Flood Risk Advice
Historic England has prepared advice and guidance to help you with measures you can take to prevent flood water entering your property. It also covers changes you can make to your home to minimise damage if floodwater does get in. Although most historic buildings are very durable and relatively resistant to flooding, they can still suffer substantial damage.
Being prepared for flooding
If your home is at risk there are some basic checks that need to be made:
- Carry out basic building maintenance to minimise potential damage
- Are building drainage systems working efficiently?
- Check any adjacent land drainage such as ditches and water courses for blockages, particularly after heavy rainfall
- Check external ground levels are not too high adjacent to the building. These should be at least 150mm below internal floor level and damp proof course level
- Prepare an emergency home/family flood plan and flood kit
- Check your insurance cover for any special provisions for historic buildings
Consider flood resistance measures to keep water out
Flood protection measures can reduce flood damage by as much as 50 – 80% by limiting the amount of water entering your home.
Consider having a flood risk and property protection survey from an architect / surveyor or engineer who has experience with historic buildings and flooding damage. Try to understand how the property is constructed and what is significant and vulnerable to flooding. What measures would be most appropriate? Could flood protection measures be positioned away from the property?
You may need to consider what statutory consents are required for any permanent measures, particularly if your home is listed or in a conservation area. The following protection measures might be considered:
- Adding coverings, such as door guards and air brick covers to any openings. These may only keep water out for a limited period, depending on the level of flood water, but they will give you time to move valuable possessions to safety and restrict the entry of debris. A range of certificated (BSI) products are available. Water causing flooding to a depth greater than 1m should not be held back because of the risk of structural damage
- Using temporary flood barriers consisting of interlocking units kept in place by the weight of flood water can be useful, but will require storage
- Remove extensive hard surfaces around a building as this increases run-off and restricts water absorption by the ground
Products which aim to provide an impermeable barrier to the external wall of the property, such as coatings or tanking are best avoided as such systems can trap damp within the structure of the building. This will prevent the fabric from drying naturally.
Minimising damage if flooding is a possibility
There are many quite simple measures that you can take to minimise damage if flood water does enter your home.
- Installing or moving electrical circuitry above potential flood level
- Raising any vulnerable electrical equipment such as freezers above potential flood level
- Adding backflow valves to plumbing
- Adding a built in pump for cellar areas or sub-floors that are particularly vulnerable to flooding
- Ensuring that a few floorboards can be lifted when flood water subsides. This will assist drying and allow water to be pumped out of the sub-floor void
- Retaining lime plaster as this is porous and will dry out with the main wall. Modern gypsum plaster is slightly soluble and will become detached
- Avoiding composite wood materials such as chipboard and fibreboard for fixtures such as kitchen units as they will be ruined. Historic solid doors will be much more water resistant than modern hollow doors
Minimising damage after flooding
Repairs need to be considered in relation to how the building is constructed and the materials used. One solution does not fit all.
Older buildings behave differently to modern ones and as a consequence need much more careful attention after flooding. They are often built with more permeable materials like timber, lime mortars and plasters and soft bricks which will absorb water and need to be able to dry slowly.
Properties that are insured will be inspected by the insurer’s loss adjuster who may, depending on the extent of damage, bring in a surveyor to establish and specify the extent of repair works required. A recovery contractor appointed by the insurers would then be brought in to carry out repair works.
Historic buildings can be particularly vulnerable at this stage as inappropriate and potentially damaging works may be specified involving extensive removal of historic material. The appointed contractor may also have little or no experience with working on historic buildings.
Consider the following:
- Make a comprehensive photographic/video record of the damage
- Inform your insurance company that you need a loss adjuster/recovery contractor with experience of historic buildings to prevent unnecessary damage
- Obtain advice from the local planning authority’s conservation officer
- Establish whether any consent is required before any stripping out work or repairs are put in hand
- Obtain independent advice from an architect or surveyor who has experience with older buildings and who knows local contractors suited to this type of work
- Beware of bogus contractors who can take advantage of flood victims.