Put the brands you are actually considering side by side

Best fit

Buyers who want a hand-built glasshouse to keep for 20-plus years and are willing to pay for it.

What it does well

• British maker founded in 1938 with an 85 year track record of hand-built aluminium glasshouses
• The only aluminium greenhouses endorsed by the Royal Horticultural Society (RHS)
• Heavy, hand-made aluminium framing, built and installed by the company's own fitters

Check before you order

• Most models sit on a dwarf wall, so budget and plan masonry foundation work before delivery
• Confirm the guarantee in writing. The 30 year structural cover is non-transferable and the 10 year paint cover applies only to the original purchaser
• Lead times run around 13 weeks or longer from order confirmation, and some buyers report the full request-to-install cycle closer to a year, so order well ahead of your season

Warranty reality

Hartley markets a 30 year structural guarantee it calls a Lifetime Guarantee, covering the structure and installation, with a separate 10 year paint guarantee that applies only to the original purchaser. The guarantee is explicitly non-transferable, and Hartley notes that certain components carry shorter terms or fall outside the guarantee entirely, so ask for the full guarantee table in writing.

Best fit

Buyers who want real tempered glass and a Victorian look without a five-figure top-tier price.

What it does well

• Real 4mm tempered (safety) glass, thicker than the 3mm many kit greenhouses use
• Sturdy aluminium profiles with stainless steel hardware and an included 6 inch aluminium foundation frame
• Strong structural ratings, with the VI34 rated to around 120 mph wind and 25 PSF snow load

Check before you order

• Confirm the 18-wheeler can reach your property and arrange help for offloading a heavy palletized shipment
• The 6 inch aluminium base frame is included, but you still need a level, prepared foundation such as gravel, pavers, or a concrete pad under it
• Inspect every glass panel on delivery and document any breakage immediately for the freight and warranty claim, and anchor properly for local wind and snow loads

Warranty reality

Exaco, the exclusive US distributor, publishes the warranty for Janssens glass greenhouses: up to 15 years on the aluminum frame and stainless steel hardware, and up to 10 years on defects in materials and workmanship when assembled to the manufacturer's instructions. Tempered glass glazing is excluded (replacement panes available at reasonable cost), as are operating parts like window-opener pistons and damage from extreme weather or unshoveled snow load.

Best fit

DIY buyers who want twin-wall polycarbonate that lasts on a real base without a premium price.

What it does well

• Affordable and widely available off the shelf at big-box retailers and Amazon, often discounted
• Rust-proof aluminum frame and shatter-resistant, UV-protected polycarbonate rather than breakable glass
• DIY-friendly, especially the Snap & Grow SmartLock system that needs few or no screws

Check before you order

• Anchor the greenhouse firmly to a level foundation immediately after assembly, since wind and panel blow-out are the most common failure mode
• If insulation or snow load matters, step up to twin-wall models (Mythos or Glory 4-10mm) rather than the thin single-wall entry kits
• Plan on two people and the better part of a day to build, and check the specific model's snow and wind rating against your climate

Warranty reality

Palram/Canopia states that all its greenhouses carry a warranty of at least 5 years, with some models covered longer; the Harmony, Mythos and Hybrid ranges advertise a 5-year warranty on frames and panels. Because units are bought through third-party retailers (Home Depot, Lowe's, Costco, Amazon), claims and returns are typically handled through the retailer and Canopia's own support, so keep proof of purchase.