BCD SPECIAL REPORT ON
HISTORIC CHURCHES
21ST ANNUAL EDITION
17
encourage bats to move away from sensitive
areas in churches. It is here that the report
is perhaps disappointing, as this area of
work is touched upon only lightly. The
report states that bats were not observed
using alternative roosts during the relatively
short experimental periods (although some
limited use was observed subsequently), and
that the adoption of bat boxes is dependent
upon many factors and may take several
months or years. The provision of alternative
accommodation for bats is an effective way
of managing bat colonisation, and it is to
be hoped that Defra will consider further
research in this area to identify possible
solutions for building custodians.
From the conservation professional’s
perspective, perhaps the best approach to
coping with bats in a historic building is simply
to follow the principles that underlie all sound
conservation: work with the existing building
and traditional materials to see what measures
are possible before considering more invasive
or architecturally inauthentic techniques.
Traditional handmade clay tiles, for example,
are a far more suitable alternative to machine-
produced tiles as they contain enough
dimensional variation to accommodate bats
within the outer roof layer without damaging
the internal fabric. On older buildings, putlog
holes (small holes in external walls to support
the original timber scaffolding) create a void
for bats and repointing work can retain a small
gap for bats to continue accessing a roosting
space within the external fabric. Martin
Ashley Architects has used this and similar
techniques successfully on church buildings
and elsewhere, including at Hampton Court
Palace where tile slip vents (above left) can
be used to provide roosting opportunities.
Eaves and soffits provide attractive bat
roosting spaces, and insect mesh can be fitted
slightly further back in the building envelope
to prevent them from accessing further into
the building while allowing ventilation. At
Kew Palace Kitchens, ventilating details were
specially designed to allow bats to roost
within the external fabric while protecting
the building interior, a technique that is
readily adaptable to church buildings.
Efforts to provide alternative roost
accommodation for bats are certainly
worthwhile and greater research in this
area may prove useful to custodians and
conservators alike. When re-roofing the
Canons’ Cloister at St George’s Chapel,
Windsor Castle, for example, bats were
discovered only once the building had been
scaffolded and a series of soffits removed.
Work was stopped in the specific location until
a series of new bat boxes had been designed
and installed at intervals along the length of a
new eaves section. As these were not ventilated
into the roof void they remained dry and
draught-free. Bats were further encouraged
to inhabit these new spaces by scattering the
droppings, which had been found when the
soffits were removed, into the new boxes.
Other projects allow greater freedom
to create ‘bespoke’ bat accommodation: at
Brockham Lime Kiln in Surrey, for example,
a collapsed kiln was specially rebuilt with the
Brockham lime kiln, which was rebuilt for Surrey
Wildlife Trust to protect local bat colonies
A tile slip bat access vent
help of historic brick specialists to encourage
bat colonisation. It was a challenging project
not only to design complex brickwork but
also to avoid disturbing bats present in
neighbouring structures, a scenario that exists
in dark and peaceful church crypts across the
country. At both projects the end results were
very successful, but would certainly not have
been possible without the co-operation of
the project teams and the valuable expertise
and advice of experienced bat surveyors.
Any measures to accommodate or
manage bat colonisation in churches will
need to take a wide range of issues into
account such as the demands of particular
species, existing roosting positions, the
availability or potential of alternative roosts,
and roosting cycles. Getting pre-emptive
surveys and accessing good specialist advice
is always paramount. Based on the University
of Bristol research, further research and
product development are underway in the
field of acoustic deterrence to address bat
colonisation inside church buildings.
In addition, further work should be
done to highlight how existing fabric and
traditional techniques or materials can address
colonisation. Bats can be accommodated,
but more can be done to assist custodians
in addressing the challenges that they bring.
More importantly, Bristol University’s research
suggests how and where the legislation
could perhaps be targeted more effectively.
Recommended Reading
Bats in Churches: A Management Guide,
Natural England, 2011 (all Natural
Bat Mitigation Guidelines, Natural England,
2004
Bat Surveys: Good Practice Guidelines, 2nd
Bats in Traditional Buildings, English Heritage,
K Gunnell, ‘Conserving Bats and Buildings:
A Natural Synergy’, The Building
Conservation Directory, Cathedral
M Zeale et al, Improving mitigation success
where bats occupy houses and historic
buildings, particularly churches, Defra
ANDREW HARRIS
is an associate at Martin
Ashley Architects
)
and an architect accredited in building
conservation (AABC). His experience ranges
from small churches to nationally significant
buildings including Hampton Court Palace
and St George’s Chapel, Windsor. He is a
regular speaker and site tour leader.
Hanging clay tiles above a dormer window at
Hampton Court Palace were discreetly raised in one
corner to allow bats to access the roof space.
