Water is getting under your garage door. The solution is a demountable aluminium flood barrier: slim side rails fixed permanently either side of the opening, and lightweight removable panels that slot into them to hold floodwater back.
It is made to measure for your opening, it goes in within minutes of a flood alert, it is reusable across as many events as you need, and it protects the garage door itself as well as the content inside.
This guide covers what the barrier does, how to work out the width you need, what suits your type of garage door, and the one thing about garage walls that most people miss.
The barrier at a glance
How a garage door flood barrier works
The barrier fits across the outside of the garage opening. Two slim aluminium rails are fixed permanently into the masonry either side of the door. Day to day that is all that is in place, so you keep full use of the garage and there is nothing across the opening.
When flooding is forecast, the panels slot down into the rails. They compress against seals in the rails and against the floor, forming a continuous line across the opening that holds water back.
Flood Protection Solutions supplies two systems for garage doors, the FPS Flood Barrier and the Nautilus Flood Barrier. Both are aluminium, and both are cut to the measured width of your opening. Standard sizes include the Nautilus 200 at 0.6m high by 1m wide for a single door and the Nautilus 400 at 0.4m high by 1.8m wide for a double, though most garages take a made to measure barrier because few openings are a standard size.
It protects the door, not just the doorway
This is worth spelling out, because it is the part people do not expect.
A garage door is a large, relatively light panel. Under water load it can deflect, and the tracks, springs, rollers and any electric operator are not designed to be submerged. Because the barrier sits outside the opening, floodwater never reaches the door at all.
Replacing a flood damaged sectional or roller door, and its mechanism, is a significant cost on its own, a barrier avoids this.
Fitting the panels in advance
A barrier does not have to be deployed at the last minute.
Most households fit the panels as soon as a flood alert is issued and leave them in for as long as the risk lasts. If you are going away during a wet spell, fit them before you go. Through a bad winter, some people simply leave the barrier up on a garage they are not using daily and lift it out when the weather settles.
Working out what you need
Width and span
Openings up to around 1.5m to 1.8m are normally spanned in one run with nothing in the middle. Most garage doors are wider than that, so a demountable centre post is the usual arrangement.
The post drops into a socket set into the floor, the panels bear onto it, and it lifts out afterwards leaving a flush cover plate. It adds a few seconds to deployment and nothing to the day to day appearance of the garage, and the socket just needs keeping clear of grit and leaves.
Wider postless spans are possible using a specially designed system. It is more industrial in appearance, so it is rarely the right answer on a domestic garage, but it is worth asking about if a clear opening matters, for example on a commercial unit or where a post would obstruct access.
The floor
The bottom seal needs a firm, reasonably smooth line to bear against. Garage floors are usually smooth but the outside could be gravel or block paving which would need a ground strip adding for the rubber seal to compress down, forming a watertight seal.
Drainage also needs to be considered as garages often have aco drains situated in front of them, flood barriers can not sit in front of drains as this can lead to water ingress. Barriers can be fitted internally if drainage can not be moved.
The reveals
Rails need fixing into sound masonry. Two things to check:
- Many up and over doors sit in a steel or timber subframe fixed to the brickwork. The rails fix to the masonry, not the subframe.
- There needs to be enough clear reveal either side of the opening for the rails.
What suits your type of garage door
Up and over doors
Straightforward. The door sits back in the opening, there is normally clear reveal either side for the rails, and the barrier sits proud of the door with plenty of clearance.
Roller shutter doors
Roller doors leave a defined gap under the curtain when closed, and that gap is where water enters. A barrier across the outside of the opening is the right answer, because a roller curtain is not structurally intended to resist water pressure across its full width. The barrier takes the load instead of the shutter.
Sectional doors
Sectional doors usually have the best factory bottom seal of the three types, but that seal is for weather, not flood, and the panel joints are not watertight under pressure. A barrier outside the opening keeps water off the door entirely, which also protects the panel joints and the operator.
Garage walls: why we also recommend internal tanking
This is the part most people miss, and it is specific to garages.
Detached garages are frequently single skin brickwork, and integral garages are commonly cavity walls left bare on the inside, with no plaster and no waterproof finish.
Brick and mortar are porous. If floodwater stands against the outside of a bare masonry wall for several hours, water will come through the wall itself. People are then surprised to find a wet garage floor with a barrier that held perfectly well.
The answer is internal tanking. A waterproofing system is applied to the inside face of the garage walls, and it stops water passing through the masonry while the barrier holds it back outside. The barrier deals with the opening and the tanking deals with the walls. Together they are what actually keeps a garage dry.
We recommend considering tanking where:
- The garage is single skin brickwork
- The walls are bare masonry
- Floodwater is likely to stand for several hours rather than pass through quickly
- The garage is integral to the house, so a wet dividing wall becomes a wet hallway
- The garage is used for anything you would not want damp, including as a store, workshop, utility area or gym
It is best done at the same time as the barrier. You are already having work carried out, and the two measures are designed to complement each other.
What else needs doing at the same time
Sealing the opening and tanking the walls covers the main routes in. A few smaller ones are worth dealing with while the work is happening.
- Air bricks and vents. Anti-flood air bricks close automatically as water rises.
- The wall to floor junction, which needs detailing properly as part of the tanking.
- Pipe and cable penetrations. Waste pipes, cable entries and old redundant holes all need sealing.
- Side doors and the internal door. An integral garage door into the house is rarely a flood door, and its threshold is usually a simple strip.
- Raise the electrics. Move outlets above the design flood level.
- Raise the appliances. Freezers, washing machines and tumble dryers onto plinths.
- A sump pump for seepage and any rainfall that falls inside the protected area.
- Non-return valve on any waste connection serving a utility items.
Appearance and finish
The permanently visible part of the system is just the pair of side rails. Aluminium is standard, but the rails can be powder coated to any RAL colour, so they can be matched to the garage door itself.
Specify the colour when you order, because powder coating happens during manufacture. Our guide to colour matched flood barriers covers the process and the limits.
Post covers are worth having too. They keep weather and debris out of the rail channels, which is the difference between panels that slide in first time and panels you are fighting with in the rain.
Standards and accreditation
Flood resistance products for buildings are covered by BS 851188-1:2019+A1:2021. It sets requirements for designation, testing, factory production control, installation manuals, deployment instructions and marking.
All our barriers are independently tested and certified, and the company is independently accredited and approved by the Environment Agency. Some insurers and grant schemes may want to see this.
No barrier is completely watertight. Standards work to allowable leakage rates rather than zero leakage, which is why a water pump is normally part of the scheme alongside the barrier.
Costs and funding
If your property has been flooded and you are insured with a participating provider, Flood Re’s Build Back Better scheme allows up to £10,000 towards property flood resilience measures as part of the repair, on top of the cost of putting right the damage. Barriers, flood doors, automatic air bricks, non-return valves and sump pumps all qualify. Speak to your insurer before renewing, because what each provider offers differs.
Maintenance
- Keep the rail channels and any post socket clear of grit and leaves
- Check the seals for damage or perishing once a year, lubricate with silicone spray
- Wash powder coated rails down a couple of times a year, more often near the coast
- Deploy the barrier once a year as a dry run, so you know it goes in cleanly and everyone in the house knows how
Why water gets under a garage door
Worth understanding briefly, because it explains why the factory seal on your door has not helped.
Every garage door needs clearance at the bottom to open and close. Manufacturers fit a rubber or brush strip to keep out draughts, leaves and driving rain, and it does that job well. It is not a flood seal and it is not tested or rated as one. Water under pressure finds the gap.
A garage floor is also often the lowest finished level on a property, so water that has not yet reached the front door step may already be spreading across the garage slab.
The Environment Agency’s 2024 National Flood Risk Assessment put around 4.6 million properties in England in areas at risk of surface water flooding, the kind that arrives with little or no warning.
Key takeaways
- A demountable aluminium barrier is the solution for a garage door: permanent side rails, removable panels, made to measure for your opening.
- Single spans of up to five metres are achievable without a centre post, covering almost every domestic single and double garage.
- Common domestic heights run from around 400mm to 600mm, evidenced by a survey rather than guessed.
- The barrier sits outside the opening, so it protects the door, tracks and operator as well as the doorway.
- Panels can be fitted in advance and left in place for as long as the flood risk lasts, so the garage is protected when nobody is home.
- Garages are often single skin or bare cavity walls, so water can pass through the masonry even with the opening sealed. Internal tanking stops that and pairs with the barrier.
- The factory strip on your garage door is a weather seal, not a flood seal.
- Rails can be powder coated to any RAL colour, specified at the point of order.
Frequently asked questions
Can you get a flood barrier for a garage door?
Yes. A demountable aluminium barrier fits across the outside of the opening, with slim side rails fixed permanently into the masonry and lightweight panels that slot in when flooding is forecast. It is made to measure for your opening and reusable across as many flood events as you need.
What stops water coming under my garage door?
A demountable aluminium barrier across the opening. It holds water back outside the door entirely, rather than trying to seal the gap the door needs in order to operate.
How wide a garage door can a flood barrier cover?
Single spans of up to five metres with no centre post, which covers almost all domestic single and double garages. Wider commercial openings use a demountable centre post that seats into a floor socket and lifts out afterwards.
How quickly can it be deployed?
Panels slot in within minutes. In practice most people fit them as soon as an alert is issued rather than waiting, and leave them in until the risk passes.
Does it protect the garage when I am out?
Yes, provided the panels are fitted in advance. Fit them when a flood alert is issued, or before going away during a wet spell, and the garage stays protected while the house is empty.
Next step
To correctly quote a barrier we need some information from you, simply fill out our bespoke quote form and this will provide us with all the information to get you a tailored quote.