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Cold frame buying guide

Updated: October 2026

You are looking at timber kits on amazon.co.uk that use cold frame and greenhouse in the same title, and you need a footprint that will actually take your seed trays. This cold frame buying guide sorts shape, glazing and timber care before you compare individual rows. The [cold frame comparison](/hub/raised-beds-greenhouses-and-compost/cold-frame) lists six listings captured on 20 October 2026, priced from £46.99 to £129.99. Peter F. used those amazon.co.uk pages and public Royal Horticultural Society guidance. This is not a lab frost test. A qualifying purchase can earn a commission at no extra cost to you.

You are looking at timber kits on amazon.co.uk that use cold frame and greenhouse in the same title, and you need a footprint that will actually take your seed trays.

Our top picks

Outsunny Outsunny fir cold frame

Best overall

Outsunny Outsunny fir cold frame
8.6/10about £46.99
View offer
SG Traders SG Traders wooden greenhouse

Rank 2

SG Traders SG Traders wooden greenhouse
8.4/10about £79.99
View offer
Outsunny Outsunny twin-lid cold frame

Best value

Outsunny Outsunny twin-lid cold frame
8.0/10about £47.59
View offer
On this page
  1. 1.Footprint and height before the brand
  2. 2.Glazing and timber care
  3. 3.What the lid and the star line can tell you
  4. 4.Shelf prices and a last check

Footprint and height before the brand

The RHS describes a typical cold frame depth of about 45–60 cm: a box you reach into from above, not a house you walk into. In this capture the low Outsunny single-lid frame is 100 × 65 × 40 cm, and the twin-lid Outsunny is 100 × 50 × 36 cm. The Spear & Jackson COLDFRAME1 does not give you one number. The technical row says 90 × 45 × 46 cm, while a title bullet says 1000 × 660 × 400 mm. The SG Traders unit is about 69 × 49 × 120 cm with shelves in the title, and the Outsunny three-tier is 58 × 44 × 78 cm. If you cannot bend to a low lid, the cabinet is the shape that matches how you work.

Glazing and timber care

Every kit here uses plastic glazing. Polycarbonate is named on the Outsunny and SG Traders cover rows. The Spear & Jackson cover row says plastic panes, and the frame row says plastic, even where the marketing talks about timber. The feel good cover row names polyvinyl chloride. None of the six claims toughened horticultural glass. The RHS describes polycarbonate as cheaper and longer-lasting than glass, with less light passing through. UK reviews on the fir Outsunny ASINs repeat a coat before winter. Spear & Jackson reviews add soft wood and annual treatment. Specialist aluminium and glass often starts above £200.
Outsunny Outsunny fir cold frame

Testsieger

Outsunny Outsunny fir cold frame
8.6/10about £46.99
View offer

What the lid and the star line can tell you

A lid you can prop is part of the purchase. The RHS says you should open a cold frame on warm days, peg a lightweight frame in wind, and treat bubble plastic inside as something that cuts light and still needs airflow if you want to limit mould. The twin-lid Outsunny lists two top covers, so one side can stay cracked while the other stays shut. Spear & Jackson reviews say the lid props are stiff and sit on the outside compared with the photo, and that paint on the metal props blisters. The three-tier Outsunny, 3.2 from 201 reviews at £56.99, is the blunt warning: many UK reviews say the doors do not meet. Stars show what recent buyers repeated, not five winters on wet soil. Daily airflow is on cold frame ventilation.

Shelf prices and a last check

The prices are shelf figures on 20 October 2026, not a census of every cold frame on amazon.co.uk. About £47 to £69 covers the two low Outsunny frames, the three-tier at £56.99, and the Spear & Jackson at £68.94. The SG Traders cabinet is £79.99 and the feel good frame is £129.99. Paying more inside this list buys a different shape or a heavier pack, not a tested frost temperature. If goods are not of satisfactory quality, the Consumer Rights Act 2015 section 22 gives you 30 days to reject them. Write the centimetres down before checkout.

Common questions

What size cold frame do I need for two seed trays?
A length around 100 cm is the practical size in this capture for two trays side by side. The low Outsunny is 100 × 65 × 40 cm, and the twin-lid version is 100 × 50 × 36 cm, so the second is narrower. The RHS cites a typical depth of about 45–60 cm, so both lids sit a little low for tall pots. Do not use the Spear & Jackson millimetre bullet and the 90 × 45 × 46 cm row as one footprint.
Should I treat fir wood before winter?
UK reviews on the fir Outsunny listings repeat a coat before winter, and Spear & Jackson reviews talk about soft wood that wants treatment each year. The feel good reviews mention pretreatment as well. Damp soil at the base rots untreated timber faster than a dry patio. A coat is ordinary maintenance for these kits, not a sign that the listing promised tanalised hardwood. None of the six is a brick-sided permanent frame.
Is a cold frame or a mini greenhouse better on a balcony?
A low frame of about 40 cm needs floor space and a lid you can lift without standing inside it. A 120 cm cabinet, such as the SG Traders unit at 69 × 49 cm on the ground, needs headroom and a clear path to the doors, which many balconies do not have. The RHS says lightweight frames should be pegged down, which many balconies will not allow.
Is the Spear & Jackson worth more than the Outsunny?
In this capture the Spear & Jackson is £68.94 with 4.0 from 172 reviews, and the low Outsunny is £46.99 with 4.3 from 271. You pay about £22 more for the brand and you still have to reconcile 90 × 45 × 46 cm with a 1000 × 660 × 400 mm bullet. Reviews praise easy assembly and then criticise soft wood, stiff outside props and blistered paint.
Will polycarbonate protect plants from frost?
These unheated boxes moderate temperature. They are not a guarantee against a hard frost, and none of the listings publishes a frost rating in degrees. The RHS treats a cold frame as better frost shelter than a cloche when you ventilate properly, and still expects fleece or a delay in planting when a severe frost is forecast. Shutting the lid on a sunny day can overheat plants.
Can the frame sit on paving?
Yes. The RHS describes cold frames on soil, gravel or paving, used for hardening off and a short season extension. Paving avoids the wet-soil rot that untreated timber suffers, though you still need to level the base so the lid sits down. Pegs are harder on slabs, so use weights if the site is windy. The frame only shelters what you put inside it.

Related pages

Best cold frame

Cold frame vs mini greenhouse

How to use a cold frame

Cold frame

Cold frame ventilation on warm days and frosty nights

Sources

Public UK sources from the research digest, last checked on 20 October 2026. Amazon.co.uk listing lines are the price and review source for the six ASINs. No frost or assembly test was run.

  1. RHS — Coldframes and mini-greenhouses (retrieved 20.10.2026)
  2. RHS — Choosing greenhouses (retrieved 20.10.2026)
  3. RHS — Hardening off tender plants (retrieved 20.10.2026)
  4. RHS — Cloches (retrieved 20.10.2026)
  5. RHS — Frost damage prevention (retrieved 20.10.2026)
  6. Gardeners' World — Best cold frames 2025 (retrieved 20.10.2026)
  7. Consumer Rights Act 2015, section 22 (retrieved 20.10.2026)
  8. GOV.UK — Returns and refunds (retrieved 20.10.2026)