What Size Greenhouse Do I Need? UK Guide from Expert Installers
UK greenhouse sizes range from 6x4ft (24 sq ft) to 10x12ft (120 sq ft) and beyond. A 6x4ft greenhouse holds around 4 tomato plants and costs from £395. The most popular size is 8x6ft (48 sq ft). It fits 8-10 tomato plants with staging on both sides and starts at £509. After fitting over 3,000 greenhouses since 2012, we find 65% of returning customers wish they had bought one size larger.
Key Takeaways
- 8x6ft is the sweet spot — 48 sq ft with staging on both sides and room for 8-10 tomato plants
- Go one size up — 65% of returning customers wish they had bought bigger
- Internal width matters more than footprint — after staging, a 6ft-wide greenhouse leaves only 540mm of path
- Cost per sq ft drops with size — an 8x6 is ~£11/sq ft versus ~£16/sq ft for a 6x4
Installer's Note
We have fitted over 3,000 greenhouses since 2012. The single most common thing customers tell us on the second visit? "I should have gone bigger." A 6x4 feels spacious in March. By July, it is packed. If your garden can take an 8x6, start there. You will thank yourself when the tomato season arrives.
Why most gardeners buy too small
65% of our returning customers buy a larger greenhouse the second time around. The pattern is always the same. They start with a 6x4ft because the footprint feels safe. By midsummer, every shelf is packed. Grow bags line the floor. There is nowhere to pot on seedlings.
The problem is not ambition. Greenhouses fill up faster than people expect. Four tomato plants, two cucumber vines, a shelf of seedlings, and a propagator. That is a 6x4 at full capacity. Add staging to both sides and the usable floor space shrinks to the size of a bath mat.
We always tell customers the same thing: measure your available space, then buy the biggest that fits. The price difference between sizes is smaller than you think. Read our guide to the best beginner greenhouse if you are starting from scratch.
Greenhouse sizes explained: what fits in each
6x4ft: the starter (24 sq ft)
A 6x4ft greenhouse measures roughly 1930mm x 1320mm inside. That fits one row of staging, 4 tomato plants in grow bags, or a couple of seed trays. It suits a small patio or courtyard where space is genuinely limited.
Best for: windowsill-to-greenhouse upgrades, seed starting in spring, and overwintering a few tender plants. If this sounds like your garden, read Think Your Garden Is Too Small for a Greenhouse? for layout ideas.
Our 6x4ft greenhouses start from £395.
6x8ft or 8x6ft: the sweet spot (48 sq ft)
This is the size we recommend most often. An 8x6ft greenhouse (1930mm x 2570mm) gives you staging on both sides with a 540mm central path. That is enough room to work without knocking plants off shelves.
You can grow 8-10 tomato plants, keep a propagator running, and still have floor space for grow bags. Start 200+ seedlings in spring without running out of bench room. The air volume prevents the rapid temperature swings that stress plants in smaller structures.
Weighing up glazing? Our glass vs polycarbonate comparison covers the detail.
Our 8x6ft greenhouses start from £509.
8x10ft: the serious grower (80 sq ft)
At 2570mm x 3220mm, an 8x10ft gives you proper room. You get two full-length staging benches, a ground-level bed on one side, and space to move without brushing past plants. You can run separate warm and cool zones using a partition.
This is the size we recommend for anyone growing year-round. Overwintering takes bench space all through autumn and winter. If you plan to heat through the cold months, you need that extra square footage to justify the running costs.
Our 8x10ft greenhouses start from £1,099.
10x12ft and above: the full growing operation
At 120+ sq ft, you are into serious horticulture territory. These greenhouses suit allotment growers and keen propagators. If you want to supply the neighbours with tomatoes all summer, this is where you start.
The internal width of a 10ft greenhouse (roughly 3150mm) lets you run three rows. Staging on both sides plus a central ground bed or a third bench. It is a completely different growing experience compared to a 6ft or 8ft frame.
How many plants fit in each greenhouse size?
This table is based on standard 450mm-wide staging on each side. Ground-level grow bags sit in the remaining floor space. These are real numbers from greenhouses we have installed and set up for customers.
| Size | Floor area | Tomato plants | Seed trays (half-size) | Staging layout |
|---|---|---|---|---|
| 6x4ft | 24 sq ft | 4 | 6-8 | 1 side only |
| 6x8ft | 48 sq ft | 8-10 | 16-20 | Both sides |
| 8x6ft | 48 sq ft | 8-10 | 16-20 | Both sides |
| 8x10ft | 80 sq ft | 16-20 | 30-40 | Both sides + central bed |
| 10x12ft | 120 sq ft | 24-30 | 50+ | Both sides + central bed |
Our guide to growing tomatoes in a greenhouse has more on maximising your crop.
Usable space after staging: the number that actually matters
Nobody else publishes this data. After fitting staging, your usable path width drops significantly. This is the single most important measurement when choosing a greenhouse width.
| Greenhouse width | Staging (both sides) | Path width remaining | What that feels like |
|---|---|---|---|
| 6ft (1930mm) | 2 x 450mm | 540mm | Width of a kitchen drawer unit. Single file only. |
| 8ft (2570mm) | 2 x 450mm | 1170mm | Comfortable working space. Room to crouch and pot. |
| 8ft (2570mm) | 2 x 600mm | 870mm | Still workable with wider staging shelves. |
| 10ft (3150mm) | 2 x 600mm | 1350mm | Room for a central bed or third bench. |
That 540mm path in a 6ft greenhouse is tight. You can walk through, but crouching to pot plants or reach lower shelves is awkward. This is the main reason we push customers towards 8ft wide when their garden allows it.
Matt's Tip: Measure the path, not the floor
Before you buy, lay two objects 450mm wide on the ground, 540mm apart, and try to work between them. If it feels cramped, you need an 8ft-wide greenhouse. I have lost count of how many customers ring after assembly wishing they had gone from 6ft to 8ft wide. The extra 640mm of path width changes everything.
How to choose the right size for your garden
Three questions settle the decision:
- What is the largest footprint your garden can take? Measure the space and leave 450mm clearance around all sides for guttering, cleaning access, and airflow.
- What do you want to grow? Tomatoes and cucumbers need floor space for grow bags. Seedlings and herbs need staging. Year-round growing needs both.
- Will you use it all year? Winter growing takes permanent bench space. If you plan to heat through winter, add one size up from what feels "enough" for summer alone.
Once you have settled on a size, you will need a base. We have step-by-step guides for building a concrete greenhouse base and a paving slab base.
Getting the position right matters as much as the size. Our guide to the best position for a greenhouse covers orientation, sunlight, and wind shelter.
Is a lean-to greenhouse big enough?
Lean-to greenhouses attach to a house or garden wall. They are narrower than freestanding models (typically 4ft deep) but they benefit from the thermal mass of the wall. Bricks absorb daytime heat and radiate it overnight. This can cut winter heating costs by 20-30%.
A 4x6ft lean-to gives you around 24 sq ft. That matches a freestanding 6x4 in floor area. The wall side retains heat better. This makes lean-tos ideal for overwintering tender plants and starting seeds early.
If you have a south or south-west facing wall, a lean-to is worth considering even in a larger garden. Browse our lean-to greenhouses to see the range.
Cost per square foot: why bigger is better value
| Greenhouse size | Starting price | Floor area | Cost per sq ft |
|---|---|---|---|
| 6x4ft | £395 | 24 sq ft | ~£16 |
| 8x6ft | £509 | 48 sq ft | ~£11 |
| 8x10ft | £1,099 | 80 sq ft | ~£14 |
The 8x6ft is the best value in our range. You get double the floor space of a 6x4 for around 30% more money. The 8x10 costs more per square foot because of its heavier frame. For serious growers, the extra space pays for itself.
Browse our full range of greenhouses to compare sizes and prices.
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Matt's Pick for best value starter greenhouseBest For: First-time owners who want room to grow Why I Recommend It: I have installed hundreds of these. The Venus 5000 has been our best seller since 2012 with a return rate below 2%. At 8x6ft you get staging on both sides, 8-10 tomato plants, and a path wide enough to actually work in. Toughened glass means no worrying about breakage. Price: £629 |
Frequently asked questions
What is the most popular greenhouse size in the UK?
The 8x6ft (48 sq ft) is the most popular greenhouse size. It balances growing space with a manageable footprint. An 8x6 fits staging on both sides with room to work in the centre. We sell more 8x6 greenhouses than any other single size.
Can I put a greenhouse in a small garden?
Yes, a 6x4ft greenhouse needs just 2.8m x 2.2m of ground. Add 450mm around each side for guttering and access. That totals roughly 3.7m x 3.1m. If that is still too large, a lean-to greenhouse against a wall needs only 1.2m of depth.
Is a 6x4 greenhouse big enough for tomatoes?
A 6x4 holds around 4 tomato plants in grow bags. That is enough for a small household. If you also want to grow cucumbers, herbs, or start seedlings, you will run out of space by midsummer. An 8x6 gives you double the growing area for around 30% more cost.
Do I need planning permission for a greenhouse?
Most greenhouses do not need planning permission in England and Wales. Under permitted development rules, you can build up to 2.5m tall within 2m of a boundary, or up to 4m tall further away. The greenhouse must not cover more than 50% of your garden. Rules differ in conservation areas and Scotland.
How much does an 8x6 greenhouse cost?
An 8x6 greenhouse starts from around £509 with horticultural glass. Toughened glass models start from around £629. Premium brands with thicker frames and higher eaves start from around £675. Professional installation is available as an add-on.
