Inspections and surveys for biodeterioration

Historic buildings such as churches, abbeys, castles and monuments, with beautiful ornamental architectural and decorative finishes, represent the depth of our cultural heritage. Deterioration problems in these buildings are attributed to environmental conditions favouring the decay of materials and contents, such as water, humidity, temperature and lack of ventilation.

Sympathetic and careful investigatory techniques of these buildings can help to keep the original decorative and architectural features. Carrying out non-destructive inspections of hidden cavities on historic buildings requires specialist equipment and techniques and a good knowledge of building materials, environment and construction. Until recently the only specialist non-destructive inspection equipment was an endoscope.

Environmental Building Solutions has pioneered the use of an air sampler for carrying out non-destructive inspections of hidden cavities and voids in historic buildings. This machine extracts a known volume of air from a hidden void or cavity through existing holes in the fabric or through small holes made discreetly. The collected sample can then be analysed for, for instance, dry rot, wet rot and mould spores. Normal background levels of spores would indicate a low risk of decay; high levels would indicate a problem in the void that can then be followed up using fibre optic inspection and Resistograph decay detection drills to investigate hidden timbers.

The Resistograph is a device based on the drill resistance measurement principle. The measurement accuracy can even detect the differences in the density of early and late sapwood. The drill canal is so fine that the drill shavings remain in the wood and almost no air can enter the wood, which minimises the decay infection.

Examples of successful case studies include Hampton Court Palace, Tower of London, Pacific Wharf flats, Wandsworth tower blocks, banks building at Canary Wharf, Belgrave Sq buildings, St James Sq Buildings, Norwich Union headquarters building, Westminster Abbey, Passenham Manor, Harrow School, Deal Castle, Windsor Castle and Dover Castle.

Figure 1: Air sampling of a historic void behind decorative finishes

Figure 2: Resistograph inspection of the historic structural timbers

Figure 3: Resistograph print out of a truss in a church showing timber decay

Figure 4: Resistograph print out of a truss in a church showing sound timber with no timber decay