The flood risk is increasing – but there are fears that damage to old buildings
is being compounded by unsuitable responses promoted by many insurance companies,
loss adjusters and contractors. Proceed with caution, says SPAB Technical Secretary
Douglas Kent
Q. Can I really do a great deal to avoid flood damage?
A. The causes of flooding in buildings range from pipe bursts, overflowing appliances
and fire-fighting to intense rainfall, poor site drainage, river surges and storm
tides. Though prevention is outside the direct control of property owners in many
cases, measures can usually be taken to reduce damage during flooding and the
subsequent cleaning, drying out and repair of a building.
Old buildings commonly suffer more harm from inappropriate remedial work following
flooding than from the event itself. Care should be taken to seek listed building
consent where necessary and engage specialists qualified to deal with old buildings.
The SPAB may be able to advise on suitable contacts.
Q. What precautions might I take against flooding?
A. Where no permanent barriers exist, temporary measures can be taken to delay floodwater
from entering a building. These include fitting removable door and window boards,
snap-on vent covers or wrap-round skirts, using sandbags, and applying sealant
to gaps and holes. Maintaining the condition of external render and pointing is
also wise. Steps can be taken, too, to combat the effects of floodwater once it
enters a building, such as providing improved access and drainage to underfloor
spaces, fitting anti-flood devices to foul drains and repositioning electrical
installations higher up.
It is generally advisable to avoid tanking, water-repellent solutions, modern
gypsum plaster and fitted carpets. Sensible flood precautions may sometimes help
you obtain insurance cover in high risk areas.
Q. How is a flood-damaged building best cleaned?
A. Act swiftly, rather than hastily, and never remove wet plaster, joinery or other
building components indiscriminately. Firstly, make sure the building is safe
(ie services turned off pending inspection and no obvious structural damage),
and fully photograph and record damage for later insurance claims. Then, after
letting the floodwater recede by itself, remove any remaining standing water and
drain voids (underfloor spaces, electrical ducts etc).
Mud, silt and debris should be shovelled up and appropriately disposed of, and
air bricks cleared. Surfaces should be completely rinsed down with detergents
and, where required, disinfected. Wear suitable protective clothing and beware
of hazardous materials that need to be dealt with by the authorities. Enzyme bioremediation
can be effective for removing oil contamination non-invasively.
Q. How should an old building be dried out after flooding?
A. To prevent serious damage, dry the building slowly, first by natural ventilation,
and then, where required, with extract fans, background heating and/or, unless
wallpaintings exist, dehumidifiers.
Keep opened doors and windows secure against intruders, perhaps using temporary
perforated boarding or metal grilles. Selected floorboards might need lifting
carefully to prevent buckling, and wall panelling and door and window linings
dismantled to hasten the drying of awkward spaces if specialist non-invasive techniques
are not employed. Protect very soft external brick or stone from frost with water-resistant
insulation and ventilated shelter. Drying may take several months and should be
continued until: moisture levels are at or lower than before flooding (ascertained
by assessing unaffected adjacent areas or properties); remaining moisture will
not support active timber decay; and building materials can finish returning to
equilibrium by themselves without further damage.
Q. What repairs may flooding necessitate for my old building?
A. Structural work is rarely required, a notable exception being with heavily-saturated
earth-based construction. Lime plaster tends to dry out on walls intact, whereas
daub, gypsum plaster and plasterboard are more vulnerable to water damage. Floorboards
and joinery items that are dried gently also usually survive flooding well, unlike
fibreboard, some insulation and certain other non-original materials. Electrical
installations frequently need renewing but if retained should be inspected regularly
in the aftermath of flooding. Also check the building periodically for signs of
structural movement and timber decay.
Salt deposits (‘efflorescence’) may appear during drying and can be brushed or
vacuumed off, although heavily salt-laden joints in stone or brick floors might
need repointing in lime.
Further Reading
Standard for the Repair of Buildings Following Flooding, CIRIA publication C623, by S Garvin, J Reid and M Scott, CIRIA, 2005
Flooding and Historic Buildings, English Heritage Technical Advice Note, 2004
