Two blokes order the same 9m x 12m garaport. One’s in Toowoomba, one’s in Cairns. Same size, same doors, same colour. The bloke in Cairns pays thousands more and gets a shed with heavier steel, more purlins and a lot more concrete in the ground.
Nothing’s gone wrong. That’s wind regions doing their job. Australia gets carved into four zones based on how hard the wind blows where you are, and the zone you’re in changes how a shed has to be built. Here’s what the regions mean, how to work out which one you’re in, and why it moves the price.
What a Wind Region Actually Is
Every shed built in Australia has to be engineered to AS/NZS 1170.2, the wind actions standard. That standard splits the country into four regions, A through D, based on the worst wind the area is expected to cop.
Region A is the mildest and covers most of the country. Region D is the most severe and covers a narrow stretch of the Western Australian coast. B and C sit in between, and C is where tropical cyclones come into it.
The jump between them isn’t small. Region A is designed around a gust of roughly 45 metres per second. Region C is closer to 66, and Region D is around 80. Wind load goes up with the square of the speed, so a Region C shed isn’t carrying 50 percent more force than a Region A one. It’s carrying more than double.
That’s the whole reason two identical looking sheds can be built completely differently.
Which Region Are You In?
Roughly speaking, here’s how it falls.
Region A covers most of inland and southern Australia. Sydney, Melbourne, Brisbane, Adelaide, Perth, Canberra, Hobart, Toowoomba and the vast bulk of the farming country in between. If you’re more than about 100km from the northern coastline, you’re almost certainly in A.
Region B is the transition strip. Think the central Queensland coast around Rockhampton, Gladstone, Bundaberg and Hervey Bay, plus a band running inland from the Region C boundary.
Region C is the cyclone zone. The Queensland coast from roughly Bundaberg north, so Mackay, Townsville and Cairns, along with the Northern Territory coast including Darwin, and the northern WA coast through Broome and Port Hedland.
Region D is the worst of it, a narrow section of the WA coast around Exmouth, Onslow and Carnarvon.
Those are guides, not gospel. The boundaries follow lines on a map in the standard, not council borders, and being 20km the wrong side of one changes your answer. If you’re anywhere near a boundary, your engineer needs to confirm it rather than you eyeballing a map.
You’ll also see sheds and homes described with an N or C rating, like N2 or C2. That’s AS 4055, a simplified housing classification. N ratings are non-cyclonic, C ratings are cyclonic. Shed kits are usually engineered directly to AS/NZS 1170.2 instead, which is more specific, but the two systems are describing the same thing.
Terrain Category: Why Your Neighbour Can Differ
The region sets the baseline. Terrain category adjusts it for what’s actually around your site.
The logic is simple enough. Wind slows down when it has to get past buildings, trees and fences. An open paddock offers it nothing to push against, so the shed cops the full force. A block in the middle of a housing estate is shielded by every house upwind of it.
Categories run from 1 to 4. Category 1 is wide open, exposed flat land or open water. Category 2 is open terrain with scattered obstructions, which is most farmland and acreage. Category 3 is suburban, with houses and trees close together. Category 4 is city centre or heavy industrial.
This is why two people in the same postcode can get different engineering. A shed going up on a bare hilltop on a 10 acre block is a different job to the same shed tucked behind a house in an established suburb. Elevation matters too. Sheds on ridgelines and hill crests get a further uplift because the wind accelerates over the top.
Importance Level: What the Shed Is For
The last piece is what happens if the thing fails, and how many people are around when it does.
Importance level 1 is low consequence. An isolated farm shed out in a paddock, with nobody in it most of the time and nothing next to it, can often be designed to a shorter return period. Level 2 is normal, and covers the vast majority of domestic garages and workshops on residential blocks. Level 3 applies where a lot of people gather, and level 4 is post-disaster stuff like emergency services buildings.
For most people ordering a shed it’ll be level 2. But if you’re putting up a commercial or industrial shed with staff working in it, or something the public will use, it’s worth raising early. It changes the engineering and it changes the quote.
What Actually Changes in the Shed
Move a shed from Region A to Region C and here’s what a decent manufacturer does to it.
The frame gets heavier. Thicker gauge columns and rafters, and often the bays get brought closer together so there’s less span carrying the load. Purlins and girts get spaced tighter for the same reason.
The roof gets tied down properly. Cyclonic fixing assemblies with cyclone washers, closer fastener spacing, and in Region C the cladding has to pass low-high-low fatigue testing under AS 4040.3, because cyclones don’t push once, they push thousands of times over hours. Standard sheeting that holds under a single load can still tear off around the screw heads under repeated cycling.
The footings get bigger. Uplift is usually the governing force on a shed, not downward load, so the job is stopping the whole building from being picked up. That means deeper and wider footings, more concrete and heavier anchor bolts.
Bracing gets heavier through the roof and walls. All of it comes with engineering certification, which the council will want to see with your application either way.
What It Does to the Price
There’s no single multiplier, and anyone who gives you one is guessing.
The increase depends on how far you’re jumping, the size and shape of the shed, your terrain category and how much extra concrete the footings need. A small garage moving from A to B might barely shift. A large open front machinery shed going into Region C is a different build, and the price reflects that.
Worth knowing when you’re comparing quotes: the prices on our shed kit specials page are Region A unless noted. Every reputable supplier quotes to a region, so when two quotes look wildly apart, the first thing to check is whether they’ve been priced to the same one. A cheap quote that’s been done to Region A for a Region C site isn’t cheap. It’s wrong, and council won’t pass it.
How to Find Out Before You Get Quoted
You don’t need to work this out yourself, and you shouldn’t try to.
Your local council can tell you the wind region for your address, and most in cyclone areas publish it. A structural engineer will confirm the region, terrain category, importance level and any topographic uplift, and that’s what the certification is based on.
The easier path is to tell your shed supplier where the shed is going before anything else. Address, block size, what’s around it, whether it’s on a rise, and what you’ll use it for. Any supplier worth dealing with will run the classification as part of the quote.
We’re ShedSafe accredited and members of the Australian Steel Institute Steel Sheds Group, so every kit we supply comes with engineer designed plans and certification for your site, not a generic set. If you’re in a cyclone area, our cyclone rated sheds are engineered for it from the start rather than adapted after the fact.
Give us a call on 1300 887 433 with your address and we’ll tell you what region you’re in before we price anything.