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Chimney Repair using Stormdry - Denne House

A chimney stack on a Grade II* listed building in West Sussex was suffering from penetrating damp.

Damp was appearing on the internal chimney breast of an upstairs fireplace. A survey revealed that water had penetrated through the sandstone and brick construction of the chimney stack, and down to the internal wall.

The chimney had small visible cracks in its external brickwork and failed mortar joints. In addition the flaunching had previously been repointed with an inappropriately strong sand/cement mix, which had subsequently cracked. This had not directly affected the masonry, but had allowed a sapling to take root and cause further damage to the flaunching. Sandstone had been used for some of the construction, which was also permitting water ingress.

To repair the chimney a wire brush was used to lightly remove any surface dirt and moss, leaving the underlying masonry surface unaffected. The defective flaunching and vegetation were fully removed and loose mortar chased out by hand. Repointing work was carried out using a suitable hydrated lime and sand/cement mix. Repairs were also made to any visible small cracks and defects. Once completed the new repointing was left to cure for one week. Stormdry was then applied by brush in a single coat. The flaunching, brickwork, stonework and flues were all fully treated with the water-repellent cream.

Stormdry penetrated the brickwork and stonework within a few hours, where it cured and formed a water-repellent barrier. This is an in-depth treatment that goes past surface cracks to give increased water resistance. The brick and stonework remain “breathable” though and water vapour can still pass through.

Once cured the Stormdry coating lightens to the original matte appearance of the brick and stonework, and there is no visible difference to before the treatment. The character of the chimney is preserved and no rebuilding works are required.

The water ingress to the apartment chimney breast was successfully stopped, and the chimney stack is protected from future damp penetration. The building manager said he was “very pleased” with the finished works and the performance of Stormdry.