Purpose-built roosts

Bat boxes

Although bat boxes are usually inappropriate substitutes for bat roost features in buildings (especially for features such as roof voids) they can sometimes be used for small-scale or supplementary mitigation.  Where bat species are roosting in features such as narrow wall cavities, behind hanging tiles and underneath wooden cladding, some types of boxes may provide an appropriate form of mitigation. In these cases, the boxes should provide similar environmental conditions to the original roost features (e.g. permanence, height, aspect, and thermal regime).

Bat box designs which have been used successfully include integral wall boxes (such as those produced by Ibstock and Ecosurv), pole mounted boxes (such as those based on designs in the USA) and boxes installed in roof spaces (such as designs proposed by Scottish Natural Heritage in A Review of the Success of Bat Boxes in Houses - Report 160).

It is important that the type of bat box should be appropriate to the species. The most frequently used bat boxes are only suitable for crevice-dwelling bat species. Large, carefully designed boxes inside buildings can be constructed for species such as horseshoe bats and serotine bats: these require particular attention to bat access and position within the roost environment.

Please consult the BCT webpage on Bat Boxes to find out more about the different types of bat boxes, including those used for new build.

Bat houses and barns

Maintaining roosts in-situ is always the preferred option. However, in some cases purpose-built bat houses or bat barns may be considered, as long as the risks of non-adoption by bats are minimised through careful design and site selection.

Below are some design principles for ex-situ roost conservation. Please consult the Bat Mitigation Guidelines for more detail.

  • Situate the replacement roost as close as possible to the roost to be lost
  • Match the replacement roost closely in terms of size, height and aspect
  • Situate the replacement roost close to existing flightlines and have an entrance close to appropriate habitat, to maximise chances of the bats finding and adopting it
  • Design the new roost to provide a suitable thermal regime for the target bat species
  • Provide a variety of roosting opportunities and thermal regimes
  • Make the building resistant to vandalism
  • Arrange for the long-term integrity and security of the replacement roost