured we removed the backing rods and pointed with a Vapour Permeable Hydrophobic Natural Hydraulic Mortar. The joints were then finished with a Vapour Permeable Hydrophobic Natural Hydraulic Mortar with Improved frost resistance for sky facing joints. This mortar was specifically designed for Castle Drogo in conjunction with Historic England and has proven to be very successful in the application we have used it on.