Step 5 - Greenhouses
Greenhouse Kit vs DIY Build
Building your own is cheaper on materials and expensive in time. The glazing is where the argument is actually settled.
Janet H. - the hands-on owner behind Janet Media Group.
Published - last updated
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Buy a kit if you want a standard-sized greenhouse quickly. Build if you want a non-standard size, want to use a wall of the house, or already have most of the materials. The reason the choice usually falls to a kit is glazing: buying polycarbonate sheet at retail quantities is expensive, and it is the largest cost in either route.
| Kit | DIY build | |
|---|---|---|
| Time | A day with two people | Several weekends |
| Material cost | Fixed and known | Lower on frame, similar or higher on glazing |
| Sizes | Standard footprints only | Anything you want |
| Skill needed | Following a manual | Real carpentry and accurate measuring |
| Spares | From the manufacturer | Whatever you can source |
| Lean-to against a wall | Limited options | Straightforward, and thermally efficient |
| Resale or relocation | Dismantles and moves | Usually stays |
Quick picks
| # | Product | Best for | Score | Price |
|---|---|---|---|---|
| 1 |  Top pickPalram Canopia Mythos GreenhouseAluminum frame, 4 mm twin-wall polycarbonate | A first real greenhouse | 9.0 | Check price on Amazon |
| 2 |  Palram Canopia Glory Greenhouse10 mm twin-wall polycarbonate throughout | Cold climates and winter growing | 8.9 | Check price on Amazon |
| 3 |  Quictent Portable Walk-In GreenhouseSteel tube frame with reinforced PE cover | The cheapest usable start | 7.8 | Check price on Amazon |
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Scores are our own editorial judgment, formed from published specifications and independent sources. They are not aggregated customer ratings, and they are not the result of hands-on testing, which we do not currently do. See how we choose.
Why glazing decides it
Twin-wall polycarbonate bought as individual sheets at retail is expensive, and the manufacturers of kits buy it at a scale you cannot. Once you price the glazing for a self-build, the saving over a comparable kit is usually far smaller than people expect -- and sometimes reverses.
Salvaged glazing changes that completely. Old windows, greenhouse panels from a dismantled structure, or offcuts from a commercial job make a DIY build genuinely cheap. If you have a source, build. If you are buying new sheet, do the arithmetic before committing.
Where DIY genuinely wins
- Lean-to against a south-facing wall. The wall provides structure, shelter and thermal mass, and kits for this are limited. It is also the most thermally efficient small greenhouse you can build.
- Awkward sites. A long narrow strip, a sloping plot, a corner -- kits come in standard footprints and your yard may not.
- Salvaged materials. Old windows, reclaimed timber, secondhand panels. This is where the real savings are.
- Heavier construction. If you want something built to last decades in a demanding climate, a well-built timber-framed structure beats a light aluminum kit.
Watch out for
- Old painted windows. Pre-1978 paint may contain lead. Test or avoid, particularly around food growing.
- Underestimating ventilation. A self-build needs vents designed in from the start, not added later. Extension guidance treats ventilation as core to the design.
- Racking. A timber frame that is not braced diagonally will lean over time and the glazing will not sit properly.
- Condensation and rot. Timber in a permanently humid structure needs to be able to dry. Detail it so water runs off rather than sits.
If the appeal of DIY is mainly cost, compare it honestly against a budget kit plus modifications, which is the same trade of money for weekends.
The picks in full
Top pick
Palram Canopia Mythos Greenhouse
Palram Canopia
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The sensible first greenhouse: an aluminum frame with twin-wall panels, sized to fit a normal backyard rather than a nursery.
Twin-wall polycarbonate is the thing that separates a greenhouse from a plastic tent. Two skins with an air gap between them insulate, and the panel diffuses light rather than throwing hard shadows, which suits seedlings better than clear glass does.
The Mythos sits at the point in the range where you get a proper aluminum frame, a roof vent and a lockable door without paying for the heavy-duty glazing. For starting seeds, hardening off, and stretching the tomato season at both ends, that is the right specification.
Two warnings from the manual that people ignore. Anchor it -- every lightweight greenhouse that ends up in a neighbor's yard was not anchored. And build it with a second person; the panels flex and the frame is not square until the last bolt.
What works
- Twin-wall panels diffuse light and insulate better than single-skin plastic
- Aluminum frame will not rust or need painting
- Lengths let you match the run to the space you have
- Roof vent included rather than sold as an extra
What does not
- 4 mm glazing is thin for real winter use
- Assembly is a long afternoon and genuinely needs two people
- Must be anchored -- an unanchored kit is a sail
Skip it if: you live somewhere with heavy snow load. 4 mm panels are a three-season specification; the thicker-glazed models exist for a reason.
| Frame | Rust-resistant aluminum |
|---|---|
| Glazing | 4 mm twin-wall polycarbonate |
| Sizes | 6 ft wide, several lengths including 6 x 8 and 6 x 10 |
| Ventilation | Roof vent, lockable door handle |
| Base | Integrated base rail, anchoring required |
Cold climates and winter growing
Palram Canopia Glory Greenhouse
Palram Canopia
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The heavy-glazed model in the range, and the one to buy if the plan is to keep growing through a real winter.
Glazing thickness is the whole argument for this kit. A 10 mm twin-wall panel holds substantially more heat overnight than a 4 mm one, and overnight is when a winter greenhouse either works or does not.
It is also the model to look at if you get real snow. Thin panels and light frames are a three-season specification; if you are in the Cascades or anywhere with a genuine snow load, buy the heavier structure rather than hoping.
None of that makes it heated. A greenhouse without a heat source holds a few degrees over outside, which is the difference between hardy greens surviving and not -- it is not a tropical house in January.
What works
- 10 mm glazing holds heat far better than 4 mm
- Rated for harder weather than the lighter kits
- Wider footprint gives room for benches down both sides
- Better vent provision as standard
What does not
- Substantially more expensive
- Thicker panels cut light transmission a little
- Heavy enough that assembly is a two-person, whole-day job
Skip it if: you only want a spring seed-starting space. You are paying a large premium for insulation you will use for three months of the year.
| Frame | Heavy-gauge aluminum |
|---|---|
| Glazing | 10 mm twin-wall polycarbonate |
| Sizes | 8 ft wide, several lengths |
| Ventilation | Roof vents, and a screened side vent on some models |
| Base | Integrated base, anchoring required |
The cheapest usable start
Quictent Portable Walk-In Greenhouse
Quictent
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A tunnel, not a building -- but the cheapest way to find out whether you will actually use a greenhouse before spending real money.
This is the honest entry point. A lot of people buy a greenhouse and discover they do not have the habit to use one, and finding that out cheaply is worth something.
It does real work in spring: hardening off seedlings, protecting young plants from a late frost, and giving you somewhere dry to pot up. Those are the jobs a first greenhouse actually does.
Treat the cover as a consumable and stake it properly. Every bad review of a tunnel greenhouse is a wind story, and almost all of them start with skipped guy ropes.
What works
- A fraction of the cost of a rigid kit
- Goes up in an hour with no special tools
- Packs away out of season
- Mesh windows give usable ventilation
What does not
- The cover degrades in UV and is a replaceable part
- Poor in wind unless properly staked and guyed
- Not a snow-load structure
Skip it if: you are in a windy or snowy spot. A covered frame is not a structure, and covers are a consumable.
| Frame | Powder-coated steel tube |
|---|---|
| Cover | Reinforced PE with mesh windows |
| Sizes | Several walk-in footprints |
| Ventilation | Roll-up door and mesh side windows |
| Anchoring | Ground stakes and guy ropes supplied |
Common questions
Is it cheaper to build your own greenhouse?
On the frame, usually. On the glazing, rarely -- twin-wall polycarbonate bought as retail sheets is expensive and it is the largest cost either way. Salvaged glazing changes the arithmetic completely; buying new sheet often brings a self-build level with a kit.
What is the best DIY greenhouse design for a home garden?
A lean-to against a south-facing wall. The wall supplies structure, shelter and thermal mass, it is the most thermally efficient small design, and kits for this configuration are limited -- so it is the case where building genuinely beats buying.
Can you build a greenhouse from old windows?
Yes, and it is where self-builds save real money. Check for lead paint on anything pre-1978, brace the frame diagonally so it cannot rack, design ventilation in from the start, and detail the timber so water runs off rather than sitting in joints.
How long does it take to build a greenhouse yourself?
Several weekends for a competent builder working from a plan, against roughly a day for a kit with two people. That time difference is the real cost of DIY, and it is why most people who value the growing season more than the building buy a kit.
Sources
Factual claims on this page are backed by the published sources below, and product specifications are the manufacturers’ own. Where a figure is not published, we say so rather than estimating it.