Any attempt to design flood protection into a house has to start with an assessment of the risk, i.e. the probable flood depth that the house will be subjected to. Houses likely to flood to a significant depth (500mm or more) should not attempt to keep water out, as this could cause the house to collapse due to hydrostatic pressure. Instead, you have to design with resilient materials so that the damage is limited and the house is able to dry out afterwards.

For shallow-flood homes, it makes sense to incorporate flood defences to keep the water at bay. There are a variety of flood-barrier products on the market (check out www.floodprotection.co.uk), which may perform well over a short period but do require some intervention by the householder. If you are out, the barriers won’t put themselves in place, so it’s not a good idea to rely on them solely, designing also with resilient materials. But what do we mean by resilient materials?

Foundations

Solid ground-bearing concrete slabs are the preferred option. Suspended floors may present problems as the subfloor space will need cleaning out after a flood. If you have to use a suspended floor, pay attention to the air bricks required for ventilation purposes: you can get products for capping these. Also consider incorporating a post-flood drain-off point.

Timber

Timber doesn’t withstand prolonged immersion in water and plywoods, MDF and OSB like it even less. So it’s a good idea to avoid timber framed walls and products like SIPs (structural insulated panels).

Cement and lime renders are preferable to gypsum plasterboard. If you do fit plasterboard, fit it landscape rather than portrait, so the bottom layer can be easily replaced.

Insulation

Mineral wool and natural wool insulation don’t like being immersed in water. Closedcell, plastic insulations, such as expanded polystyrene and polyurethane, are pretty much water-resistant and are preferable. Extruded polystyrene is particularly good. You can learn about the options available in our guide to the different types of insulation.

Bricks

Handmade bricks are very absorbent but engineering bricks are virtually waterproof, so use them up to likely flood levels.

Doors

Generally PVCu external doors are better than timber. Hollow-core timber doors, in particular, should be avoided. Patio and folding doorsets are best left out. Specify doors with good locking/sealing mechanisms. If possible, raise the thresholds (one must have a level threshold for wheelchair access).

Fixtures and Fittings

Kitchens: Avoid fittings made with materials like MDF. Plastic or stainless steel are ideal; natural wood finishes will be preferable to manufactured wood products.

Place sockets and appliances as high as possible. Built-in ovens must be at eye level.

One nasty aspect of flooding is sewers and drains ‘surcharge’, causing their contents to back up into affected homes. However, drain manufacturers now produce one-way flap valves which will prevent backflow.

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  • Anonymous

    YOU HAVE NOT MENTIONED IN YOUR PIECE THAT YOU ARE PROBABLY
    UNLIKELY TO GET INSURANCE IF YOUR ARE BUILDING IN A FLOOD ZONE.

  • Jason Orme

    Unlikely, or just more expensive? We’d be interested to get readers’ genuine experiences of the cost of insuring a newly built home in a flood-risk area.

  • john hillan

    Jason; re "Unlikely, or just more expensive etc " ….would also be interested to hear the responses but, in truth, surely it is reasonable to expect past experiences of pricing for flood risk area homes to become "somewhat irrelevant" after the experiences of the past couple of years and especially after this winter and particularly for homes in those areas which have flooded. House insurance is not compulsory (unlike vehicle insurance) and I suspect that commercial enterprises (which do include nearly all insurance companies) will not run "unnecessarily high" risks. I suspect that they will simply exclude "flood risks" from house insurance policies or will price premiums so high as to be effectively unaffordable (as are car insurance premiums for many young drivers) and those that do continue to include the risk at affordable rates will either be taking unnecessarily high risks (not attractive to most businesses, and especially not for public quoted businesses with shareholders) or expecting cross subsidies from (what are likely to be unnecessarily high) premiums from their non flood risk homes. In turn these latter premiums will be undercut by other insurers who do not run the same risks and so in time that cross subsidy will disappear as non flood risk homeowners find cheaper premiums with insurers who have eliminated the flood risk homes from their portfolios. In truth the issue of future flood risk insurance cover and the price of premiums is potentially as unpleasant for flooded areas, and indeed for potential flood risk areas, as is likely to be the future valuation and saleability of those homes. The future will, as ever, provide the answers. In the meantime, all such owners have my sympathy for what they are presently going through, as well as for dealing with such issues in the future.

  • Veronica Brophy

    In June of 2013, the Association of British Insurers (ABI) reached a Memorandum of Understanding with the Government regarding flood insurance cover. This was an extension of a previous agreement. The Memorandum proposes imposing a levy on all insurance policies to ensure affordable cover remains available to those who are at higher flood risk, although the ABI maintain that this levy doesn

  • Anonymous

    House construction in flood-prone areas has been done since the advent of building. It is well executed and totally accepted in many countries. There, local regulations include controls to ensure the techniques and materials are suitable. In many areas you see simple, raised mounds, with no void, bringing the ground floor clear of the 100 year flood level.
    Services, including drainage are designed and provided with respect to the zone regulations. All aspects are enforced by knowledgeable officials. The land prices reflect the additional construction costs.
    What’s so difficult? It should all be in the local regulations.

  • john hillan

    Veronica’s comment and the abi website details re the MoU/Flood Re scheme are certainly very interesting and potentially comforting to households (or rather that should be to "existing insured households" who stay with their insurer or to homes built before 1 January 2009 since newer homes will be excluded to avoid incentivising unwise building in flood risk areas).

    I read that the agreement is due to raise (initially) £180M annually and is to be implemented in summer 2015. I wonder if winter 2014 might prove to be a ‘game changer’. With the basis of the proposals being an annual levy equal to a fund of £180M (at the outset) and given the 2012 flooding affected more than 8,000 properties and caused £400 million worth of damage, the present situation will ensure the fund is, from the outset (pardon the pun) ‘under water’.

    It is also clear that the Flood Re scheme was designed "to fully cover at least 99.5% of years…. to cover losses up to those expected in a 1 in 200 year – a year six times worse than 2007" but in the light of the present circumstances, maybe that it looking at the situation rather optimistically! Certainly not an encouraging start

    Interesting to see that the Flood Re scheme was not designed to cover

  • john hillan

    P.S. maybe I should also have added as per ABI website:
    https://www.abi.org.uk/Insurance-and-savings/Topics-and-issues/~/~/~/link.aspx?_id=E483D07DA3BD43BDB730A671A1C853CA&_z=z

    Pre introduction of the Flood Re scheme …..in the meantime whilst ABI members will voluntarily continue to meet their commitments to their existing customers under the old Statement of Principles agreement this only means they will continue to offer cover to existing customers where flood risk is not

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