Preliminary Roost Assessment For Developments

Preliminary roost assessments (PRAs) are undertaken on development sites in order to assess an area for its suitability for bats to roost, forage and commute. These assessments are typically used to inform a planning application to obtain planning permission.

A preliminary roost assessment will typically be required by a local planning authority when it is determined that a proposed development may impact its surroundings or obstruct access to a space that bats could be residing in.

Preliminary roost assessments are undertaken in buildings, structures or trees to help determine potential bat presence. These assessments may also be undertaken as part of a preliminary ecological appraisal on a development site.

Bats are protected by law in the UK by both domestic and international legislation, making them a protected species. Therefore, if these assessments determine that bats may be present in the area, bat mitigation and compensation measures must be undertaken before any development work can begin.

bird surveys

Types of bats found in the UK

There are many species of bats which are likely to be found in the UK. These include common pipistrelle bats, Noctule bats, soprano pipistrelle bats, Daubentons’ bats, Whiskered bats, Brandts’ bats and Nathusius’ pipistrelle bats.

A specific species of bat in an area can be determined by examining a DNA sample found in bat droppings as part of a preliminary roost assessment (PRA).

Undertaking preliminary roost assessments

Unlike other types of bat surveys, preliminary roost assessments can be undertaken at any time of year. These assessments typically coincide with a desk study which aims to review and collate existing information about the development site and its surroundings. Ecological records will be examined to establish whether there have been indications of bat presence previously.

For buildings and structures, both an internal and external assessment should be undertaken. This will usually include an examination of any boiler rooms, cellars or loft voids. Any access points into the building will also be noted for any signs of bats. Evidence that could lead to an indication of bat presence that bat surveyors will look for include feeding debris, bat droppings and features that may accommodate roosting bats.

Preliminary roost assessments for trees are often more conclusive when undertaken from a higher level. This is because features suitable for roosting bats can often be difficult to assess from ground level.

The outcome of these assessments will provide a suitability category for roosting bats once surveys are undertaken. These categories include negligible, low, medium and high. Negligible suitability means that no further bat surveys will be required meaning the planning application can proceed. Low, medium, and high categories will generally require further bat activity surveys to establish bat presence and whether mitigation methods are required.

It is strongly recommended that an ecologist is employed to provide assistance when conducting a preliminary roost assessment. Experienced ecologists can also provide guidance on mitigation measures that may need to be taken and can design any necessary mitigation plans.

How can Collington Winter assist with preliminary roost assessments?

Collington Winter Environmental are a team of ecological consultants with many years experience in undertaking bat and hibernating bat roost assessments on all types of development projects and can meet any bat survey requirements and record bat presence. Our Ecology Director, Olivia Collington, holds a Natural England Bat licence and has worked with protected species and bat surveyors across the UK.

Please contact our Ecology Director Olivia Collington ( for more information on our ecological services and protected habitat surveys and species survey work, including bat surveys and great crested newt surveys. We also provide ecological appraisal and assessment services.

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