An aluminium greenhouse gives you a sheltered place to raise seedlings and grow crops such as tomatoes and cucumbers. Start with what you want to grow and how you’ll move around inside. Those two decisions will help you narrow down the size, shape and glazing.
Measure the space you’ll actually use
Mark out the footprint in your garden. Leave room to open the door, carry in bags of compost and clean the outside. Inside, plan a path wide enough to move comfortably past benches or raised beds. If you want to grow climbing plants, check the usable height near the sides as well as at the ridge.
Choose a frame and glazing that suit the site
Aluminium frames don’t need the same routine painting or staining as timber. The glazing affects how the greenhouse feels and how you use it. Clear glass offers an unobstructed view, while some polycarbonate panels diffuse the light. Check the options for the model you’re considering and follow its foundation and anchoring instructions.
Plan ventilation before summer
A greenhouse can warm up quickly in direct sun. Look at where the roof vents and doors sit and whether you can reach them easily. If you’re often away on sunny days, check whether your chosen model supports automatic vent openers.
Freestanding or against a wall?
A freestanding model gives you more flexibility in choosing its position. A lean-to can make good use of a narrow space beside a suitable wall. Compare the footprint, door position and vent layout before deciding.
Explore JUPA KAS aluminium greenhouses.
Compare aluminium greenhouse sizes on the ground
Mark out two sizes with string. Add the width of the beds or table and walk the remaining aisle. If you plan to grow tall tomatoes, look at usable height near the walls as well as ridge height. For a garden room, include space to pull chairs out and open the door.
Choose glazing and ventilation together
Think about how much direct sun the site receives and whether the greenhouse is mainly for growing, seating or both. Compare glazing choices and check the number and position of roof vents on each model. Before ordering, confirm the base dimensions, door opening and delivery access.
Decide what the greenhouse needs to hold
List what you intend to put inside in the first year. For growing, include beds, seed trays, supports and the containers you water most often. For a garden room, list the table, chairs and plants you want to keep around the edges. Measure each item in use. A chair pulled back from a table needs more room than the same chair pushed underneath it. A tomato plant tied to a support takes up more space than the pot it sits in.
Draw a narrow layout and a wider one. Give each a door and a route through the centre or alongside the beds. Mark the layouts in the garden and try moving through them with your usual tools. If one option feels awkward before plants are added, rearrange it on paper first. This can show whether you need extra width, extra length or a different door position.
Compare the usable height as well as the footprint
The ridge height tells you the highest point of the roof. Ask for the height near the side walls as well. That is where shelving, plant supports or a bench may go. If you want an upright work surface under a sloping roof, check that you can stand beside it without leaning forward. Draw the positions of tall crops on a side view so you can see where they will meet the roof.
Check how windows, braces and doors affect the space inside. A shelf that fits against an empty wall on a drawing may interfere with a brace or a window opener. Ask which points can support accessories on the model you are considering. Keep the position and maximum depth of shelving on the plan when requesting a quote.
Choose between a freestanding and a lean-to greenhouse
A freestanding aluminium greenhouse gives you a choice of orientation if the garden has room around the footprint. A lean-to can fit beside a suitable wall and may leave more of a small garden open. Inspect the wall for windows, pipes and roof overhangs. Confirm the attachment and foundation requirements with the supplier for the exact model before deciding that the space is suitable.
Compare access to all sides for cleaning and upkeep. Sketch where a hose will run and where water from the greenhouse roof will go. If the site sits close to a fence, check how you will reach the glazing and whether the installation team will have enough space to work.
Compare glazing, doors and ventilation as a package
Ask which glazing is included and what can be specified separately for the roof and sides. Consider the view, privacy and available growing light at your site. Then check the number and positions of vents and whether automatic openers are compatible. Think about when you can open the door and whether a lower opening is available to bring air in while warm air leaves through the roof.
Measure the door opening against the largest item you expect to move through it. If you use a wheelbarrow, check the handles and the space needed to turn. A clear path from the shed or kitchen can matter as much as the shape of the greenhouse itself.
Check exactly what is included in the quote
Put the frame dimensions, glazing, door arrangement, vents and optional accessories on one list. Ask which parts come with the greenhouse and which are priced separately. Confirm the base dimensions, delivery access and assembly requirements. Share a photo of the garden and your sketch so the supplier can check the configuration against the way you intend to use it.
For more detail on the main choices, see the glazing guide and our guide to choosing a greenhouse location.
Plan for the second growing season
Leave a spare bay or a removable bench if you expect your growing plans to change. In the first year, you might use the space for seed trays. Later, the same area could hold taller plants or a small seat. Ask which shelves or supports can be added after installation and where they attach. If you are buying on a tight footprint, compare the flexibility of each layout before committing to permanent beds.