Flood risks
insulation, providing a watertight layer between the home and the next door property, and the other has, for the purpose of demonstration, been converted to a section of cavity wall, the cavity being filled with resilient injected foam insulation. All four walls have been finished internally with
moisture resisting magnesium oxide wall board, or with a waterproofing layer of natural cement render. The front and back doors have been replaced by new, flood resisting doors. These look just like normal doors, but have extra latches and bolts to hold them shut, resisting the pressure of water against them, and extra seals to keep that water outside.
Water solutions
Keeping water out with flood resisting doors still leaves another entry point at risk: the toilet pan. Once the sewers are overwhelmed by floodwater, a mix of foul waste and floodwater can enter a home via the underground drains. A simple double acting ‘flap valve’ in the main drain connection will keep this at bay. The home has a demonstration toilet fitted with such a valve to show how this works. These measures will help protect a home in
the event of a short term flash flood. However, there comes a point where the weight of water against the outside of a building during a period of prolonged flooding could lead to the risk of walls collapsing. A cubic metre of water weighs one tonne, and once a building is surrounded by water, the forces acting on the walls can become considerable. In the case of the BRE home, the doors are designed to hold water back up to a depth of about 600mm above the floor level, but after that it is safer, from a structural point of view, to let the water in.
Before that point is reached though, there should be time to move vulnerable items up above the potential flood level. To help with this, the kitchen units are designed with lift out baskets, and items such as the fridge are set at worktop level to be above the flood line. As well as the perimeter drain channels, a pair of gullies were installed in the new floor, also connected to the sump pump. In the demonstration home, these are in full view
in the centre of the room, but in a real home they could be placed out of sight, for example under the stairs or beneath kitchen units. These drains ensure that when the flood level does drop outside, water in the house can be quickly pumped away again. The waterproof kitchen units can be hosed
down and disinfected, and the tiled floors washed clean. If any damage occurs to the water resisting wall boards, because these are fitted horizontally the lower sections can be quickly removed and replaced, and the combination of waterproof insulation and the cavity drain barrier in the wall means very little time is needed before replacement boards can be fitted. Many of these measures cost no more than
the ‘standard’ post flood repairs. Others such as the pump installation do add costs, but the pay off for this is significant savings following any future flooding, and a reduction in the sums insurers have to cover in flood prone locations. The BRE home had an initial ‘thorough soaking’ when filmed for BBC Countryfile in February, shortly before its official opening by Emma Howard Boyd, chair of the Environment Agency, and Clare Moriarty, Permanent Secretary at Defra. There are plans to subject the building to a
more complete flooding test in the near future, the home being a partnership project featuring Defra, AXA Insurance, the British Damage Management Association, the BRE Centre for Resilience, the BRE Trust, Cunningham Lindsay, Natural Cement, and the Property Care Association
Peter White is communications manager at BRE. For more information, view page 5
A full listing of the project partners, along with a slideshow setting out all the stages of the repair work, can be seen at
www.bre.
co.uk/floodhouse Parts of this content appear on the same
BRE webpage, written by Peter White and placed online to coincide with the broadcast of BBC Countryfile’s Flooding Special in February 2017. The Property Flood Resilience Action Plan can be downloaded free of charge from the Defra website – search online for ‘Bonfield Flood Plan’.
www.frmjournal.com DECEMBER 2017/JANUARY 2018 23
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