Garden & Lawn

5 Best Aluminium Greenhouses

Last updated on June 3rd, 2021

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An aluminium greenhouse is a right solution if you’re looking for a lightweight outdoors growing room and want something more permanent than a pop-up greenhouse or larger than a mini greenhouse. We review the Best Aluminium Greenhouses in a wide range of sizes, identifying their pros and cons and discussing their features along with our recommendations. Our Buyer’s Guide tells you what you need to be familiar with when making your greenhouse buying decision.

BEST PICK

Outsunny 6ft x 6ft Polycarbonate Aluminium Frame Greenhouse
This square(ish) greenhouse (with a silver frame) is a good size for most domestic gardeners. It’s a walk-in structure with enough room on either side of the extra-wide door to put a bank of shelves for your plant pots and garden accessories. This aluminium structure is rust-proof and very low maintenance. The double-layered polycarbonate panels let in over 80% of the available sunlight while keeping out 100% of the UV rays. Your plants will thrive in this light. A roof window vent (plus the door of course) lets you control the airflow into the interior of the greenhouse and hence the temperature and the humidity. The Outsunny Polycarbonate Greenhouse is a sturdy and durable basic greenhouse that suits most gardeners’ growing needs.

Runner-up

Palram Mythos 6ft x 8ft Silver Greenhouse
The Palram Mythos 6ft x 8ft Silver Greenhouse is the next size up to our Best Pick greenhouse but that extra 1.12m2 of floor space lets you grow quite a few more tall or climbing plants or put in an extra bank of shelves. This is also an aluminium greenhouse but the base frame is made of sturdy and rust-resistant steel that adds to the stability of the structure. The TwinWall polycarbonate panels are 4mm thick and ridged, yet they’re still transparent enough to let in the sunlight and for you to see inside. The Palram Mythos comes in a variety of sizes all the way up to 185cm x 426cm.

Best 5 Aluminium Greenhouses reviews

1. Outsunny 6ft x 6ft Polycarbonate Aluminium Frame Greenhouse

BEST PICK

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Outsunny Clear Polycarbonate Greenhouse Aluminium Frame Large Walk-In Garden Plants Grow Galvanized Base 6 x 6ft

The Outsunny 6ft x 6ft Polycarbonate Aluminium Frame Greenhouse falls, in size, in between a greenhouse for “pottering around” and one for an enthusiastic gardener who starts all their own seedlings. This Outsunny model doesn’t quite have the headroom of other models but it does have a wide, lockable, door to wheel things through.

The polycarbonate panels are 4mm thick, double-layered and initially clear, though the ridging in them does cloud things a bit. But you can still see through them and plenty of sunlight (but not UV rays) reaches your plants. UV rays tend to make plastic discolour and become fragile enough to shatter. Some online reviewers report that you need to reinforce the panels in their frames with silicone caulk or something similar as they tend to fly out in windy times. This is a common complaint found with many polycarbonate greenhouses so you can look upon the internet what to do about it.

The traditional roof window vent lets you control the airflow and temperature inside the greenhouse to give your seedlings and plants the best possible start to their lives.

The built-in gutters running around the roof and the downspouts at the corners stop rain from running in sheets off the greenhouse and down the walls. Consider collecting this water and using it to water your plants.

Pros

  • Aluminium alloy frame walk-in greenhouse, powder-coated in silver-white with a single, lockable, wide door that opens outwards.
  • All panels are double-layered, 4mm clear, rigid polycarbonate.
  • Polycarbonate is UV-protected and waterproof.
  • Rain gutters are integrated all around the bottom of the slanted roof and have downspouts to drain off the collected water.
  • A single window in a slanted roof opens outwards to circulate fresh air inside the greenhouse.
  • Dimensions: 190cm (width); 182cm (depth and 195cm (height).

Cons

  • No floor included.
  • Panels don’t fit in securely.
  • Need help putting it together.

Our recommendation

The Outsunny Clear Polycarbonate Greenhouse is a square greenhouse that’s quite easy to organise inside with at least two banks of shelves. The door opening goes quite a way up into the roofline as this model is somewhat less tall than other units. The reinforced poles give stability to the structure as well as make the frame more long-lasting.

The Outsunny Greenhouse is our Best Pick of Aluminium Greenhouses. Its size suits most home gardens and we like its lockable door, just to keep your garden tools secure.


2. Palram Mythos 6ft x 8ft Silver Greenhouse

Runner-up

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Palram Mythos 6x8 ft Silver Greenhouse -TwinWall Polycarbonate, Aluminum Frame, Base Included

The Palram Mythos 6ft x 8ft Silver Greenhouse has the manufacturer’s usual high quality in its silver aluminium frame and TwinWall polycarbonate panels. Palram’s unique “Sliding Into” assembly method lets you slide the panels into their frames and the frames together. This method also increases the wind resistance of the structure (up to 90km/hr).

The frame is constructed of aluminium, all except for the base frame around the bottom which is made from alloy steel. The steel part serves to add structure to and strengthen the frame and hold all the aluminium posts in their place. It’s also highly durable and won’t rust.

The panels are the usual transparent polycarbonate with ridges in them, and in this model, it’s 4mm thick. The ridges serve to strengthen the panes and make them more rigid as well as to diffuse the sunlight. You can still see into the greenhouse through them and they let in over 80% of sunlight. All the polycarbonate panels are 100% protected from UV rays so they don’t become brittle and snap.

The built-in gutters channel any water on the roof to the downspouts at the corners. You can connect a pipe to these spouts to take the water wherever you want it instead of having it drip directly down. The single swing door is lockable to keep everything inside secure, though you do have to provide your own lock.

The Palram Mythos greenhouse comes in many different sizes starting at 185cm x 126cm and going up to 185cm x 426cm.

Pros

  • Silver powder-coated aluminium frame with a single door that opens outward.
  • TwinWall ridged polycarbonate panels have two walls and let in 82% of available light.
  • The base frame of the greenhouse is made of galvanised steel for durability.
  • Single window vent in roof opens outwards for ventilation.
  • Gutters around the roof collect rain and direct it through downspouts to the ground.
  • Palram’s slide-in assembly system makes putting this greenhouse together easier.
  • Five-year manufacturer’s warranty (limited).
  • Dimensions: 247cm (width); 185cm (depth) and 208cm (height).

Cons

  • No floor.
  • Poor assembly instructions.

Our recommendation

The Palram Mythos 6ft x 8ft Silver Greenhouse is large enough for the hobby domestic gardener. It allows you to put shelves on both sides of the single entrance and still have plenty of room to work. This aluminium and alloy steel greenhouse is built for durability and it’s practically maintenance-free.

We recommend the Palram Mythos 6ft x 8ft Silver Greenhouse for those who grow lots of vegetables and annuals from scratch. It’s the Runner-up choice in our review for its high quality and choice of sizes.


3. Palram 8ft x 8ft Glory Greenhouse

Best Premium Aluminium Greenhouse

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Palram 702400 8 x 8 ft Glory Greenhouse - Grey

The Palram 8ft x 8 ft Glory Greenhouse is the premium greenhouse in our review. It’s a top-of-the-line greenhouse not just for its size (and price) but for the high-quality features it has. The powder-coated aluminium frame is a very neutral grey colour that fades unobtrusively into the landscape of any garden.

This square greenhouse is the largest one we review. The rust-resistant structure has a steel base frame (also rust-resistant) that adds structural support to the greenhouse, keeps the frame in true alignment and gives stability to the whole unit. Alas, there’s no floor with your purchase so you’re responsible for providing a flat surface for this model to stand on.

The panels, as is usual, are made of twin-walled clear polycarbonate that has been ridged. But in the Palram greenhouse, the thickness of the plastic is 10mm rather than the usual 4mm. This gives much better insulation and strength to the structure and you can still see through it to your plants inside the greenhouse.

Tall people can stand up without any trouble inside this greenhouse as there’s extra headroom for them and for growing really enthusiastic climbing plants. The single swing door is also extra wide for you to wheel in some of your garden equipment, wheelbarrows and so on, and for inclusive access for wheelchairs.

This Palram model has the usual window vent in the roof for ventilation, but with an important upgrade. This vent comes with an automatic vent opener that opens the window when it’s warm outside and closes it when the weather cools off. That’s one less garden task for you to remember to do. If the window is too large for the air circulation you need, use the louvre window that’s at the bottom of one of the side walls.

Pros

  • Grey powder-coated walk-in greenhouse with an extruded aluminium frame.
  • Sturdy, rust-resistant, extra-thick extruded aluminium profiles for long-lasting durability
  • Heavy-duty 10mm extra thick polycarbonate ridged walls (UV-protected) for extra strength and durability.
  • Has galvanised steel floor base and four legs to raise the greenhouse floor (not included) above the ground.
  • Extra high headroom for tall people and climbing plants.
  • Panels slide into each other for easy assembly.
  • The single door, wide width, is hinged and lockable and opens outwards.
  • The single roof vent opens outwards and has an automatic vent opener.
  • The side louvre also helps with air circulation and ventilation.
  • Gutters and downspouts drain and clear away any water on the slanted roof.
  • Comes with plant hangers.
  • The manufacturer’s warranty is for 10 years.
  • Dimensions: 244cm (width and depth) and 268cm (height).

Cons

  • No floor.

Our recommendation

The Palram 8ft x 8ft Glory Greenhouse has all the premium features that a large greenhouse needs to maintain the interior environment in the best interests of your plants. The extra high headroom lets you grow tall plants and the two methods of ventilation (roof window vent and side louvre) enable you to closely control the inside growing climate.

We recommend the Palram 702400 8ft x 8ft Glory Greenhouse for those gardeners who expend a lot of time, effort and space in growing their plants from scratch and over-wintering their successes.


4. Outsunny 6ft x 4ft Clear Polycarbonate Greenhouse

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Outsunny Clear Polycarbonate Greenhouse Large Walk-In Green House Garden Plants Grow Galvanized Base Aluminium Frame w/Slide Door (6ft x 4ft)

The Outsunny 6ft x 4ft Clear Polycarbonate Greenhouse has an attractive dark green powder-coated aluminium alloy frame. With its double-layered panels made of 4mm polycarbonate, this greenhouse withstands winds up to 12m/s despite it being lightweight. Metal cross beams from the corner posts add to the stability of the structure.

The polycarbonate walls are of clear plastic but this is ridged to diffuse the sunlight, giving them a semi-opaque look. However, plenty of sunlight still reaches the plants inside and you can look in and see what’s happening there. The polycarbonate is UV-protected to keep out 100% of UV rays which tend to make the plastic brittle and discoloured. Online reviewers state that the panels are not very rigid and need to be further fixed in the frame, perhaps by silicone gel or even duct tape.

This Outsunny greenhouse is one of only two models in our review to have a sliding door. This lets you put the greenhouse in a narrow space where there isn’t enough room to open a regular swing door outwards. The window vent on the roof opens an adjustable amount to let fresh air circulate to provide ventilation and to create the growing environment that’s best for your plants.

The roof also has an integral rain gutter that collects any rainwater and directs it into the downspouts at the corners. This avoids having rain run off the entire roof in sheets. The four spots on the ground at the corners of the greenhouse will be well irrigated,

Be aware that this greenhouse does not come with a floor – whatever surface you stand it on is what you walk on inside the structure.

Pros

  • Dark green powder-coated aluminium alloy frame greenhouse with single sliding door.
  • Walls constructed from UV-resistant ridged transparent polycarbonate sheets that allow natural light to shine through.
  • Structure supported by cross beams on the corners.
  • The window on the roof opens outwards for air circulation and ventilation.
  • Rain gutter and outlet collect and drain water.
  • Dimensions: 190cm (width); 132cm (depth); and 201cm (height).
  • Floor area: 2.51m2.

Cons

  • Floor is not included.
  • Polycarbonate sheets not rigid.

Our recommendation

The Outsunny Clear Polycarbonate Greenhouse Large Walk-In Green House  (6ft x 4ft) is a manageable size for most gardeners. It’s dark green colour is visually attractive and fits in with any garden landscape. You have the window vent for ventilation and the sliding door is a space saver.

We recommend the Outsunny Clear Polycarbonate Greenhouse Large Walk-In Green House (6ft x 4ft) if you’re looking for a small permanent aluminium greenhouse.


5. Palram 4ft x 2ft Lean-to Grow House

Best Compact Aluminium Greenhouse

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Palram 4x2 Lean-to Grow House

If you want an aluminium greenhouse but only have a 1.21m bare patch of outside wall with 60cm ground clearance, the Palram 4×2 Lean-to Grow House is for you. This lean-to greenhouse has three sides of polycarbonate panels and uses your home/garage/shed/fence wall as the back side of the structure.

The polycarbonate panels are the usual twin-walled 4mm thick panels that are transparent but ridged/frosted. The panels on this model let in over 80% of the good sunlight and keep out 100% of UV rays so your plants thrive in their environment and the panels don’t become brittle and shatter.

The sliding door on the front of the greenhouse is almost one half of the wall’s width. It opens smoothly so you can tend to your growing items. Some online reviewers report that you do have to lean in a bit to reach the plants furthest from the door but that’s not too much of a hassle. The sliding door lets you have a smaller clearance in front of the greenhouse than with a swing door.

The entire roof is hinged and forms the air vent. Lift it up to any one of a number of positions to control how much air circulates within to reduce the internal temperature. Despite being steeply sloped, the roof is sturdy and stands up to a snow load of 80kg/m2. The whole structure itself resists winds up to 90km/hr.

 Pros

  • Aluminium frame lean-to greenhouse with a very compact footprint for small spaces.
  • Fits up against a house, garage or garden wall.
  • Transparent and ridged polycarbonate panels (twin wall) are protected from UV rays and let through 90% of light.
  • The entire roof is hinged and opens as a vent to let fresh air circulate inside.
  • A single sliding door is half the width of the greenhouse.
  • The base frame is constructed of galvanised steel to be strong and rustproof.
  • Gutters and downspouts catch the water running off the slanted roof.
  • Dimensions: 125cm (width); 63cm (depth) and 160cm (height – highest point).

Cons

  • Difficult to assemble and poor instructions.
  • No floor.

Our recommendation

The Palram 4×2 Lean-to Grow House proves that there’s no reason people with balconies or small gardens should go without permanent greenhouses. Despite its small footprint, this lean-to greenhouse offers 1.0m3 of growing space, including the headroom to growing tall and climbing plants.

We recommend the Palram 4×2 Lean-to Grow House for anyone with a small outdoors area who’s always dreamed of having a permanent greenhouse.


Buyer’s Guide

Our Buyer’s guide identifies the things you should know about as you head out to select your ideal aluminium greenhouse.

Aluminium – pros and cons

The aluminium frames of the greenhouses we review make them lightweight. Once the metal has been powder-coated it’s completely rust- and weatherproof as well as long-lasting. These features are both pluses and minuses for the greenhouses.

A lightweight greenhouse is generally fairly easy to assemble, though some online reviewers may argue this. However, the frame may feel flimsy and be bent quite easily. In addition, if the polycarbonate panels are not very rigid, the whole structure may feel and act unstable, especially in times of high winds.

Aluminium doesn’t rust so even if the powder coating wears off the exposed metal will be alright.

Panels

All the panels in our review greenhouses are made of double-layer polycarbonate with UV protection. The protective coating stops the UV rays from making the plastic brittle and so shatter or discolour. The differences lie in the thickness of the polycarbonate (the thicker ones offer greater insulation) and their transparency which affects how much light is let in and how much you can see into the greenhouse from the outside. Most are ridged/frosted to diffuse the direct sunlight.

A common complaint about most polycarbonate greenhouses is that the panels seem a little insecure in their frame. Online reviewers recommend that you use silicon caulking to hold them in place, or even duct tape them in.

What to look for when choosing an aluminium greenhouse

Base vs floor

Base vs floor is terminology that you need to understand with respect to a greenhouse as it’s confusing. “Base” refers to the bottom of the greenhouse frame, the bit that actually stands on the ground. In the best aluminium greenhouses, this is usually made of galvanised steel to make it rust-proof, waterproof and strong. The base may be about 15cm to 20cm high and this lets you lay a floor above ground level.

All greenhouses should have a base but only a few come with a floor which is the actual surface you walk on. Most greenhouse interiors are open inside and the floor is whatever surface you place them on. You can make your own (level) surface from concrete or cement slabs, perhaps a wooden deck or even your lawn. The more level the ground surface, the more evenly your greenhouse will sit.

Measurements

Measuring your area to work out what size aluminium greenhouse to buy

As with most garden products we review, we see many online complaints that the item is smaller than people expected. Carefully check the measurements given (keeping in mind that some of them may be wrong or mistyped) and then outline them with string on your garden. Stand inside the outline and imagine how many plants you can get in there and how you’ll move around.

Be aware that the height measurement given usually refers to the height at the tip of the roof and not to the overall standing height, which is usually quite a bit shorter.

Gutters and downspouts

Many greenhouses come with gutters and downspouts to collect any rain or thawed snow from the roof and direct it towards the ground. Check whether you have the option of attaching a down pipe to the downspout so all that water doesn’t just splash down 2m to the ground. You could perhaps collect the water and reuse it for watering your plants.

Door and window vent

Best Greenhouse Reviews -Buyers Guide and our Top 6 Picks including wood and steel greenhouses

Most aluminium frame greenhouses have a single door, usually a regular swing door that opens outwards. Check whether this is a wider than usual door if you want to wheel some of your garden equipment or a wheelchair inside the greenhouse. Additionally, check that doors are lockable to keep your plants and garden tools inside more secure.

One online reviewer interestingly commented that she couldn’t close the greenhouse door when she was inside – there was no handle there. We appreciate that this may be a safety feature so children can’t lock themselves in, but leaving the door open all the time you’re pottering around inside the greenhouse wrecks the optimum growing environment you’ve carefully built up in there.

And also check whether the window vent (if there is one) in the roof can be securely and completely closed as well as opened to different positions. Some online reviews complain that either the window doesn’t close completely or that the closing latch doesn’t hold it tight. Either way, this can enable condensation to build up in your greenhouse, once again negatively affecting your growing environment.


Final Conclusion

Aluminium frame greenhouses offer a lightweight sturdy structure in the same size ranges as steel greenhouses. The ones in our review all have polycarbonate panels which provide better insulation and more strength than glass. Your biggest decision with these greenhouses is making sure that you buy the right size for you and your plants to grow into.

Our Best Pick is the Outsunny Clear Polycarbonate Greenhouse Aluminium Frame Large 6ft x 6ft. This size of greenhouse suits most domestic gardens and gardeners, and this is a sturdy model.

Our Runner-up is the Palram Mythos 6ft x 8ft Silver Greenhouse. This greenhouse has a unique “Sliding Into” assembly method and design that makes it extremely wind resistant.

The Palram 702400 8ft x 8ft Glory Greenhouse is our Best Premium Greenhouse. This model has the top-of-the-line features that are necessary to maintain the best environment for your plants in this large a space.

Now you have your aluminium greenhouse, you need to organise it efficiently, and our Best Greenhouse Staging and Shelving Products to Organise Your Greenhouse helps you with that.

If you plan on using your greenhouse over the winter, check out the advice in our How to heat a greenhouse and everything you need to consider article.


Last update on 2021-06-19 / Affiliate links / Images from Amazon Product Advertising API

Welcome to my site, my name is John and I have been lucky enough to work in horticultural nurseries for over 15 years in the UK. As the founder and editor as well as researcher, I have a City & Guilds Horticultural Qualifications which I proudly display on our About us page. I now work full time on this website where I review the very best gardening products and tools and write reliable gardening guides. Behind this site is an actual real person who has worked and has experience with the types of products we review as well as years of knowledge on the topics we cover from actual experience. You can reach out to me at john@pyracantha.co.uk

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