Flooding and old buildings

Incredibly, a YouGov survey commissioned by Landmark Information Group has revealed that, although one in four homes are at risk of flooding, 83% of homeowners don’t believe their homes are at risk.

In the hope of making people more aware, Landmark – a supplier of digital mapping services, property and environmental risk information – launched National Flood Risk Awareness Week in conjunction with the National Flood Forum. In its wake it seemed useful to highlight some of the things to think about if floodwater does enter a building, especially an old one.

Speed but not haste is the key. Always aim to keep as much original fabric as possible and clean and repair sensitively to avoid further damage and loss. Remember that the approach promoted by some insurance companies can be highly damaging to old buildings so seek advice from the local planning authority’s conservation officer or other experts. The English Heritage publication Flooding and Historic Buildings is invaluable.

Once the building is safe to enter, clear away the water, mud and silt from inside, under floors and from the bottom of external walls. Encourage ventilation by clearing air-bricks of silt, moving furniture and pictures away from walls and lifting carpets and other floor coverings. With suspended floors, lift a number of floorboards (but no more than necessary) in each room to allow air to circulate, taking extra care when lifting swollen floorboards to avoid damage. If items such as panelling, door frames and skirting boards have to be dismantled, the work should be done with great care and by a good carpenter. Remember to number and record the position of items as they’re removed and turn them regularly to limit warping.

Don’t discard items until you are absolutely sure they can’t be conserved. They may in any case serve as a useful model to create replicas or when trying to find matches. Where appropriate get advice from a conservator or conservation architect.

Care and patience is needed when drying out old buildings. Bringing in heaters or turning the central heating to full can be catastrophic, making the remedial work more damaging than the flood itself. The work must be done gently and slowly through ventilation and with the aid of dehumidifiers. Fans speed up the drying process by increasing airflow and the evaporation rate.

Windows and doors, including cupboard doors, should be left open but be aware of the security risk and, if necessary, fit temporary grilles to secure openings. Stripping non-historic wall coverings will also help the drying process. Older lime based plasters usually soften when wet but generally harden again when dry. More modern plasters tend to deteriorate and may need to be replaced.

Don’t attempt to redecorate until the fabric has totally dried out. When you do, it’s more important than ever to use traditional ‘breathable’ paints rather than modern, potentially impermeable finishes.

Image credit: Landmark Information Group