Page 28 - Historic Churches 2013

28 BCD Special Report on Historic Churches 20th annual edition CATHEDRALC O M M U N I C A T I O N S
during summer months and increasing in
winter months. Extreme weather patterns
are also a concern, with 2012/13 seeing
periods of drought followed by floods and
one of the coldest winters on record.
It is clear that historic buildings in the
UK need to be well prepared for extreme
weather conditions, including exceptional
wind strength and intense rainfall and
snowfall. Quinquennial inspection reports
should reflect this by recommending shorter
time periods within which repairs become
urgent and all churches should keep extreme
weather conditions in mind when carrying out
routine maintenance. The consequences of
failure are not only greater expense in the long
term, but also substantial losses of heritage.
JONATHAN TAYLOR MSc IHBC is joint editor of
Historic Churches.
Simple rainwater chutes on the 14th-century church
tower of St Thomas a Beckett, Box, Wiltshire, (above)
and spectacular gargoyles of the late 15th century at
North Petherton, Somerset (below)
A fine example of a lead hopper on a church tower
near Chippenham, Wiltshire, enriched with cast lead
coats of arms and dated 1725
Late Victorian cast iron gutters and downpipes at the
Church of the Holy Cross, Tramore, Northern Ireland,
with a new section cast to match the original on the
left, and repaired section on the right (Photo: Alumasc)
A new stainless steel chute from a parapet gutter
feeding into a cast iron hopper: the front edge is
lower than the sides so that, if blocked, rainwater is
projected clear of the walls below, avoiding ponding.
A defective ‘ground gutter’ in a Somerset church: blocked
soak-aways, pipes that miss drains and damaged
runs are common defects (Photo: Chedburn Dudley)
Principal issues include:
• ponding, usually caused by blocked gutters
or valleys
• tile or lead slippage due to inadequate or
decayed fixings.
Other problems include:
• wind damage causing metal roof coverings
and flashings to lift
• stress cracking in lead due to thermal
expansion and contraction, often connected
with poor specification or age
• lead corrosion caused by acids leaching
from bird droppings or oak
• spalling roof tiles due to frost damage, often
under the lap
• incidental damage to the roof covering due
to the failure of other components
• accidental damage by, for example, heavy
boots or clumsy workmanship
• ice blocking gutters and chutes causing
overflows from snow melt
• lead theft.
RAINWATER DRAINAGE SYSTEMS
The earliest roofs had broad eaves to project
rainwater clear of the walls. However, with
the introduction of parapets, the water
had to be channelled behind the parapet in
lead-lined gutters then out through a chute
which projected clear of the wall. The chute,
if constructed in stone, provided the medieval
craftsman the ideal opportunity for carving a
terrifying beast or demon disgorging rainwater
from its open mouth – the gargoyle.
Both open eaves and chutes rely on having
well-drained ground around the church to take
the water away, and work best in conjunction
with a French drain. In essence this is a
drainage trench around the base of the wall
filled with free-draining gravel or chippings,
preferably with a field drain at the bottom to
conduct the water away from the building.
Lead hoppers and downpipes were
used on the Tower of London as early
as 1240 to protect its whitewashed walls
from spray, and it is likely that they were
used on churches at around the same time
as an alternative to gargoyles and other
rainwater chutes. The downpipes connected
with drains or ran into ‘ground gutters’
(drainage channels) at the base of the wall.
Eaves gutters could be created using
timber boxes fixed to the ends of the
rafters and lined with lead. However, the
timber required regular maintenance and
replacement, and many medieval rural
churches may never have bothered with them.
It was not until the rise of cast iron in the
late 18th century that the modern system of
gutters and downpipes eventually emerged.
The development offered a much simpler
alternative to bespoke leadwork, and was
robust and far easier to install, and by the
mid-19th century these systems predominated.
Below ground, drains usually run to
soak-aways which become silted up over the
years, as do French drains. Ground gutters
were usually paved and are prone to changes
in level due to plant growth and settlement,
and rarely work as intended. Both lead to
increasing moisture levels around the building.
Faulty rainwater disposal can lead to
saturated walls and erosion of the mortar
pointing, as well as frost and salt damage to the
masonry. In addition to keeping downpipes,
hoppers and gutters clear of debris, inspections
should check for slipped or broken downpipes,
and climbing plants such as ivy should be
controlled as they can act as sails in high
winds, pulling off anything they are attached to.
Over-chutes should be incorporated in any new
work wherever there is a risk of ponding from
a blocked downpipe (see photo, middle right,
for example), and in areas of high snowfall,
trace heating should be introduced to maintain
ice-free pathways for drainage, particularly
through valley gutters and behind parapets.
CLIMATE CHANGE
According to the Met Office, rainfall patterns
are changing across the globe, and in the
UK recently, rainfall has been decreasing