Large Greenhouses

About our large greenhouses

Large greenhouses offer walk-in growing space that improves how you garden. With models from 10ft to 19ft wide, you get room for proper pathways, diverse planting zones, and comfortable year-round growing. Our collection features box-section aluminium frames with 3mm or 4mm toughened glass. Built to withstand decades of British weather.

Choose from 10ft wide greenhouses, 12ft wide greenhouses, or 14ft wide greenhouses depending on your plot size. Every model includes built-in gutters, roof vents, and double doors wide enough for wheelbarrows. We provide free UK delivery and warranties spanning 10 to 25 years.

Types of large greenhouse we offer

Large greenhouse comparison

* Matt's Pick, best entry into large greenhouses with toughened glass, 20-year warranty, and 100 sq ft growing space

Matt's pick: best large greenhouse for most gardeners Best For: Serious hobby growers stepping up from a 6ft or 8ft greenhouse Why I Recommend It: The Supreme 10x10 is the sweet spot. 100 sq ft of growing space with toughened safety glass. Elite's box-section frame handles wind loads that buckle cheaper structures. I've fitted hundreds of these and the build quality is consistently excellent. 20-year warranty gives you total confidence. Price: £1,999 View Product

How to choose the right size

10Ft wide (10x6ft to 10x12ft)

Well suited to serious hobby growers. Two runs of staging (2ft deep each) with a comfortable 6ft central path. Fits 40-50 tomato plants, 30 pepper plants, or mixed growing with a small propagation area. Annual heating costs around £150 in a cold winter.

12Ft wide (12x8ft to 12x16ft)

The sweet spot for passionate gardeners and semi-commercial growers. Three staging runs or distinct zones, propagation at one end, growing in the middle, overwintering at the far end. Grows 80+ tomato plants or maintains a year-round salad supply for a family of six. Heating costs £250, £350 annually.

14Ft+ wide

Built for commercial operations, plant nurseries, or collectors. Professional fitting takes 2-3 days. Browse our Janssens Greenhouses range for the widest Belgian-engineered models, or explore bespoke greenhouses if standard sizes don't fit your plot.

Aluminium vs timber: which frame material?

Aluminium dominates large greenhouses for good reason. Box-section aluminium provides the strength-to-weight ratio needed for structures holding 100+ glass panes. Zero maintenance, no rot, no warping, and 25+ years of service. Powder coating in silver, green, or black prevents corrosion in coastal areas.

Timber offers better insulation but demands upkeep. Large wooden greenhouses need preservative treatment every 2-3 years. However, wood saves roughly 15% on winter heating costs. Swallow manufactures timber greenhouses in Yorkshire with 12-year rot warranties on ThermoWood frames.

For glazing, toughened glass outperforms polycarbonate at this scale. Glass maintains 90% light transmission for decades and never yellows. Polycarbonate insulates better but degrades under UV over 10-15 years. Our glass vs polycarbonate guide covers the full comparison.

Foundation and siting

You cannot skip the base with a large greenhouse. Structures over 10ft wide need a level, solid foundation. Either a concrete slab or paving slabs on compacted hardcore. An uneven base will twist the frame and prevent doors from closing. Our greenhouse base preparation guide covers DIY methods and costs.

Position where the greenhouse receives 6+ hours of direct sun, with the ridge running east, west for even light distribution. Allow 2ft clearance on all sides for maintenance and gutter cleaning. For structures over 30 sq m (roughly 12x10ft), check planning rules with your local council. Most qualify as permitted development if positioned correctly.

Heating and ventilation

Large greenhouses create microclimates that need active management. In summer, temperatures hit 40°C without adequate ventilation. You need roof vents covering at least 20% of floor area plus louvre vents on opposite walls for cross-flow. Automatic vent openers (from £45 each) save daily trips to open and close. Read our guide to heating a greenhouse for detailed running costs.

Winter heating costs depend on your goals. Keeping frost-free (2-4°C) costs roughly £12, £18 per sq m per winter using electric heaters. Raising temperatures to 10°C for Mediterranean crops multiplies costs by 3-4x. Bubble insulation on internal glazing cuts bills by 30-40% but reduces light. Consider lean-to greenhouses if you want house-wall warmth, they save 25-35% on heating versus freestanding models.

Frequently Asked Questions

• What qualifies as a large greenhouse?

  Any greenhouse 10ft wide or larger counts as "large" in the UK market. Standard greenhouses measure 6ft or 8ft wide, so 10ft+ models offer 50-150% more growing space. Most large greenhouses range from 80 to 200 sq ft of floor area.

• Do I need planning permission for a large greenhouse?

  Most large greenhouses qualify as permitted development. You do not need planning permission if the greenhouse is under 2.5m tall at the eaves and covers less than 50% of your garden. Within 2 metres of a boundary, maximum total height cannot exceed 2.5m. Conservation areas and front gardens have stricter rules, check with your local council.

• How much does a large greenhouse cost?

  Large greenhouses start from around £1,000 for 10ft wide aluminium models. Most customers spend £2,500, £5,000 for a well-specified 12ft greenhouse with delivery. Premium 14ft+ structures with full toughened glass reach £7,000, £19,000. Professional installation adds £400, £1,200 depending on size.

• What base does a large greenhouse need?

  Concrete slabs or paving on compacted hardcore are the only suitable foundations. The base must be level within 10mm across the entire area. It should project 100-150mm beyond the frame on all sides. Budget £300, £800 for materials depending on size. See our concrete base guide for step-by-step instructions.

• How long does a large greenhouse take to build?

  DIY assembly of a 10ft greenhouse takes 2-3 full days for two people. 12ft models need 3-4 days. 14ft+ structures typically require professional installation. Our fitting team completes most large greenhouses in 1-2 days with full warranty compliance.

• Which brands make the best large greenhouses?

  Janssens consistently ranks highest for build quality in large sizes. Some customers report 30+ years of service from Janssens frames. Elite offers excellent value in the £1,500, £4,000 range with 20-year warranties. For timber, Swallow manufactures in Yorkshire with 12-year rot warranties on ThermoWood frames.

• Can I add staging and shelving to a large greenhouse?

  Yes, every product page lists all compatible accessories. You'll see staging, shelving, extra vents, and rainwater kits that fit your chosen model. Select everything in one order. We've been selling greenhouses for over 14 years and list only accessories confirmed to fit. Browse our full greenhouse accessories range.