Flood risk assessment when buying a house

The Environment Agency estimates that at least one in six properties is currently at serious risk of flooding from rivers, the sea and other sources. That figure is predicted to double to one in three by 2050.

For buyers, understanding both the flood risk and flood history of a property and its surroundings is an important part of due diligence before exchange.

To put the risk into context, the most common causes of flooding are:

River flooding: when rainfall saturates the ground and drains into rivers, water levels rise until banks are breached, flooding the surrounding area.

Surface water flooding: when drainage systems are overwhelmed by rainfall, water accumulates on the surface rather than draining away.

Sewer flooding: when the sewerage system is overwhelmed or blocked, water escapes and floods the surrounding area.

Groundwater flooding: when heavy rainfall raises the water table until it emerges above ground level.

Coastal flooding: a particular risk for low-lying coastal properties, caused by a combination of high tides and storm conditions. Salt water is especially damaging as sodium is chemically reactive and corrosive, penetrating building materials and causing long-term problems.

The impact of flooding on a home goes beyond the immediate structural damage. Floors may need to be completely replaced, walls replastered, electrics tested and replaced and other services repaired. The building will need to be thoroughly dried out before remedial work can begin, which can take weeks.

Personal belongings, furniture and fittings may be lost entirely. And the disruption of living elsewhere while repairs are carried out should not be underestimated.

Flood damage costs UK households and businesses around £2.2 billion per year, according to government figures. For homes that have previously flooded, that history will affect both insurance costs and saleability.

Before committing to a purchase in a flood-prone area, these are the key questions to establish:

• Is the property located in a flood zone or area at risk of flooding?
• Has the property previously been affected by flooding?
• Where flooding is known, what was its source: river, coastal, surface water or drainage?
• What repair works have been carried out and when?
• What flood prevention works have been completed since the last flood?
• Is suitable flood insurance available at a reasonable premium?
• Are there higher-than-normal premiums or high excesses imposed by insurers?

The Environment Agency produces flood risk maps, including flood zone designations, which are a good starting point for assessing the risk at a specific address.

Obtaining insurance against flood risk at a reasonable premium is important to the viability of any purchase. Insurers assess the general flood risk for a property and the surrounding areas, which means a home may be considered high risk even without a history of flooding.

If flood insurance premiums are very high or cover cannot be obtained, this will affect the property's value and saleability. For purchases with a mortgage, lenders require buildings insurance as a condition of lending. Without adequate flood cover, securing a mortgage may be difficult.

The government's Flood Re scheme was set up to help. All homeowners pay a levy on their insurance premiums, which subsidises flood cover for properties that would otherwise be uninsurable. It is worth checking whether a property you are considering is eligible.

Always check the details of any insurance policy carefully and confirm that flood damage is explicitly included in the cover.

As part of a RICS Level 2 HomeBuyer Report or RICS Level 3 building survey, 

the surveyor will look for any evidence of previous flooding or water ingress in the property, assess the condition of the structure with this in mind and note anything that warrants further investigation.

Where there are concerns, the surveyor may recommend a specialist flood risk assessment, which provides a detailed analysis of the flood history of the property and its area, the likelihood of future flooding and advice on flood prevention measures.

Your conveyancing solicitor's searches will also include environmental data that covers flood risk, giving you a fuller picture alongside the survey findings. You can find out more about what each survey level costs on our survey cost page.

At Surveyor Local, we work exclusively with RICS-accredited chartered surveyors across England and Wales. Our team can arrange a survey quickly and at a competitive price.

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