Advice Sheet 4 Measures to Make Your Property More Resilient to Flood Damage

Circumstances can differ from one property to another. Any information or advice is for guidance and is given in good faith but without warranty. Whilst we have made every effort to ensure its accuracy and completeness neither the author nor the Carse of Gowrie Sustainability Group nor its office bearers can accept any liability arising from errors or omissions.

Advice sheet 4 Measures to make your property more resilient to flood damage

The Scottish Government has announced its commitment to sustainable flood management.[1]

“Sustainable flood management provides the maximum possible social and economic resilienceagainst flooding, by protecting and working with the environment, in a way which is fair and affordable both now and in the future.”

Resilience in turn is defined as: “the ability to recover quickly and easily”.

Housing stock turnover is low with existing stock making up 99% of all homes at any given year[2]. If this rate is sustained, the majority of the housing stock will continue to consist of existing buildings for many decades to come. The Sustainable Development Commission’s estimates for the UK’s 2050 housing stock suggest that around 70% has already been built[3]. Not only that, but architects are still not trained in taking climate change into account and in the whole world there is still only one text book on the subject.[4]

We are very fortunate in Scotland that building regulations for new build properties do require considerable resilience against flooding and the Scottish Building Research Establishment at East Kilbride is a world leader in this subject. Nevertheless for existing buildings it is largely left to the property owner to make decisions on retrofitting for resilience.

Resistance

But first look at resistance, how to keep the water out of your property. A very simple precaution is simply to keep watercourses and drainage gullies clean, and we are fortunate that in Scotland, unlike England, there are statutory duties on local authorities to do this and you can report any concerns to them.

If the problem is surface water, the answer may be a flood wall around your garden. This can be constructed of a double layer of engineering bricks, covered in a mound of earth to form a “berm”. For access, you can either have ramps or use a demountable flood defence system (see advice sheet 1). This is more difficult for semi detached or terraced properties unless you can persuade the neighbours to join in. Again we are fortunate in Scotland in that such local flood defences are allowed. They are not allowed in England. However you should make sure that in defending your property you are not simply passing the flood problem on to a neighbour.

For periods of heavy rainfall wide storm gutters should be provided, and kept clean. Walls, and especially their bases, should be protected from driving rain and splash back, for example by having gravel beds at the foot of walls and making sure that gardens slope away from the wall. Make sure that the wall has a damp proof course (dpc) at least 150mm above the ground with nothing to bridge the dpc.

Many floods are actually caused by backup in the drains, leading to water overflowing from ground floor baths or toilets. The ideal situation here is a one way flap valve fitted into the sewage system. A stopgap solution is a bladder from a football which can be partially inflated and pushed down the toilet, and held in place with a sandbag.

Resistance measures to flooding are about identifying and blocking all potential entry points. For short duration floods, entry points include doors, air bricks, sinks and toilets, and gaps in external walls around pipes and cables. For longer durations, measures will need to be taken to prevent water entering through the walls.

For shallow floods of less than 1 metre depth demountable defences may be the answer (see advice sheet 1).

In deep floods (over 1 m), you may have to resign yourself to letting the water in because a large imbalance between the water level inside and outside can lead to structural damage to your walls.

This is where resilience comes in.

Resilience

Resilience is about reducing the time and cost of cleaning up after a flood, and avoiding the need to replace appliances, floor and wall coverings etc.

It is all about adaptation and if you are in a flood hazard area resilience should be considered whenever you are carrying out maintenance or redecoration. In particular it should be considered when repairing flood damage.[5]

Here are some ideas:

Fitting rising hinges so doors can be removed, and laid flat to dry without warping.
Using water-resistant paint or ceramic tiles for floors or the lower portions of internal walls,
Raising electrical points above flood level with wiring drops from above
Relocating meters and the boiler above flood level
Replace carpets with vinyl and ceramic tiles and/or rugs.
Avoid using chipboard for floors or kitchen cabinets. Choose cabinets on legs. In extreme cases, such as Shrewsbury, families have abandoned the ground floor altogether and use it for car parking.

Some insurance companies and building contractors will put pressure on you to replace everything with new materials. This is not always ideal. For example if you have doors made of Victorian pitch pine, be aware that this will dry out very well after a flood if laid flat and allowed to dry slowly. A modern replacement of hollow mdf or chipboard may be quick but will disintegrate if you have another flood. It is virtually impossible to buy new doors made of pitch pine, and builders do very well from taking pitch pine doors from flooded houses, drying them out and selling them to architectural salvage merchants.

Resilient reinstatement

Insurance companies may resist “resilient reinstatement” on the grounds that it is what they call “betterment”. However if you insist, they may agree if you pay the difference in cost which may be quite small. This will stand you in good stead next time there is a flood, especially if you find yourself without insurance cover.

Flooding can result in massive amounts of building materials being sent to landfill and replaced with new high embedded energy materials. Where buildings are constructed in high flood risk areas they should not have any insulation or absorbent materials at all, because this increases the cost of repairs and drying out time and energy after a flood.

The rights of David Crichton to be identified as the author of this work have been asserted in accordance with the Copyright, Designs and Patents Act 1988.

[1] ‘Flood Risk Management (Scotland) Act 2009: Delivering Sustainable Flood Risk Management’ The Scottish Government, Edinburgh 23 June 2011

accessed 24.6.11.

[2]Your home in a changing climate. Retrofitting Existing Homes for Climate Change Impacts, Three Regions Climate Change Group (2008)

[3] StockTake: Delivering Improvements in Existing Housing, Sustainable Development Commission (2007) [online] commission.org.uk/publications/downloads/Stock_Take_UK_Housing.pdf

[4]Roaf, S. Crichton, D., and Nicol, F. , 2009. “Adapting Buildings and Cities for Climate Change.” (Second edition) 384pp. Architectural Press, Oxford. ISBN 978 1 85617 720 7.

[5] Crichton, D, 2007a What can cities do to increase resilience? Phil. Trans. R. Soc 10. 1098 pp1 – 11. Royal Society, London.