Need help with a bat?

Follow our advice

or call us on 0845 1300 228

Existing Buildings

Many bats use buildings for roosting, and it is vital for the future of our bat populations that any building or maintenance work takes bats into account from the outset. BLE's against BRM

By taking bats into account prior to starting work you will:

  • Minimise any costs and delays
  • Help to avoid disturbing bats or their roosts, which means you will be avoiding the risk of prosecution and helping to conserve an important protected species.

This section of the website looks at some of issues around bats and building maintenance that may be of help to the building industry and bat workers. These are all ongoing areas of work and will be regularly updated with progress. A summary of the information can be found in the Bats and Buildings leaflet at the bottom of the page.

Practical information:

Find out about the work BCT is doing on:

 Breathable Roof Membranes

Breathable roof membranes (BRMs) have become widely used in recent years. Although originally designed for use as part of a continuous breathable/airtight barrier, they are also used in conventional, ventilated build. There are a wide range of breathable membranes available but it has become apparent, through research undertaken at the University of Reading, that most of these membranes are detrimental to bats.

BCT has been made aware that some manufacturers are reporting their products as 'bat friendly'. This has not been sanctioned by BCT or Natural England. No manufacturer has so far been forthcoming in taking ownership of this claim or substantiating the reasons for it. Further information on this would be useful.

Current situation

BCT has been supporting a research project into this issue through a collaboration with the 'Technologies for Sustainable Built Environments (TSBE)' department of the the University of Reading. Stacey Waring, the research engineer, is due to complete her doctoral work on this topic in December 2013.

The main objective of the research project is to gain an understanding of the impacts of the use of breathable membranes on bat roosts where these occur in roofs and to disseminate the findings and recommendations as a guidance document for use by both the building industry and conservation organsiations.

The planning for this research and methods to be employed are all directly linked to the feedback that has been received from bat workers. For  more information about this project, please visit Stacey's reseach page here.

NEWS: An overview of this issue was published in the new journal Architecture & Environment

Cavity Wall Insulation

It is known that bats use cavity walls to roost in during all seasons. The degree of importance per species and per season is difficult to discern due to the inaccessibility of the structure. Concerns about the carbon footprint of housing stock has led to even greater emphasis on having cavity walls insulated. This has given greater importance to understanding bats' use of cavity walls and identifying suitable mitigation measures where bat roosts are present.

If bats are present in a cavity wall that is scheduled to be filled with insulation a gap should be left for the bats. A difficulty is that leaving gaps in cavity wall insulation can mean that the work may not be subject to guarantee. However, the BBA (British Board of Agrement) has confirmed that partial filling of a Gable Wall is however allowed for blown-in EPS bead certificates. A common statement in them all says:

3.3 Partial filling of the gable apex (i.e. limiting the fill to several brickwork courses above ceiling level) is permitted provided the top of the wall is protected by the roof and:

• the roof void is not an occupied space

• where the loft insulation is at ceiling level.

However, partial filling is outside the scope of BBA approval for blown-in mineral wool (MW) fibre certificates.

Therefore, where a bat roost is found, the property can still be insulated as per the above using EPS bead, but beware that EPS beads are installed using an adhesive. The toxicity of the adhesive to bats is not known at this stage.


Building Regulations

Amendments to the Building Regulations in 2010, largely driven by the need to reduce the carbon footprint of building stock, has at times come into potential conflict with bat mitigation. Questions pertaining to the Building Regulations have been collected and a document prepared, for use by the building industry and bat workers, that attempts to clarify the situation. It is anticipated that document will undergo frequent updates as more situations that require clarification become apparent and as further anticipated amendments to the regulations occur. These changes to the Building Regulations have been implemented in England, Wales, Scotland and Northern Ireland.

Access the new Building Regulations here.

Acess the new Approved Documents here.



BCT is aware that concerns have been rasied over the process for demolitions where they are not part of a planning application. Where this occurs an S80 demolition notice is completed by the applicant and an S81 issued by a Building Control Officer at the local authority. In most cases the S80 form supplied by the local authority does not include a question on protected species and therefore it would seem likely that in many cases the presence of bats could be overlooked.

NEWS: In a judgment delivered on 25 March 2011 the Court of Appeal decided that demolition constitutes a project under the terms of the EU Environmental Impact Assessment Directive. This automatically meant that the directive in UK law which exempts the demolition of certain building types from requiring planning permission became unlawful.

The ruling will have major implications for planning
authorities. More info here.

Case studies

To view or upload case studies of bat roost replacement or enhancement visit Roost.

You should follow us
Bookmark and Share

Subscribe today to receive the latest on bats and BCT direct to your inbox.

Bat Helpline

0845 1300 228