BCD 2017

150 T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 1 7 allow this to proceed. In some cases it may be illegal to disturb birds that are occupying buildings, for example when they are nesting. However, it is still possible to discourage or manage their occupancy of the building in the first place in a legal and sympathetic way. Similarly, disturbing bat occupancy in buildings is against the law in the UK under the Wildlife and Countryside Act 1981 . This can be rigorously enforced by interested parties and the local authorities, and could lead to a situation where a building becomes unusable due to the short-sighted enforcement of regulations to protect occupancy by bats in the short term. Long-term occupancy of a building by bats is often better managed by making special provision for occupancy using ‘environmental enhancements’ with the agreement of the relevant authorities. This approach may also be used cost effectively in controlling occupancy by birds, for example by providing or refurbishing existing pigeon lofts or providing owl roosts and other enhancements as part of refurbishment and conservation works. Preventing or managing the build-up of guano This can be achieved by modifying the built environment occupied by birds or bats to include specially designed roosting areas. Safe, routine inspection and maintenance, including the routine removal of guano, should also be considered. This should be arranged either to assist in discouraging occupancy where possible, or conversely to prevent disturbance of occupancy where this would be illegal, as could be the case with bats or nesting birds. Suitable specialist cleaning equipment may be needed, such as high-powered vacuum cleaners with medical grade filters. Current health and safety and legal requirements should be considered. While it may be possible to encourage bats to roost in a different part of a building, and thus reduce the effects of urine and droppings on a particular feature such as a church organ, it is more likely that surfaces will need to be protected. The use of sheeting over fixtures and fittings offers a solution but is unpopular with congregations and visitors as it is obtrusive and requires regular cleaning or replacement. Smaller, bespoke covers can be used over certain items, such as altars and lecterns, and these can be designed to co- ordinate with other fabrics in the building. Fixtures and fittings that cannot be covered, can be protected with surface coatings or finishes such as microcrystalline waxes. These treatments need to be carefully selected and applied to avoid changing the appearance of the particular surface and are perhaps best specified by a conservator. Floor surfaces pose a particular problem, as sheeting can reduce moisture evaporation from permeable materials and pose a potential trip hazard. Again, it may be possible to use surface treatments on certain materials as a means of offering protection from urine, but these will need to be periodically removed and re-applied. Removal of guano The removal of guano and contaminated materials from buildings in the UK is estimated to cost over £15 million a year. However, this figure is unlikely to include the costs of ancillary works or remedial works to deal with the consequences of contamination The removal and disposal of guano in buildings is often undertaken by specialist contractors or sub-contractors with appropriate practical experience and the necessary health and safety protocols. However, in the UK there is no legal requirement to employ specially trained or licensed contractors, unless the deposits contain other hazardous materials such as asbestos. Using general contractors for this work is often cost-effective, as the materials can usually be disposed of as ‘general waste’. However, special consideration should be given to decontamination of especially vulnerable materials and structures, as unsympathetic removal can cause more damage than the guano itself. This can be a particular problem if there are decayed substrates, or where materials and finishes are decorated. Specialist conservators may then need to be brought in, at least for the critical cleaning and treatment of vulnerable surfaces. LEGAL, SOCIAL AND CULTURAL CONSIDERATIONS In addition to the Health and Safety at Work Act , the legislation affecting the removal of bird and bat guano from the built environment is the Wildlife and Countryside Act 1981 (Chapter 69) and potentially the Animal Welfare Act 2006 . However, there can be confusion in the UK about what the current legislation allows. This may be because some have interpreted the legislation to support their own agendas; either to prevent disturbance of a particular species at all costs, or to promote the sale of, for example, pigeon-exclusion products. As there have been few if any legal prosecutions or judgements to clarify the situation, it is possible to argue that the legislation precludes any activity that might disturb any species of bird or bat in the built environment. However, closer reading shows this interpretation is incorrect. Indeed, ‘General Licences’ for pigeon control measures and the disturbance and disposal of nests can be granted by the Department for Environment, Food & Rural Affairs or other appropriate statutory nature conservation organisations (SNCOs). These can simply be obtained online from the www.gov.uk website. The law should not prevent a property owner or manager from removing accumulations of guano and preventing future accumulation, provided things are done at the right time and with the correct authorisations. For bats in the UK, this is controlled by SNCOs under the terms of the Animal Welfare Act 2006 . These organisations are: Natural England, which is generally supported by the Bat Conservation Trust working for the local authority planning departments; Scottish Natural Heritage, which provides free advice and free site visits for domestic properties, advising on such things as mitigation; Natural Resources Wales; and the Northern Ireland Environment Agency. However, in the UK and other parts of the world birds and bats may have special emotional significance to some groups. It is therefore always important to be sensitive to this, and it is generally wise to seek specialist independent advice. Further Information E Bernardi et al, ‘The effect of uric acid on outdoor copper and bronze’, Science of the Total Environment , Elsevier, London, 2009 X Bonnefoy et al, Public Health Significance of Urban Pests, World Health Organization, Copenhagen, 2008 (http://bc-url.com/pests) J Hales, ‘Bats in Churches: Objective assessment of associated damage mechanisms’, Archaeology International 17, UCL, London, 2014 (http://doi.org/10.5334/ ai.1703) Health and Safety Executive, ‘Construction Micro-organisms: Psittacosis and other diseases from work involving bird droppings’ (http://bc-url.com/ microorganisms) T Hutton and J Dobson, ‘The control of feral pigeons: an independent approach’, Structural Survey , Emerald, Bingley, 1993 Scottish Natural Heritage, ‘Protected Mammals – Bats’ (http://bc-url.com/bat ) (See also www.handr.co.uk for further information and technical leaflets and articles) TIM HUTTON is a building pathologist and environmental scientist and the CEO of Hutton + Rostron Environmental Investigations Ltd (H+R) (See page 143). DAVIDWATT is a chartered building surveyor and historic buildings consultant, working as associate director with H+R. JENNY BROWN is a historic building surveyor and assistant marketing manager at H+R. Pigeon guano accumulation in an abandoned building which aided the growth and spread of timber decay in the floor structure (Photo: Jenny Brown)