Making it resilient
There are a range of options for making properties more flood resilient. These include traditional drainage, Sustainable Drainage Systems (SuDS) which are approaches to manage rainfall and surface water and Property Flood Resilience (PFR). The focus of this website is on PFR.
Numerous factors influence the flood resilience of a property. These relate to the specific flood hazards and risk as well as considerations for the property. This should be explored as part of the process of delivering PFR, but this context will include:
Property Flood Resilience (PFR) is an important part of managing flood risk. It includes measures that improve flood resilience at the building scale, helping to reduce the damage and disruption caused by flooding. There are different PFR approaches and measures which can either provide flood “resistance” or flood “recoverability”.
Flood Re has developed a PFR immersive experience here to show how a house can be modified to be more resilient.
Making it resilient
Flood resistance limits or reduces the amount of water entering a property and flood recoverability limits the damage and disruption caused when water enters a building. PFR helps manage the risks to people and property. It minimises flood damage and speeds up recovery and reoccupation following flooding. PFR measures can also buy extra time to fit further PFR measures, follow flood plans, get people, pets and valuables to safety, and can sometimes make obtaining insurance easier.
Elements of flood resistance and recoverability can be used for any property. The choice of PFR options depends on the risks faced, the characteristics of the property and personal preferences.
Alongside modifying or adapting properties, being prepared is an important part of flood resilience. This is about understanding your flood risk, signing up for flood warnings and having a flood plan. These help reduce the impact, disruption and damage caused by flooding – improving your overall resilience. Storing or moving valuable, personal items above the potential flooding level can spare you and others from anguish and frustration.
Flood resistance and recoverability measures can be combined, because resistance measures cannot remove all flood risks. Complete protection from flooding is very challenging. PFR measures have some limitations, whether these are physical, structural constraints or potentially related to human error.
PFR needs to be context specific, and approaches for removing floodwater from a building (e.g pumps and hoses) during, or following a flood also requires some planning.
The images above demonstrate what flood resilience measures can be achieved in and around a home, or business.
The PFR measures will need to be suitable for the type of flooding, the building and the occupant or end user. The Code of Practice for PFR sets out good practice for PFR delivery and provides guidance on how it should be planned and delivered. The process is generally broken into design, construction, and operation and maintenance of PFR. Further information can be found here.
The Code of Practice for PFR should be followed. It is also important that any PFR measures chosen should be tested and have a BSI Kitemark. Contractors (whether flood risk assessors, surveyors or building contractors) should have appropriate training and experience. Training is available from CIWEM and appropriate certification for PFR professionals is in development.
The age, listed status and location of the property, whether it is in a conservation area for example, can have implications for PFR. In some cases, older, more traditional properties are harder to modify with flood resilient measures, so will require different approaches. If a building is listed, specialist input will need to be obtained and approval from the local conservation officer at the Local Authority is required before making any changes. More information can be found in this guidance from Historic England.
Flood resistance measures keep as much water as possible out of a property. They limit the amount of water seeping through gaps and holes in walls, or through any openings on the ground level of a property. Openings including windows, doorways, and any pipe or service entry points on a wall or floor will need to be blocked and made watertight. Resistance measures can sometimes be referred to as a “water exclusion” approach, or strategy.
Flood resistance usually requires the installation of products (like door and window barriers) that can either be permanently in place, or temporarily, which requires manual fitting just before the flood.
Permanent resistance products, also sometimes referred to as “passive resistance measures”, are fitted, left in place and always ready to work (e.g. full height flood doors). Temporary measures, sometimes referred to as “active resistance measures”, are usually stored on site and then manually put in place when flooding is expected, and should be removed and cleaned (e.g. door, or window flood barriers).
If building occupiers, or end users are likely to be away for long periods of time, passive resistance measures may be more suitable. Likewise, it’s important to consider whether people can install the temporary PFR measures in terms of their weight and mobility.
A successful flood resistance, or water exclusion approach, requires every possible point of water entry to be identified and sealed. If a single point of entry is missed, or a flood resistance product fails the property may begin to flood.
A resistance approach is generally only recommended for floodwater depth of up to 60 cm. Providing flood resistance at greater heights may cause structural damage to some properties. Professional input from a structural engineer should be obtained before considering resistance measures higher than 60 cm.
Non-return valves
These can be fitted to pipes to ensure that water does not flow in and enter the building while allowing wastewater to flow to the sewer system. Non-return valves can also be fitted to the foul (wastewater) sewer, to stop sewage from backing up and flooding inside properties. If a non-return valve cannot be fitted, a bung (small inflatable ball) can be used to block the toilet.
Flood barriers
Flood doors and windows
Flood doors and windows create a water-resistant seal when closed. These come in a variety of designs, colours and finishes looking and generally operating the same as ordinary doors and windows. These are a passive PFR measure and do not require any manual fitting.
Flood gates
Self-closing airbricks
Automatic airbricks replace traditional air bricks and allow air to circulate and enter the building, but do not allow water to enter.
Air vent protection
If air vents are in use and cannot be raised above the flood level, protection measures can be used. This should be discussed and installed by a specialist contractor and approved by a gas safe engineer.
Cavity membrane/drainage system
These deal with flood water that enters a building. The drainage system collects the water around walls and/or floors, directs water into drainage channels or system and then pumps it out of the building.
Puddle pumps
Submersible or puddle sucker pumps can be portable and used to remove flood water through a discharge pipe reducing the damage caused.
Sump pumps
These remove water that has accumulated in a collection sump. Flood water is pumped through a discharge pipe to the outside of the building.
Tanking
Properties with a basement or ground floors prone to flooding can be tanked internally to reduce water entry through the walls and floor. This can be useful for groundwater flooding. However, consider the building fabric and method of construction before considering tanking.
Sealing of walls
Gaps and holes in external walls, particularly around wires and pipes need to be sealed either by water resistant mortar, or silicone. In some cases a waterproof, breathable spray may be suitable for application and can also be applied to external walls to reduce the risk of water soaking into the building. However, consider the building fabric and method of construction before considering sealing.
Re-pointing
This helps seal gaps and cracks in external walls that can allow water into the building.
Often during media coverage of flooding the use of sandbags is seen. However, sandbags are not suitable for flood resilience, as they can fail and leak, and many can also become heavily contaminated after flooding. Sandbags may help divert the flow of water, but there are other products that are easier to install and more effective.
If sandbags are used as a last resort, ensure they are stacked appropriately and a waterproof membrane is used. This YouTube video from the Gloucestershire Local Resilience Forum explains how it can be done.
Operation and maintenance of PFR measures are key parts of providing property flood resilience and is covered in the Code of Practice for PFR. Those responsible for using PFR should understand how PFR works and know where the PFR measures (and all the components and necessary tools) are stored as well as how they can be fitted. Operation and maintenance instructions should be provided by the manufacturer, and they should be part of a handover pack.
It is recommended that a drill, or test PFR installations are undertaken to ensure those that need to are familiar with where everything is located and know how it fits together before a real flood. There’s a chance that it will be dark and wet when flooding occurs and the PFR measures are needed most!
Most PFR resistance measures are designed to resist water entry to a particular standard. Regular inspections should be undertaken in line with the handover pack and manufacturer’s guidelines – these tend to suggest annual or biannual inspections. There will also be instructions for cleaning, decontaminating and maintaining PFR measures following use during a flood. Any testing, maintenance and changes to PFR measures should be recorded in the handover pack.
Manufacturer’s guidelines should be referred for specific maintenance requirements. Some general maintenance considerations are presented in the table below for an indication of requirements.
This approach accepts that water may enter a property, this is sometimes called a “water entry” approach. Recoverability measures reduce, or limit the damage caused by flood water. They enable the drying, clean-up and repair process to happen quickly, speeding up recovery and reoccupation. Flood recoverable measures were historically referred to as “flood resilient” measures. With the introduction of the Code of Practice for PFR, the term “flood resilient” has been replaced by “flood recoverability”, or “flood recoverable”.
Visiting and BRE’s Flood Resilient Repair House webpages helps put flood resistant and recoverable PFR measures in context.
Approaches like these combined with a flood plan where utensils, equipment, devices, fixtures, like sofas, tables etc can be moved, or raised above the potential flood levels can reduce damage and disruption, helping to speed up recovery and reoccupation.
It’s important that changes to implement flood recoverability in a property are clearly understood and recorded. This will also help ensure that materials designed to be flooded and recoverable are not removed by mistake following any subsequent flooding.
Replacing suspended timber floors with a solid concrete floor, or concrete based stone can reduce the chances of damage. Using ceramic tiles for floors and skirting boards instead of carpet or laminated flooring also reduces damage, with tiles often simply requiring cleaning rather than replacement.
Replacing floorboards and joists with water resistant, treated timber or vitrified wooden floor can reduce water absorption allowing the floor to dry out quicker. Installing a chemical damp-proof course below a suspended timber floor reduces sub-floor condensation and associated damage.
Flood recoverable materials and design approaches can be used for many rooms in a property. Appliances can be installed and used in a way that reduces the risk of flood damage. There are a variety of approaches to make a kitchen (and other rooms) more flood recoverable, and therefore resilient. These include:
Replacing suspended timber floors with a solid concrete floor, or concrete based stone can reduce the chances of damage. Using ceramic tiles for floors and skirting boards instead of carpet or laminated flooring also reduces damage, with tiles often simply requiring cleaning rather than replacement.
Replacing floorboards and joists with water resistant, treated timber or vitrified wooden floor can reduce water absorption allowing the floor to dry out quicker. Installing a chemical damp-proof course below a suspended timber floor reduces sub-floor condensation and associated damage.
Power supply and electrics for ground floor properties can often be separated from other floors on the building’s circuit board or wiring. This enables power on the ground floor to be isolated and turned off. Consumer units, and meters can be raised out of the potential flood depth. Electrical wiring can also be installed and wired from the ceiling down so wiring, sockets and outlets are raised above the potential flooding level. Electrical appliances and equipment like televisions can be wall mounted or raised.
Likewise, boilers, heat-pumps and other services like air conditioning units can be relocated to a place where flood risk is reduced. Services could be mounted on the wall above the flood level or re-installed on the first floor. This could reduce the chances of expensive damage during a flood event and enable them to be used after a flood to assist with recovery.
The use of water recoverable products, materials and paints on walls can reduce the impact of damage. Lime rendering may be used when plastering, as this does not trap moisture and degrade, it also allows the walls to breathe following a flood. Plasterboard can be replaced with magnesium oxide boards that don’t absorb water, or conventional gypsum boards can be installed horizontally, so the lowest sections are the only ones affected if flooding occurs and can be more easily replaced.
These case studies demonstrate what can be done to improve the flood resilience of properties by being better prepared and installing flood resistance and recoverability measures.
| Measure | Maintenance consideration |
| Flood barriers | Check seals and frames for grit, debris and anything that could compromise operation and/or water resistance. Check stanchions, supports and other fixings. |
| Flood doors and windows | Check seals, handles, hinges, glazing and panels. |
| Flood gates | Check alignment, seals, handles and hinges. |
| Self-closing airbricks | Check that no debris or silt has entered the airbrick. Check for anything that can obstruct the mechanism. |
| Air vent protection | Check seals. |
| Non-return valves | Check mechanisms, seals and sealing areas. Clean the mechanism if necessary. |
| Cavity membrane /drainage system | Should be inspected annually by a specialist company to check system is free from limescale, silt or other blockages. |
| Sump pumps | Inspected annually, often through a service contract. Check chamber, internal pipework/fittings, float switches and cables. Test pumps, clean, wash down mechanisms. Check power/backups, and alarms are working. |
| Tanking | Covered by a warranty – and can be difficult to inspect. However, cracks or factures should be checked. |
| Sealing of walls | Annual or bi-annual checking for weathering and cracks of sealant and waterproofing of walls. |
| Re-pointing | Annual or bi-annual inspection of external walls for potential weather, cracks and points of water entry. |
