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Understanding greenhouse costs in Australia

What a greenhouse costs in Australia in 2026

Backyard greenhouse pricing spreads very widely because the category runs from a $150 zip up plastic shelf unit to a $15,000 glass conservatory. The useful bands for 2026 are these. A mini or lean-to unit under 2m² is $150 to $600. A small hobby greenhouse around 2m by 2m in aluminium with twin-wall polycarbonate is $600 to $1,600. The most common backyard size, roughly 3m by 2.5m, lands at $1,400 to $3,500 for the kit. A large 4m by 3m structure is $3,000 to $6,500, and a 6m by 3m semi-commercial tunnel or framed house runs $6,000 to $14,000. Those figures are the structure only. Add the base, ventilation, shading and any services and a realistic all up figure for a standard backyard greenhouse is $2,500 to $5,000 rather than the kit price on the box.

Glazing is the biggest single cost driver

What you glaze with changes both the price and the lifespan. Reinforced polyethylene film over a steel hoop frame is the cheapest way to enclose a given floor area, at roughly 40 to 50 percent of a polycarbonate build, but the film is a consumable with a three to five year life in Australian UV and it will need replacing on a cycle. Twin-wall polycarbonate at 4mm to 6mm is the mainstream choice and the best value for most home growers, offering good insulation, diffuse light that reduces leaf scorch, and a 10 to 15 year life. Multi-wall polycarbonate at 10mm or more adds meaningful insulation for cold climate growing in Tasmania, the ACT and alpine areas. Toughened safety glass is the premium option, the most attractive, the longest lasting, and the heaviest, which drags a slab requirement along with it.

Frame, base and anchoring

Powder-coated aluminium is the default frame for domestic kits because it is light, does not rot and needs no maintenance. Galvanised steel tube is cheaper per square metre and is what you get on hoop or tunnel houses, and it suits larger footprints. Timber frames in cedar or treated pine look far better and cost 30 to 50 percent more, and they need periodic oiling or sealing. Whatever the frame, the base is not optional. A greenhouse sitting on bare soil will rack out of square as the ground moves, the door will stop latching, and it is the structure most likely to be picked up in a storm. A compacted crusher dust pad with a sleeper or treated timber perimeter costs a few hundred dollars in materials and is adequate for most kits, while a concrete slab at $80 to $150 per square metre is the right answer under a heavy glass structure.

Ventilation, shading and the Australian summer problem

Almost every imported greenhouse design assumes a northern hemisphere climate where the problem is keeping heat in. In most of Australia the problem is the opposite. An unvented greenhouse can exceed 45 degrees on a mild spring day, which will kill seedlings faster than any frost. Plan for total vent area equal to roughly 20 percent of the floor space, split between roof vents and a louvre or door at low level so you get a convective flow rather than a single opening. Automatic vent openers using a wax cylinder need no power, cost $60 to $120 each and open and close on temperature whether you are home or not, which makes them the highest value $200 you will spend on the whole project. Shade cloth at 30 to 50 percent, or a thermal screen, is close behind, and in Perth, Adelaide and inland Queensland it is effectively mandatory over summer.

Council approval, wind and where the thresholds sit

A greenhouse is generally treated as an outbuilding or ancillary structure by Australian councils, and small ones usually fall under exempt or complying development so no approval is needed. The thresholds vary by state and by LGA, but the ones that matter are floor area, commonly capped somewhere between 10m² and 20m², wall or overall height, commonly 2.4m to 3m, and setback from boundaries, often 900mm. A 3m by 2.5m greenhouse at 7.5m² clears almost everywhere. A 4m by 3m at 12m² and a 6m by 3m at 18m² sit on or over the line in a lot of council areas, so check before you buy rather than after you build. Separately, wind region matters. In cyclonic regions across northern Queensland, the NT and northern WA, and on exposed coastal sites generally, an engineered tie-down and anchoring detail is required, and a standard imported kit may not comply as sold.

Running costs and what people forget to budget

The structure is a capital cost, but a greenhouse has a modest running cost too. Film reglazing every three to five years is $200 to $700 depending on size. Shade cloth degrades in UV and wants replacing roughly every five years. If you run a heater through a cold climate winter, even a small 1kW tube heater on a thermostat will add $80 to $250 a season depending on tariff and how cold you keep it. Water is usually plumbed from an existing tap, but running power out to the structure properly, in conduit and on an RCD protected circuit, is licensed electrical work and is typically $700 to $1,500. Factor these in when you compare a cheap film tunnel against a polycarbonate kit, because the tunnel's lower purchase price is partly a deferred cost rather than a saving.

Choosing the right size for what you actually grow

The most common regret is buying too small. A 2m by 2m greenhouse holds one bench down each side and a narrow aisle, which is enough for seed raising and a few pots but not enough to grow anything to maturity inside. If you want to raise seedlings for a vegetable garden, a small kit is perfect and the cheapest sensible entry. If you want to overwinter tender plants, grow tomatoes or chillies through to fruit, or keep a propagation area running year round, the 3m by 2.5m size is the practical minimum. Stepping up one size at purchase usually costs a few hundred dollars, while replacing an undersized structure later costs the entire price again, so decide on the basis of what you intend to grow in three years rather than what you are growing now.