We have considerable experience in working with cob and in specifying sympathetic repairs. We work alongside conservation officers to achieve mutually agreeable proposals. We can carry out surveys of cob buildings and specify suitable remedial works where necessary.
Dealing with cob is a specialised subject and full specifications for all work on cob is essential, otherwise serious damage and further deterioration can result. For example, if cob is not dampened prior to rendering, the render will not adhere to the cob. Modern cement based renders and paints with limited breathability can result in moisture building up in cob with subsequent deterioration.
Cob is generally a mixture of earth and an contain small stones, straw, hair, manure and various other natural materials. Manure, more often than not, found its way into cob by accident and is not thought to enhance the stability or to be normally intentionally added to the mix. Cob has been used successfully as a building material for many years, but has limited use in the modern world due to financial restraints.
Unfortunately, many cob buildings have been neglected or poorly renovated over the years with many buildings having been repaired with hard brittle masonry re-rendered with sand/cement mixes.
Cob must be maintained at the correct moisture content for stability and must be able to breathe inside and out to prevent excess moisture building up and becoming trapped in the walls. This was originally achieved by utilising breathable materials such as lime renders and lime wash coatings.