FOCUS
Flood risks
used in the BRE demonstration house, include: • water resistant insulation in the walls and under the floor (such as spray applied PUR foam or injected foamed cavity insulation)
•
kitchen units and doors made from resin bonded board, and fitted with all ceramic worktops
• waterproof magnesium oxide wall boards instead of gypsum plasterboard, or, if plasterboard is used, this should be fitted horizontally so that in future only the lower boards need replacement if damaged
• ceramic tiled floor and loose rugs in place of fitted carpets
As well as these measures, other things have been done to keep vulnerable items out of the way of any future flood water, as follows: • sockets and switches placed higher up the wall, and the wiring to them all coming from the ceiling
• •
appliances in the kitchen (fridge, oven, washing machine etc) mounted at worktop height
the lower kitchen cupboards fitted with slide out baskets so that they can be taken out and placed on the worktop if flooding is imminent
To prevent flooding entering the property from under the floor (which happens as groundwater rises, even if floodwater does not reach the door), these measures were taken: • membranes installed under the floor and in the walls* to divert water towards…
•
drain channels beneath the floor around the perimeter of the room, directing water into…
• a sump in the corner of the home fitted with automatic pumps to remove the water, pumping it outside, before it can reach up to the floor
(*The membrane in the wall means that if the adjoining property floods, water that seeps through the wall from next door is channelled away to prevent damage on your side. This allows repairs to start even if the neighbouring property is still affected.) And finally, to stem the flow of any flooding that
reaches above the door sill level, these were provided: • enhanced seals and locks to the doors and windows to make them floodproof air brick covers
•
• one way valves in the main drains to prevent water coming up into the home via the sewers
•
drains fitted flush with the floor, connected directly to the sump and pump (and so independent from the ‘mains drainage’), which can rapidly clear any flooding that does get into the home, pumping it out above the external floodwater level
Construction work
Prior to work starting, the unit was in a similar condition to that of a home that had suffered
serious flooding. Although not actually wet, plaster had been stripped from the walls to reveal brickwork, the damaged concrete floor screed had been removed to leave the solid subfloor, and the electrical installations had been taken out. The builder’s first job was to dig out a small pit in one corner of the home, to house the ‘sump pump’ – the sort of unit often found in basements. A network of shallow drainage channels was formed at the base of the inner walls and connected to the pump chamber, and a dimpled ‘drainage barrier’ membrane was laid across the floor. These measures mean any water that
percolates up into the building will now flow to the drain channels and will be pumped away without causing any damage in the event of rising groundwater levels. A layer of resilient insulation was placed over the membrane (since the floor was being replaced, it made sense to include sub floor insulation while the work was being done), and a flowing screed poured over to create a new, waterproof floor. This new floor was finished with ‘wood effect’ ceramic tiles, giving the appearance of timber floorboards but with a fully waterproof finish. A similar ‘cavity drainage membrane’ was fitted
to the wall separating the house from the home next door, as well as to the inner surface of one of the solid external walls. These also drain into the channels at the base of the walls and away to the pump. By adding this membrane to the dividing wall, even if the house next door remains saturated following a flood, the walls of the resilient home can quickly dry out once flood waters recede. These walls were insulated using resilient insulation board. Of the remaining two walls, one was insulated using a spray applied PUR foam
22 DECEMBER 2017/JANUARY 2018
www.frmjournal.com
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