Roundups / Large greenhouses 6x6 and over

Grow-your-own · UK product comparison

Best large greenhouses 6x6 and over compared in 2026

If you want room for staging, tomato rows or a proper potting bench, a 6x6 greenhouse is where the choice gets interesting. This roundup covers five larger models priced from £319.00 to £879.00, spread across aluminium, resin and timber frames. Glazing varies too, with twin-wall polycarbonate on the Palram-Canopia models and styrene on the Mercia pair. Weight, warranty length and assembly style differ quite a bit from one to the next, so we have pulled out the points that matter for day-to-day use. This is desk research based on the product details supplied, not hands-on testing.

P&P

Plot & Pot editors
We compare published product details, sizes and materials. These are desk-researched product roundups, not hands-on tests.

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Our stand-out pick

Palram-Canopia Mythos 6x6 Greenhouse, Silver

The Palram-Canopia Mythos 6x6 Greenhouse, Silver is our pick on paper. At £334.00 it is one of the two cheapest here, and it packs in a hinged lockable door, a roof vent, gutters and a galvanised steel base. The rust-resistant aluminium frame keeps the weight down to 34.1 kg, and the 5-year defects and workmanship warranty has no retreatment conditions attached. Larger or longer-warrantied options exist, but none of them offers this mix of features at this price. This choice comes from comparing the supplied facts, not from testing.

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At a glance

Our picks compared

Prices are dated snapshots and can change. Product dimensions are shown as width × depth × height.

Product	Brand	Price snapshot	Retailer	Dimensions	Weight	Frame	Glazing	Door	Ventilation	Extras	Assembly	Warranty	Roof glazing	Wall glazing	Floor
Palram-Canopia Mythos 6x6 Greenhouse, Silver	Palram-Canopia	£334.00	One Garden	185 × 186 × 208 cm	34.1 kg	Rust-resistant aluminium	Twin-wall polycarbonate	Hinged lockable door	1 roof vent	Gutters and galvanised steel base	Self-assembly, 2 people, 4 to 6 hours	5-year defects and workmanship	—	—	—
Palram-Canopia Mythos 6x8 Greenhouse, Silver	Palram-Canopia	£319.00	One Garden	185 × 247 × 208 cm	39.1 kg	Rust-resistant aluminium	Twin-wall polycarbonate	Hinged door	1 opening window	—	Self-assembly, 2 people, 4 to 6 hours	5-year defects and workmanship	—	—	—
Palram-Canopia Eco Grow 6x6 Greenhouse	Palram-Canopia	£879.00	One Garden	204 × 201 × 198 cm	54.7 kg	Green resin	—	Hinged door	1 roof vent	—	No-tool self-assembly	7-year defects and workmanship	4 mm twin-wall polycarbonate	6 mm twin-wall polycarbonate	—
Mercia Traditional Greenhouse 6x6	Mercia	£779.99	One Garden	192.8 × 182.4 × 206 cm	111 kg	Dip-treated shiplap timber	Styrene	Hinged single door	1 opening roof vent	—	Self-assembly, 2 people, 4 to 6 hours	Conditional 10-year anti-rot, annual retreatment required	—	—	Not supplied
Mercia Traditional Greenhouse 8x6	Mercia	£679.99	One Garden	192.8 × 240.7 × 206 cm	128 kg	Dip-treated shiplap timber	Styrene	Hinged single door	1 opening roof vent	—	Self-assembly, 2 people, 4 to 6 hours	Conditional 10-year anti-rot, annual retreatment required	—	—	Not supplied

The details

Five large greenhouses compared

01 · Best Overall

Palram-Canopia Mythos 6x6 Greenhouse, Silver

A well-equipped aluminium 6x6 with a lockable door, gutters and a steel base for just £334.00.

The Palram-Canopia Mythos 6x6 Greenhouse, Silver combines a rust-resistant aluminium frame with twin-wall polycarbonate glazing, and it comes with a hinged lockable door, a roof vent, gutters and a galvanised steel base. That base is a useful inclusion, as it gives you something to build from straight away. At 34.1 kg it is the lightest of the 6x6 models here, which should make moving the parts around the garden easier. Assembly is a two-person job of around 4 to 6 hours, and the warranty covers defects and workmanship for 5 years. Ventilation comes from a single roof vent, so it is worth thinking about how much airflow you will want in summer.

Price snapshot: £334.00 at One Garden, recorded 2026-11-02. Check the retailer page for the current price.

Key specifications

Dimensions: 185 × 186 × 208 cm
Weight: 34.1 kg
Frame: Rust-resistant aluminium
Glazing: Twin-wall polycarbonate
Door: Hinged lockable door
Ventilation: 1 roof vent
Extras: Gutters and galvanised steel base
Assembly: Self-assembly, 2 people, 4 to 6 hours
Warranty: 5-year defects and workmanship

What stands out

Lockable hinged door, gutters and galvanised steel base all come as part of the package
Light 34.1 kg aluminium frame at a low £334.00 price

Things to consider

Ventilation is limited to a single roof vent
5-year warranty is shorter than the 7-year cover on the Eco Grow

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02 · Best Budget Long Greenhouse

Palram-Canopia Mythos 6x8 Greenhouse, Silver

The cheapest greenhouse here at £319.00, and the longest of the aluminium models at 247 cm.

The Palram-Canopia Mythos 6x8 Greenhouse, Silver stretches the Mythos design to 247 cm in length, which gives you plenty of space for growing beds along the sides. It uses a rust-resistant aluminium frame with twin-wall polycarbonate glazing, a hinged door and one opening window. Weighing 39.1 kg, it is still light compared with the timber models. It costs £15 less than the 6x6 Mythos, though it does not list the gutters or steel base that the smaller model includes, and the single opening window is the only vent. Assembly takes two people around 4 to 6 hours, with a 5-year defects and workmanship warranty.

Price snapshot: £319.00 at One Garden, recorded 2026-11-02. Check the retailer page for the current price.

Key specifications

Dimensions: 185 × 247 × 208 cm
Weight: 39.1 kg
Frame: Rust-resistant aluminium
Glazing: Twin-wall polycarbonate
Door: Hinged door
Ventilation: 1 opening window
Assembly: Self-assembly, 2 people, 4 to 6 hours
Warranty: 5-year defects and workmanship

What stands out

Longest aluminium greenhouse here at 247 cm, yet the lowest price at £319.00
Light frame at 39.1 kg for a greenhouse of this length

Things to consider

Ventilation is one opening window only, with no roof vent
Does not include the gutters or steel base that come with the 6x6 Mythos

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03 · Best for Long Warranty and Easy Build

Palram-Canopia Eco Grow 6x6 Greenhouse

A resin-framed 6x6 with thicker wall panels, a 7-year warranty and tool-free assembly, though it is the priciest option at £879.00.

The Palram-Canopia Eco Grow 6x6 Greenhouse stands apart from the rest with its green resin frame and its mix of 4 mm twin-wall polycarbonate on the roof and 6 mm panels on the sides. The thicker side panels are a point worth noting if you are comparing glazing across the group. Assembly is described as no-tool, which will suit anyone who would rather not hunt for spanners. It has a hinged door and one roof vent, a 204 x 201 cm footprint and a 7-year defects and workmanship warranty, the longest warranty of the non-timber models. At £879.00 it costs well over double the aluminium Mythos models.

Price snapshot: £879.00 at One Garden, recorded 2026-11-02. Check the retailer page for the current price.

Key specifications

Dimensions: 204 × 201 × 198 cm
Weight: 54.7 kg
Frame: Green resin
Roof glazing: 4 mm twin-wall polycarbonate
Wall glazing: 6 mm twin-wall polycarbonate
Door: Hinged door
Ventilation: 1 roof vent
Assembly: No-tool self-assembly
Warranty: 7-year defects and workmanship

What stands out

No-tool self-assembly and a 7-year defects and workmanship warranty
6 mm twin-wall side panels under a 4 mm twin-wall roof

Things to consider

Most expensive model here at £879.00
Only one roof vent despite the larger 204 x 201 cm footprint

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04 · Best for Traditional Timber Looks

Mercia Traditional Greenhouse 6x6

A classic shiplap timber 6x6 with a roof vent, but it costs more than the bigger Mercia 8x6.

The Mercia Traditional Greenhouse 6x6 suits gardeners who prefer the look of timber, with dip-treated shiplap framing and styrene glazing. It stands 206 cm tall and has a hinged single door and an opening roof vent. At 111 kg it is far heavier than the aluminium models, so it will feel more substantial but is harder to shift around. No floor is supplied, so you would need to plan a base. The 10-year anti-rot warranty is conditional and requires annual retreatment. At £779.99 it costs £100 more than the larger Mercia 8x6, which makes it a hard one to justify on size and price alone.

Price snapshot: £779.99 at One Garden, recorded 2026-11-02. Check the retailer page for the current price.

Key specifications

Dimensions: 192.8 × 182.4 × 206 cm
Weight: 111 kg
Frame: Dip-treated shiplap timber
Glazing: Styrene
Door: Hinged single door
Ventilation: 1 opening roof vent
Floor: Not supplied
Assembly: Self-assembly, 2 people, 4 to 6 hours
Warranty: Conditional 10-year anti-rot, annual retreatment required

What stands out

Dip-treated shiplap timber frame gives a traditional look
Opening roof vent and hinged single door at 206 cm tall

Things to consider

£779.99 is £100 more than the larger Mercia 8x6
10-year anti-rot warranty is conditional on annual retreatment, and no floor is supplied

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05 · Best Large Timber Option

Mercia Traditional Greenhouse 8x6

The biggest timber greenhouse in the group, and £100 cheaper than the smaller Mercia 6x6 at £679.99.

The Mercia Traditional Greenhouse 8x6 offers the longest footprint among the timber models at 240.7 cm, with the same dip-treated shiplap frame, styrene glazing, hinged single door and opening roof vent as its smaller sibling. It is the heaviest greenhouse in this roundup at 128 kg, and assembly is a two-person job of around 4 to 6 hours. No floor is supplied, and the 10-year anti-rot warranty only applies if you retreat the timber each year. Even so, at £679.99 it undercuts the Mercia 6x6 while giving you more floor space, which makes it the more sensible of the two timber options.

Price snapshot: £679.99 at One Garden, recorded 2026-11-02. Check the retailer page for the current price.

Key specifications

Dimensions: 192.8 × 240.7 × 206 cm
Weight: 128 kg
Frame: Dip-treated shiplap timber
Glazing: Styrene
Door: Hinged single door
Ventilation: 1 opening roof vent
Floor: Not supplied
Assembly: Self-assembly, 2 people, 4 to 6 hours
Warranty: Conditional 10-year anti-rot, annual retreatment required

What stands out

240.7 cm length gives the most room of the timber models
£100 cheaper than the smaller Mercia 6x6

Things to consider

Heaviest model here at 128 kg
Anti-rot warranty is conditional on annual retreatment, and no floor is supplied

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