Flood - protect or prepare

I think we all know by now that flooding is a real issue. There are all sorts of statistics bandied about, such as 5,000,000 properties being at risk of flooding and 1 in 7 businesses having been harmed by flooding, but the reality is that it happens and it hurts. The changing climate means that more deluges are on their way, so that some previously dry properties will become wet in the future. Thankfully, it is now safe to buy a house: there are great reports available that highlight any risks and say what can be done about them.

But what can be done? Knowing about the problem is one thing, but it is solving it that really matters, especially if you already live in a house under threat. The good news is that there are ways to live with flooding.

Knowing like Noah

When you know the waters are likely to rise, you can protect your home and keep it dry. This is often called flood resistance and works by making your house waterproof, very much like a boat. Most buildings are full of far more holes than just the windows and doors, all of which have to be sealed if you want to stay dry. It can be fairly obvious to deal with the water you can see, but with most floods of any duration, the ground becomes saturated and water rises vertically up through the foundations.

The walls are all fairly easy to make water tight, such as fitting waterproof covers to doors and air-bricks. Costs usually range from about £2,000 for providing covers to air bricks, doors and windows, as well as fitting non-return valves to foul pipes and making sure the bricks are well pointed. These are the basics and can be enough for short floods from rainfall or rivers. Longer floods or rising groundwater will also need the floor to be made water tight, which is often highly disruptive and can cost well over £10,000.

These resistance measures will only work for comparatively short periods – days to weeks – as water will eventually get in. A ‘sump and pump’ arrangement will help to get rid of such water from a low-point in the foundations, but remember that a fair amount of cleaning and drying will be needed after every flood event. There is usually significant damage to gardens, garages and outbuildings.

Keeping the waters out will only be feasible for floods of less than about one metre deep, as beyond this the water becomes so heavy that is crushes the walls and can collapse the entire building. Worth avoiding! In deep floods, or when costs are prohibitive, the only sensible option is to adopt resilience measures.

Cleverer than Canute

Resilience works by allowing the water into your house, but being prepared for it. It is impossible to avoid some disruption whilst your house is full of water, but with careful preparation it need not be catastrophic. There is a pub in York that floods almost every year and has got its resilience measures down to such an art that they open the day after the waters recede.

Resilience works by changing the fabric of a building to make it safe during the flood, then easy to clean and dry afterwards. Common changes include moving wiring and power points higher up the walls, replacing normal plaster with waterproof varieties and taking all wood away from the flood zone (including doors and floor boards). The latter can be replaced by alternatives that do not absorb water, such as plastic or glass. It is also worth fitting non-return valves to the foul water pipes, since you do not want any return visits from the sewer!

Most flood waters are extremely dirty and leave behind a drift of mud and muck. It is therefore important to be able to sweep out and hose down the flooded areas, so nooks and crannies should be avoided. A sump and drain to wash the dirty water away will also be useful.

The cost of refitting a house with resilience measures will vary massively, depending on what needs changing. However, costs are unlikely to be less than £5,000 to do the job properly.

One size fits one

The solution to your flood problem will depend on many factors, from the type of flooding expected to the construction of your building. It is worth carrying out detailed research and probably consulting an expert, since making you home resistant or resilient is not generally a DIY undertaking. Experts will have to carry out much of the work, so it is worth talking to them to begin with.

The first step is to understand your flood risk – its type, depth and frequency – then design the most effective measures to deal with it. Landmark Information Group can help you take the next steps for your property, but there is also a lot of detailed generic information and case studies at www.knowyourfloodrisk.co.uk

Flooding is becoming a major concern of insurers and lenders, as well as affecting the value and saleability of your house in the future. The cost of action may be daunting, but is it nothing to the financial and emotional cost of not taking action. 

Author: Angus Middleton, Consultant, Argyll Environmental.