Flood Resistance and Resilience Measures for Planning
If your site carries some flood risk, a planning officer or the Environment Agency may ask you to design in flood resistance and resilience measures. These are the practical, physical measures built into a development to either keep floodwater out or limit the damage and speed up recovery if it does get in. Get them right and they can be the difference between a refusal and a consent, and between a building that's wrecked by a flood and one that's mopped out and back in use within days. This page explains what these measures are, how they differ, and how they fit into a flood risk assessment.
Resistance vs resilience: two different jobs
The terms get used interchangeably, but they describe two distinct strategies, and a good design often uses both.
**Resistance** is about keeping water out. The aim is to stop floodwater entering the building in the first place, or at least to hold it out for long enough that a short-duration flood passes without getting inside. This is sometimes called "dry-proofing".
**Resilience** (also called recoverability) accepts that water might get in, and focuses on limiting the damage and making the property quick and cheap to clean, dry and reoccupy. This is sometimes called "wet-proofing". It's the sensible approach where flood depths are likely to be high or where water could enter through the ground or services regardless of barriers.
The right balance depends on the depth, speed and duration of flooding at your site, which is something the flood risk assessment should establish before any measures are specified.
Flood resistance measures (keeping water out)
Resistance measures form a physical barrier between floodwater and the inside of the building. Common examples include:
- **Flood doors and demountable barriers** fitted across doorways and other openings.
- **Self-closing airbrick covers**, which seal automatically when water rises.
- **Non-return valves** on drains and sewer connections, to stop water and sewage backing up into the property.
- **Raised door thresholds** to give a little extra height before water can enter.
- **Waterproof or water-resistant membranes** applied to external walls and below ground level to reduce water ingress through the fabric.
A point worth being honest about: resistance measures have limits. If water sits against a wall for a long time, or rises above roughly 600mm, the structural and seepage pressures can become a problem, and water tends to find its way in through floors, walls and service entries. That's why resistance is usually paired with resilience rather than relied on alone.
Flood resilience and recoverability measures (limiting damage)
Resilience measures assume water gets inside and aim to make that as survivable as possible for the building. Typical measures include:
- **Solid floors with tiled or other water-resistant finishes** instead of timber and carpet.
- **Raised electrical sockets, consumer units, wiring and services**, so the electrics stay above likely flood levels and the property can be reconnected quickly.
- **Water-resistant plaster, lime-based renders or cement board** in place of standard gypsum plasterboard, which disintegrates when wet.
- **Removable fittings**, including doors and lower kitchen units that can be lifted out and refitted.
- **A flood-resilient kitchen**, for example with freestanding or wall-hung units and water-resistant materials rather than fixed chipboard carcasses sat on the floor.
The thinking is simple. After a flood, a resilient building can be cleaned, dried and reoccupied in a fraction of the time, with far less stripping out, replastering and rewiring.
Finished floor levels and freeboard
Before reaching for barriers and tiles, the first and most effective measure is often to raise the building out of harm's way. Setting **finished floor levels above the design flood level** is the cleanest form of mitigation because it removes the problem rather than managing it.
The usual approach is to set the finished floor level with a **freeboard of around 300mm above the design flood level**, where the design flood level itself already includes an allowance for climate change. Freeboard is a safety margin that accounts for uncertainty in the flood modelling, wave action, blockages and similar factors.
Where floor levels genuinely can't be raised — for example in a conversion, an extension matching an existing building, or a tight urban site — the fallback is to protect the building to a sensible height instead. As a rule of thumb, providing resistance and resilience to **around 600mm above the estimated flood level** gives a reasonable degree of protection, combining barriers up to that level with resilient construction inside.
What the guidance and regulations actually say
It's worth being clear about the policy position, because it surprises people.
There are currently **no specific Building Regulations requirements** mandating flood-resilient construction. Building Regulations deal with structural safety, contaminants and moisture in general terms, but there's no Part that says "build this house to resist a flood". What this means in practice is that flood resistance and resilience are usually secured through **planning conditions** rather than building control. If an officer grants consent on a flood-risk site, they'll often attach a condition requiring these measures to be designed in and approved before construction.
For best-practice design, the recognised reference is **CIRIA's Code of Practice for Property Flood Resilience (C790)**, together with its companion guidance. It sets out a structured process — survey, hazard assessment, design, installation and maintenance — for specifying resistance and resilience measures properly, and it's the document most consultants and insurers will expect to see followed.
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Safe access, egress and people
Physical measures protect the building, but planning also cares about people. Your scheme needs to demonstrate **safe access and egress**, meaning occupants can leave, and emergency services can reach the site, during a flood without undue risk. On some sites this is straightforward; on others it drives the layout, the location of doors, or the case for a safe refuge at a higher level.
This is also where it's important not to confuse two different things. Flood resistance and resilience measures are about the **building fabric**. A flood evacuation plan is about **people responding to a flood warning** — who does what, when, and how they get to safety. They work together but they are separate documents, and many applications need both. You can read more on our flood evacuation plan page.
How this fits into a flood risk assessment
Resistance and resilience measures don't exist in isolation. They form part of the mitigation strategy within a flood risk assessment. The FRA establishes the flood depths, the design flood level including climate change, and the residual risk that remains after mitigation. From that, the appropriate package of measures follows — finished floor levels first, then resistance, then resilience, scaled to the actual hazard.
Specifying measures without that underlying analysis tends to produce either over-engineering or, worse, gaps that a consultee will spot. Done properly, the mitigation section reads as a logical response to the risk the assessment has identified. You can see how the wider assessment is structured on our flood risk assessment page.
Get in Touch
If your site needs a flood risk assessment with a clear, proportionate set of resistance and resilience measures, we can help. We work out the real flood hazard at your site and design mitigation that satisfies the LPA and the Environment Agency without gold-plating.
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Get in touch to discuss your site and receive a quote.
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