Adaptation Measures

Overview

Resistance or recoverability measures may not be enough to prevent the damaging effects of flooding. In such cases, adaptation will be necessary to prevent the total or partial loss of a building or asset.

Adaptation offers alternative options and approaches to allow for the continued use of a building. Measures will vary depending on the building's construction type and setting as well as which parts of the building are liable to flood. Any proposed adaptation work needs to factor in the environmental context of the building. Adaptation might not mean changing the building or structure, but altering the landscape around it.

Where adaptation is the only option, ensuring all stakeholders are on board at an early stage will facilitate a smooth planning and construction process. Consulting stakeholders may also bring about creative solutions that a single person or profession may not consider.

Adaptation has occurred throughout history, from installing electrical and heating systems to totally changing the use of a heritage building. There are even examples in the past of historic buildings being lifted and moved away from their original setting. This is not to suggest that adaptation decisions should be made lightly; rather, the impact on the building and its surrounding context needs to be thoroughly considered. There are more recent examples where buildings at risk of flooding have been adapted such as adding extensions to allow for loss of usable spaces, as discussed in Historic England's Webinar on Adapting to Flooding.

Adaptation requires careful consideration and management. The cost of the work and its compatibility with the original construction should be assessed, along with the impact on the building's significance and how it is used.

One approach is to adopt a multi-criteria assessment, as in the PFR Outliers project undertaken by Historic England in 2022. This suggests 14 different adaptations for one particular building. To develop this approach further, Historic England will be using the same methodology to assess adaptation to coastal erosion.

Where a historic building is at risk of frequent flooding, doing nothing will be significantly more damaging to the heritage asset then undertaking adaptation, resistance or recoverability measures. This is because doing nothing could result in there being no future viable use for the building.

Some adaptation measures are considered below, but the list is not exhaustive. Options should be assessed on a case-by-case basis, after understanding the structural detail and significance of the building.

Floors

Changing the floor material

Where flooding does not occur any higher than the floor and base of the wall, installing a more resilient floor material that dries quickly and can be cleaned easily, such as stone or tiles, is an appropriate adaptation. Installing a sump and pump system under a timber suspended floor is another option.

Raising the existing floor height

Raising the existing floor height above the floodwater level may be an option. For example, this may be possible where the ceiling is high, such as in a Georgian building or commercial space.

Raising the floor is usually only appropriate where the floodwater level is no more than 300mm above the existing floor finish. With consent, the floor can be raised by removing the old one and laying a new one, or by laying a new floor on top of the old. The latter option has been common practice in older buildings, where concrete flooring has been laid over quarry tiles. However, this often-irreversible adaptation damages the original floor. Careful design, specification and installation of a new raised floor can avoid such damage and preserve the existing materials.

Walls

Ensuring wall materials can manage the passage of water and vapour is the first step to enabling a building to recover quickly after a flood event.

Masonry walls generally don't require wholesale adaptation to flooding, unless they are at risk of frequent and intense flooding which would result in the building having no use.

It may be possible to adapt a timber-framed building by removing the lowest infill panels only and replacing them with a material that prevents the passage of liquid moisture. Alternatively, a timber-framed building could be lifted entirely to install a higher masonry plinth below, so that the timber which is most at risk of decay is protected.

Other options for adapting walls fall under major adaptation of the whole building, such as lifting it above the level of floodwater or relocating it.

Any work to adapt a building or understand its potential to fail from flooding will require a structural survey.

Windows and doors

Adapting windows and doors by raising their position above the flood line may provide a degree of resilience against flooding. However, changing their levels will impact a building's appearance and may complicate access for occupants.

Such changes may still be acceptable if the harm is outweighed by the increased resilience of the building. Where possible, reuse of the existing element or introducing one of the same design should be a consideration.

Additionally, alterations such as installing flood resistant secondary glazing windows or doors may be an option. Similar adaptations have been made to accommodate fire compartmentation in historic buildings.

Whole building adaptation

Lifting a building

In some cases, lifting a building above the flood zone may be possible. Although initially costly, lifting a building will provide long-term benefit and may be less expensive than repeated clean-ups and repairs after flood events.

Changing the ground floor to be non-habitable

A similar but more expensive approach to lifting the whole building would be to add on another storey or to insert a flood-resistant storey below. The ground floor would generally then need to become a non-habitable space.

All proposed alterations would need to be discussed with the local authority. Where a building experiences flooding on a regular basis, to a height of 300mm or more, adding a non-habitable storey will limit the chance of decay and deterioration to the building and inconvenience to its occupants.

For buildings that are not dwellings, it is likely to be more beneficial to make the ground floor area easy to clean and to keep surrounding units and machinery at higher levels, rather than adding a storey or lifting the building.