Design the ultimate boat shed with shed designer.

What is a boat shed?

A boat shed is a steel-framed Australian building sized to keep a trailerable boat, the trailer and the outboard motor out of the weather. Most are clad in Colorbond® steel and built from 100% Australian-made BlueScope steel, engineered to AS/NZS 1170.2:2021 wind loading for the actual region (Standards Australia, AS/NZS 1170.2 Structural design actions, Part 2: Wind actions). Different brief from a garaport or a generic shed. The job here is drive-through clearance with the outboard up, a door wide enough for the trailer drawbar to swing in, and a slab that takes the loaded weight without cracking. Coastal builds add a corrosion grade conversation that an inland shed never needs.

ShedDesigner's boat shed templates start at 6 by 9 metres at a 3.6 metre eave for a single 4 to 5 metre runabout on its trailer, step up to 7.5 by 12 metres at 4.2 metres for a 7 to 8 metre half-cab or bowrider with motor up, and 9 by 15 metres or larger at 4.5 to 5.0 metre eaves for a luxury cruiser plus a tow vehicle. Pick the closest template, set your span, length, eave and door, then submit your design once for free comparable quotes from ShedSafe accredited dealers in your region.

Sizing by boat length

Three template sizes cover almost every Australian trailer-boat fleet at home.

• 5 metre runabout, 6 by 9 metres internal, 3.6 metre eave. Single-bay starter for a 4 to 5 metre fishing dinghy, half-cab or runabout with the outboard parked vertical. Trailer drawbar swings in, walk-around clearance on both sides.
• 7 to 8 metre bowrider or centre console, 7.5 by 12 metres, 4.2 metre eave. Wider bay for boats with a beam over 2.5 metres and a T-top or Bimini. Drive in, motor up, deck-wash bay across the back.
• 9 metre plus cruiser plus tow vehicle, 9 by 15 metres, 4.5 to 5.0 metre eave. Luxury trailer cruiser, plate-ally centre console or sport-tower build, with the tow vehicle parked alongside under the same roof.

Door, height and clearance reality

The single most common boat-shed mistake is buying off boat-on-trailer height instead of motor-up clearance.

A 5 metre runabout sits roughly 2.4 to 2.7 metres on its trailer with the outboard down. Tilt the outboard up for storage and that same boat hits 3.0 to 3.4 metres at the cowl tip. T-tops on a centre console add another 300 to 500 mm. The roller door drum eats around 400 to 600 mm above the rough opening, which is what drives the eave call (Designer Sheds, Shed door height: drive-through clearance vs daylight opening). The maths runs: motor-up height + door drum + 200 mm safety margin = the eave you actually need. For a 3.0 metre motor-up dimension, that is a 3.6 metre eave minimum. For a 3.5 metre T-top, plan a 4.2 metre eave.

Door width matters as much as height. A standard trailerable beam is 2.5 metres (the legal maximum for general-access trailers under Heavy Vehicle National Law). Reverse parking with a drawbar swing wants a 3.0 metre wide roller door as the absolute floor and a 3.6 to 4.2 metre opening for anything wider than a 6 metre boat.

For an open-sided carport-style cover, see garaports. For the caravan equivalent build, see caravan shed.

Coastal builds, AS/NZS 1170.2 and marine-grade Colorbond

A boat shed is more likely than any other shed type to sit inside a salt-spray zone. Two engineering questions follow.

Wind region. AS/NZS 1170.2:2021 splits Australia into Regions A, B, C and D, with Region B covering most coastal NSW and southern Queensland, Region C running the cyclone coast of north Queensland, the Northern Territory and the Pilbara, and Region D the most cyclone-exposed pockets up to design wind speeds of 260 km/h (Standards Australia, AS/NZS 1170.2:2021). A ShedSafe accredited dealer engineers the frame and footings to your actual region.

Marine corrosion grade. BlueScope's Technical Bulletin TB-35 classifies coastal sites as calm, exposed or surf based on AS 4312:2008 Atmospheric Corrosivity zones in Australia (BlueScope, TB-35 Australian Salt Marine Classifications). BlueScope recommends COLORBOND Ultra steel in severe marine locations: typically 100 to 200 metres from breaking surf for roofing, and 500 to 800 metres for walling. Beyond those distances standard COLORBOND steel is generally suitable (BlueScope Technical Bulletin TB-35). Distances are measured from the high water mark. For very severe sites within about 100 metres of surf, SUPERDURA® stainless steel is the step up. Specify the grade upfront, before the cladding is rolled.

Slab, washdown, stormwater and power

Four trade-offs worth getting right at the design stage, not after the slab is poured.

Slab. A loaded trailer plus a 5 metre fibreglass runabout runs around 1.5 to 2 tonnes through four wheels and a jockey. A loaded 7 to 8 metre boat plus trailer runs 3 to 5 tonnes. 100 mm of reinforced concrete handles the runabout. Step to 125 to 150 mm with SL82 mesh for the heavier rig. AS 2870 Residential slabs and footings and AS 3600 Concrete structures cover the engineering.

Washdown and stormwater. A wash-out bay on a graded slab needs a 1 in 80 fall to a grated drain and discharge to legal stormwater under AS/NZS 3500.3 Plumbing and drainage, Part 3: Stormwater drainage (Standards Australia). Ask the dealer to quote the drainage at design time so the plumbing trench goes in once.

Power. A 32 amp single-phase circuit handles a battery charger, a compressor, a deck-wash pump and lighting for most home boat sheds. Three-phase only kicks in for large shed homes that double as a workshop.

Before you get quotes

A boat shed sits on the title for 30 years. The boat inside it is one of the most expensive movable assets a household owns.

100% Australian-made BlueScope steel across structural framing and Colorbond® cladding. BlueScope's COLORBOND® steel cladding for sheds and garages carries a warranty of up to 15 years against corrosion to perforation, with the exact period set by location and application (BlueScope, Garages & Sheds Warranty). Check your build on BlueScope's online warranty estimator. Marine-grade product carries its own published warranty schedule.

ShedSafe accredited dealers, no exceptions. Every dealer on ShedDesigner is ShedSafe accredited under the Australian Steel Institute programme, which independently verifies dealer engineering against AS/NZS 1170.2 and the National Construction Code.

One design, multiple quotes. Your design goes out to dealers covering your region. Every quote prices the same boat shed, in the same steel, to the same wind region and corrosion grade, so the quotes you get back are directly comparable.

Insurance angle worth knowing. Club Marine offers a no-claim bonus of up to 25 per cent off the policy and a lay-up storage discount of up to 60 per cent (5 per cent for each month nominated) when a trailerable boat is stored in an enclosed garage or shed (Club Marine, Tips to save on boat insurance costs). Secured undercover storage often pays the shed off across the boat's ownership cycle.

For the broader category, see sheds. For a coastal colour pick, see Surfmist Colorbond or Dune Colorbond.