The inspiration for this blog is quite literally, much closer to home than most other blogs! During some proposed renovation works to weatherboarding on the front elevation of my house, it has become apparent that we have bats roosting behind. All of our members will be aware that bats and their roosts are protected under The Wildlife and Countryside Act 1981 (as amended) and The Conservation of Habitats and Species Regulations 2010 (as amended). As preservation surveyors (especially those working in rural areas), the likelihood of us coming across a bat roost at some point of our career is quite high.

To avoid an offence from being committed, if bats are known to be or have been present, or bats or their droppings are discovered at any stage (including after operations have started), work must not commence or must stop immediately and advice be taken from the Statutory Nature Conservation Organisation (SNCO).

As a preservation surveyor if you are going to stumble across a bat roost, it is likely to be in a loft void and whilst looking for evidence of wood boring insects.

Treating the infestation of wood destroying insects

The use of timber treatment chemicals in roofs to control for woodworm used to be responsible for the deaths of whole colonies of bats. Since the problem has been recognised, many products have become available that are more suitable for use in bat roosts to treat the timber and to treat infestations.

Prior to undertaking any form of treatment it is essential to establish if the infestation is active, or historic. All timber should be investigated by a suitably qualified person to determine evidence of current activity to justify any form of treatment. Some timbers may show signs of historic activity. The insect may have already died out due to unsuitability of the timber, decreased moisture content or due to previous treatments – therefore treatment is not justified.

Two of the more notable woodborers found in UK buildings are Common Furniture Beetle (Anobium punctatum) and the Deathwatch beetle (Xestobium rufovillosum).

The Common furniture beetle is the most abundant of the wood destroying insects found in buildings in the UK. It naturally inhabits dead stumps and fallen branches in woods and hedgerows, but is more abundant in building timbers and furniture. One of the most distinguishable indicators of an active infestation by this beetle is trails of fresh bore dust particularly on vertical surfaces. Other indicators include the presence of adult beetles, larvae in the timber, and holes with a fresh cut appearance.

Due to its preference for certain partially decayed hardwoods, principally oak, Deathwatch beetle is most commonly found in historic buildings. The best indicator of an active infestation by Deathwatch beetle is the presence of adult beetles, which are typically found on surrounding floors.

PCA’s Professional User of Biocides Register

Even if bats are absent from the roof space there is still the chance that they will move in in the future, and we therefore recommend that only a fluid suitable for use in bat roosts is considered; typically based on boron, permethrin or cypermethrin. These treatments have a much lower level of active ingredient than formulations in the past – although all insecticides or herbicides maybe harmful to bats so care must always be taken when using them, and exactly why you should be using experienced users such as those on the PCA Professional Users Biocide Register.

The correct amount of pesticide should be used and treatment should be kept as localised as possible. Since recommendations change regularly, details of insecticides and fungicides can be obtained from SNCOs.

A responsibility to protect bats

In my experience I can not deny that the presence of bats has made undertaking essential remedial works more complicated. However bat numbers across the UK have been in decline for many years, predominately due to a loss of their natural habitat, and we as responsible contractors should be doing all we can to prevent this happening any further.

Whilst protecting a natural environment should be enough incentive to take the correct steps, if its not, then the substantial fines that have been issued certainly will be!

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