Pest treatment and protected wildlife overlap in loft spaces
Woodworm, cluster flies and wasps are common reasons for treating a roof void, and roof voids are also places where bats roost. This article summarises the Natural England guidance on GOV.UK titled “Bat roosts: use of chemical pest control products and timber treatments in or near them”. The guidance is written for England and was first published in February 2013, and a companion page listing suitable products was last updated in February 2020, so products and formulations may since have changed. Wales, Scotland and Northern Ireland are outside the scope of this article. It is general information, not legal advice.
The starting point: bats and roosts are protected
The guidance states that all bat species, their breeding sites and resting places are fully protected by law. It notes that a chemical product may still be needed in or near a roost, for example an insecticide to control pests, or a timber treatment to protect against insects, fungal growth or weathering.
The central rule is that chemical products cannot be used in or near a known bat roost if bats are present. Before starting, a thorough search for signs of bats, such as fresh droppings, is needed, and the best time to apply treatments is usually between autumn and spring. Householders and places of worship are told to contact the national bat helpline before using a chemical product in or near a bat roost. The guidance describes this as a free service for those groups.
Insecticides
For controlling pests with insecticides, the guidance says to check the list of insecticides to see which products are currently approved for cluster fly, wasp, bee or hornet control, to use products listed for professional use only if the user has the information, instruction and training to do so, and to use the product as directed on the packaging. It also warns about care when treating feral bees so that other working bees are not harmed.
The companion page explains that Natural England is aware of the chemical substances listed for use in or near roosts but does not endorse the products. The lists are therefore a check on suitability near bats, not a recommendation.
Timber treatments
The guidance identifies the timber problems that may need on-site treatment as common furniture beetle (woodworm), deathwatch beetle, longhorn beetle, dry rot and wet rot. Anyone treating timber should check the list of timber treatments to see which products are suitable for use in or near bat roosts, use professional-listed products only with appropriate training, and follow the packaging directions.
Where a product is not on the list, the guidance says to check whether its active ingredients include any of the following: 3-iodo-2-propynyl n-butylcarbamate, benzalkonium chloride, boric acid, copper carbonate hydroxide, dichlofluanid, disodium octaborate, flufenoxuron, permethrin, propiconazole or tebuconazole. If a product contains only one of these, it can be used around bat roosts as long as it is used as directed. If it contains two or more, the guidance says to contact the manufacturer before using it.
Pre-treated timber, stains and preservatives
Timber pre-treated off-site can be used, the guidance says, because the producer injects the chemicals deep into the wood, leaving lower concentrations on the surface that are not harmful to bats. Products used to pre-treat timber should not be applied on-site, because the active ingredients will be more concentrated on the surface and may harm bats. Decorative wood finishes such as stains or wood preservative can be used around roosts if used only on external timber.
What this means when hiring a contractor
The guidance covers both householders and professional users, and it limits products listed for professional use to people with the relevant information, instruction and training. It places responsibility on whoever applies the product to check for bats first, use the correct listed product and follow the label. For a householder, it makes sense to ask a woodworm or insect-control contractor whether they have checked for signs of bats, which products they propose and whether they are on the Natural England lists. A contractor who cannot say what the active ingredients are, or who proposes on-site application of pre-treatment products, does not fit the approach in the guidance.
The right time for treatment is also affected. The guidance says the best time to apply treatments is usually between autumn and spring, so a summer quote for roof-void treatment is worth questioning, particularly if bats may be present.
The bottom line
In England, chemical treatments must not be used in or near a known bat roost if bats are present, and householders are directed to the national bat helpline before using them. Natural England’s lists and its rules on active ingredients, pre-treated timber and external-only finishes are the reference points, and the products are not endorsed by Natural England. Check the current lists before any roof-void or timber treatment.
Sources
- Natural England, GOV.UK, “Bat roosts: use of chemical pest control products and timber treatments in or near them”
- Natural England, GOV.UK, “Bat roosts: insecticides and timber treatments”