/ Justin Fenton / Conservation

Two dark shadows hang over our conservation work; asbestos and rot. Asbestos is a consequence of collective historical handiwork, where the building and product industry pushed the edges of technology to create a versatile and incredibly useful material that we found ultimately to be a silent killer. Rot is nature's killer, not of people but of the fabric of our buildings. Albeit without the health consequences for us, the impact of rot's silent creep is from an economic and disruption stand point, extremely significant.

Much documentation work has been carried out in arming ourselves against rot in buildings including a joint document by Historic Scotland and English Heritage on timber decay in buildings, Rot in Timber by Historic Scotland, BRE codes of practice 299 and 345 and SPAB documentation.

Various treatments are acknowledged provided by a number of professional companies.

There is the so called orthodox approach namely flooding the infestation with fungicide with the consequential troubling consideration of whether there are environmental issues in using so much fungicide in our buildings. Then there is a more environmental approach, finding the causes of rot by isolating the sources of water and opening up the affected area to let the air at the outbreak. This is easier perhaps in a more public situation but less so in a domestic one where the drying out time often makes this approach prohibitive. Finally there are more pioneering approaches such as biological control but they are at an early stage of development.

So how do we deal with it? Firstly you have to unusually, get a feel for it within the building. It has a distinctive smell of mushrooms which is hard to forget. Sniffer dogs are often used to detect outbreaks but experienced operatives are needed, if only to interpret the barks. The initial fabric report, with technical support from rot specialist companies, is crucial in establishing the extent of the situation.

Secondly, the areas of infestation should be opened up as much as possible - allowance should be made for this as soon as is practicably possible. In parallel, the nature of the construction and history of repairs can be established through this process.

Thirdly, when reaching the billing stage, allow for a thorough survey, if not already undertaken, and include allowances set at the pessimistic level.

Then, when it comes to treatment, prioritise the removal of the water source and provide that key ventilation particularly to lathe and plaster walls, remembering that it takes approximately one inch per month to dry out traditionally constructed masonry walls. Check that the contact between timber and the damp source has been eliminated and remember that using the environmental approach requires time for drying out. If employing the orthodox methods of elimination ensure you obtain guarantees.

However, the best way to deal with rot is to eliminate the possibility by regular maintenance and vigilance, and to remove any possible source of moisture which could create the conditions for the rot to develop in the first place.