Nød- og brandkøretøjers adgang på græsarealer
En brandvej der virker den dag, den skal bruges – og er usynlig resten af tiden
Redningskøretøjers adgangsveje behøver ikke se ud som veje. IBRAN-gitre bærer tungt køretøjslast under en græsoverflade, så en godkendt adgangsvej kan ligge i plæne, beplantning eller parkeringsareal uden at fremstå som befæstet areal.
Hvorfor armering er afgørende her
En brandvej er en overflade, der skal fungere fejlfrit den ene dag, den bruges – og som i mellemtiden næsten aldrig køres på. Det er en vanskelig opgave. Anlægger man den i asfalt, har man en vej henover landskabet, der ikke tjener noget dagligt formål. Lader man det være ubefæstet græs, risikerer man, at overfladen ikke kan bære køretøjet, når det virkelig gælder.
Et cellegitter løser problemet. Gitteret og det indesluttede rodzone bærer lasten og fordeler den over hele overfladen frem for at koncentrere den under hvert hjul, mens græsset vokser op gennem og over cellerne. Adgangsvejen forbliver grøn, kan slås med plæneklipper og er uadskillelig fra det omgivende landskab – og den er til rådighed med fuld bæreevne i det øjeblik, et køretøj kører ind på den.
Den er også tilgængelig hele året. En uarmeret græsoverflade kan kun bruges i tørre forhold, og brande venter ikke på sommervejret.
Typiske anvendelser
- Adgangsveje og vendepladser for redningskøretøjer
- Opstillingspladser for pumpe- og stigevogne
- Sekundære og nødadgangsveje på byggepladser
- Hospitaler, plejehjem og skoler
- Hoteller, event-venues og turistattraktioner
- Boligudstykninger og etageboligprojekter
- Fredede og bevaringsværdige arealer, hvor en befæstet vej ikke er acceptabel
- Landejendomme og ejendomme med lang adgangsvej
Hvad adgangsvejen skal opfylde
Kravene til redningskøretøjers adgangsforhold fremgår af bygningsreglementet og de lokale beredskabsmyndigheders vejledninger. Kravene måles på geometri og bæreevne – ikke på belægningstype – og det er præcis derfor, en armeret græsoverflade kan opfylde dem.
De typisk angivne mål for en pumpevogn er en frikiøringsbredde på mindst 3,7 m, en portbredde på mindst 3,1 m, en vendediameter på 16,8 m målt mellem kantsten eller 19,2 m målt mellem vægge samt en frihøjde på mindst 3,7 m. Adgangsvejen, herunder eventuelle dæksler, skal have en minimumsbelastningsevne på 12,5 tons for en pumpevogn; for stigevogne gælder højere værdier, der varierer fra myndighed til myndighed.
Hvad angår placering, skal der være køreadgang for en pumpevogn til inden for 45 m fra alle punkter i en énfamiliebolig; for etageboliger og andre bygningstyper gælder særskilte bestemmelser. Stigningsforhold er ligeledes begrænsede: adgangsveje for redningskøretøjer må ikke have en hældning på mere end 1:4.
To ting følger heraf. For det første skal opbygningen dimensioneres til en specifik bæreevne, så dette er et projekteringsopgave og ikke en anlægsgartnersag. For det andet er ovenstående tal kun et udgangspunkt: kravene varierer efter bygningstype, køretøjstype og myndighed, så inddrag byggesagsbehandler og beredskabsmyndighed tidligt i processen. Vi kan levere tekniske data for opbygningen, når du ved, hvad adgangsvejen skal bære.
Oversigt
| Bærelag / subbase | Dimensioneres efter den krævede bæreevne. Typisk 150–250 mm åbengraderet bærelag |
| Fyld | Sandbaseret rodzone til græs, eller 6–20 mm graderet grusmix til grusfyldte sektioner |
| Typisk belastning | Pumpe- og stigevogne samt daglig drifts- og servicetrafik |
| Udseende | Fremstår som græs. Kan slås med plæneklipper og er sammenhængende med det omgivende landskab |
| Tilgængelighed | Fuld bæreevne hele året, også i våde forhold |
| Permeabilitet | Fuldt permeabel. Tæller som vegeteret overflade frem for befæstet areal |
| Designlevetid | 25 år ved dokumenteret udførelse |
| Materiale | 100% genanvendt polypropylen, fremstillet i EU af genanvendt plast |
Hvilken gitterdybde?
Valget af gitterdybde handler om, hvor dybt det indesluttede lag er – og på en nødadgangsvej følger det valg direkte af den bæreevne, projektet kræver.
- IBRAN®-X50 er vores anbefaling til brandveje. Belastningerne er høje, overfladen skal fungere uden varsel, og græs over en dybere rodzone restituerer bedre mellem den daglige slåning og servicetrafik.
- IBRAN®-X40 hvor en lettere sekundær adgangsvej er specificeret, eller den samme overflade også bruges til grus andetsteds på projektet.
- IBRAN®-X30 hvor niveauforhold er begrænsende, eller udgravningsdybden er begrænset af ledninger eller rodzonebeskyttelse.
På en nødadgangsvej vælges altid den tungere løsning, når der er et valg. Denne overflades hele værdi ligger i, at den virker første gang, den bliver bedt om det.
Valg af fyldmateriale
Til græs anvendes en sandbaseret rodzone fyldt i niveau med cellernes overkant – ikke muld alene. Muld holder på vand og komprimeres, og en komprimeret rodzone giver svagere græs præcis der, hvor adgangsvejen skal forblive grøn og synlig.
Specificér en slidstærk brugsplæneblanding frem for en fin prydplæneblanding. Adgangsvejen vil blive udsat for plæneklippere, lejligvis servicekørsel og periodiske øvelseskørsler fra beredskabet, og den skal kunne tåle det.
Hvor en del af adgangsvejen også fungerer som vendeplads, opstillingsplads eller standplads for støtteben, kan det overvejes at bruge et 6–20 mm graderet grusmix i stedet for rodzone i den sektion. Samme gitter, samme færdigt niveau – men en stenopfyldt celle giver en fastere og mere forudsigelig overflade præcis der, hvor belastningerne er størst.
How it goes in
- Agree the route geometry and required carrying capacity with building control and the fire authority before anything is set out. Everything below follows from that number.
- Set out the route and establish falls, then strip turf and topsoil down to a firm formation, removing soft spots rather than building over them.
- Lay a woven geotextile across the formation, lapping joins by at least 300mm, so the sub-base and the subsoil cannot mix.
- Lay and compact an open-graded sub-base in 50mm layers, to the depth your carrying capacity requires. Compacting the full depth in one pass does not work whatever the machine.
- Blind with a thin levelling layer and screed it flat.
- Push-fit the grids together across the full route width, staggering the joints. Cut around drainage, lighting columns and tree pits with a jigsaw or fine-tooth saw.
- Restrain every open edge along the full length. On a route that reads as lawn, the edge is also what stops vehicles straying off the built-up section.
- Fill the cells: sand-dominant rootzone for grass sections, a 6-20mm graded blend for hard standings and turning areas. Level with the cell tops, brushed in so no cell is left hollow.
- Seed or turf, water in, and keep traffic off while the sward establishes.
Full step-by-step detail is in our grass grid installation guide.
Outriggers and hard standing
This is the detail most often missed, and it is worth designing for explicitly.
A high reach appliance works on jacks, and a jack concentrates an enormous load into a very small footprint. Published guidance for hard standing puts that at a point load of 8.3kg per square centimetre, on a surface as level as possible and no steeper than 1 in 12, which is a completely different design case from a wheel rolling across a route.
Treat any designated hard standing as its own specification rather than as more of the same route. Use the deeper grid, fill those cells with a graded stone blend rather than rootzone, and check the gradient. Grass elsewhere on the route is fine; grass under a jack is not the place to economise.
Keeping the route identifiable
A fire route that nobody can see is a fire route that gets blocked, parked on, or planted over three years after handover.
Because a grass route is deliberately invisible, mark it in a way that survives. Options that work: a contrasting gravel edge strip running the length of the route, markers fixed into the grid at intervals, or bollards and signage at the entry point. Whichever you choose, record it on the site plan and in the building's fire strategy so it is still known about when the people who built it have moved on.
It also needs keeping clear. Skips, deliveries, staff parking and new planting all tend to migrate onto the one part of the site that looks like spare lawn.
Maintenance
Almost none, but it needs to be somebody's job.
Mow it with the surrounding grass; mowers pass straight over because the cell tops sit below the growing crown. Feed and overseed as you would any amenity grass, and check levels after the first winter, brushing any settled cells back up.
Worth adding to the grounds contract explicitly, and worth including in the annual fire strategy review: an inspection walk that confirms the route is clear, unobstructed and still in good condition costs ten minutes and is the difference between a compliant route and a theoretical one.
Get it right first time
The one thing worth knowing: design to the carrying capacity, not to the surface.
It is easy to think of this as a landscaping decision, because the finished result looks like lawn. It is not. The route has a number attached to it, that number came from Approved Document B and your fire authority, and everything from excavation depth to sub-base grade to grid depth follows from it.
Get the specification agreed before the drawings are fixed. Retrofitting a compliant route into a finished landscape scheme costs several times what building it correctly would have, and the conversation with building control is considerably less comfortable.
Ask our engineer
Questions about carrying capacity, sub-base depth, hard standings or meeting a fire authority requirement? Ask below, or get in touch directly.
Design your surface
Set out the area, choose a grid and an infill, and see the finished surface. The schedule and the specification follow.
Permeable surface specification
Schedule
Assumptions
Specification
Common Questions
Can a fire appliance route be grass rather than tarmac?
Yes. Fire service access is assessed on geometry and carrying capacity rather than on what the route is surfaced with, so a reinforced grass route designed to the required capacity can satisfy the requirement while reading as landscape.
Agree the specification with building control and the fire authority before setting out, because the required carrying capacity determines the whole build-up.
What carrying capacity does a fire access route need?
Commonly published guidance gives a minimum carrying capacity of 12.5 tonnes for a pumping appliance route, including manhole covers and similar. Figures for high reach appliances are higher and vary between authorities.
Requirements differ by building type and appliance, so confirm the number with your fire authority and building control rather than assuming.
How wide does a fire appliance access route need to be?
Commonly published figures for a pumping appliance are a minimum road width between kerbs of 3.7m, a minimum gateway width of 3.1m, a turning circle of 16.8m between kerbs or 19.2m between walls, and a minimum clearance height of 3.7m.
High reach appliances need larger turning circles and greater clearance height. Confirm the geometry with your fire authority.
Will a grass fire route work in wet conditions?
That is the main reason to reinforce it. An unreinforced grass route is only usable in dry conditions, and fires do not wait for good weather.
A cellular grid confines the rootzone so it cannot shear into ruts, and the surface stays fully permeable so water drains through rather than standing on top. The route is at full strength year-round.
What about outriggers and jacking points?
Hard standing for a high reach appliance is a different design case from a route. Guidance puts the requirement at a point load of 8.3kg per square centimetre, on a surface as level as possible and no steeper than 1 in 12.
Treat any designated hard standing as its own specification: use the deeper grid and fill those cells with a graded stone blend rather than rootzone.
Which grid depth should a fire access route use?
The 50mm grid is our recommendation for fire appliance routes. Appliance loads are high, the surface has to perform without warning, and grass over a deeper rootzone recovers better from the mowing and service traffic it sees day to day.
Where there is a choice, take the heavier duty option. This is a surface whose whole value is that it works the first time it is asked to.
How do you stop people parking on or blocking a grass fire route?
Mark it in a way that survives handover. A contrasting gravel edge strip along the route, markers fixed into the grid at intervals, or bollards and signage at the entry point all work.
Record the route on the site plan and in the building's fire strategy so it is still known about years later, and include an inspection in the annual fire strategy review.
Can the route be used for anything else day to day?
Yes, and it usually should be. A reinforced grass route can double as lawn, overflow parking, an events area or a service vehicle route, which is what makes it worth building compared with a road that sits unused.
Just keep it unobstructed: anything semi-permanent placed on it, from planters to skips to a bike store, compromises the access it exists to provide.
How steep can a fire access route be?
Guidance limits access roads used by fire appliances to a gradient no steeper than 1 in 4, and hard standings for high reach appliances to no steeper than 1 in 12.
Confined stone and rootzone hold on gradients that loose material washes off, but the gradient limits are about appliance operation rather than surface stability, so they apply regardless of construction.
What maintenance does a grass fire route need?
Mow it with the surrounding grass, feed and overseed as amenity grass, and check levels after the first winter. Mowers pass straight over because the cell tops sit below the growing crown.
The grid itself needs nothing and carries a 25 year warranty subject to documented installation. The important addition is a periodic check that the route is still clear and unobstructed.
Ask our engineer
Questions about depths, sub-base, edging or which system fits your project? Ask below.
