About Our Cold Frames
A cold frame is essentially a miniature greenhouse without heating—a transparent box that traps solar warmth to extend your growing season by 6-8 weeks at both ends. Unlike mini greenhouses, cold frames sit directly on the ground, creating a protected microclimate perfect for hardening off seedlings, growing winter salads, and protecting tender plants from frost.
Why We Chose This Range
“We curating our Cold Frame collection based on 'Structural Stability'. The most common mistake is buying lightweight plastic units that blow away in the first spring gale. We chose the Elite and Swallow ranges because they use the same high-tensile aluminium and 3mm toughened glass as full-scale greenhouses. We prioritised models with floor-fastening brackets specifically because a cold frame acts like a wing in high winds; our selection ensures your investment stays exactly where you built it, protecting your seedlings through every UK storm.”
— Matt, Founder of Greenhouse StoresOur collection features premium Access cold frames and Elite cold frames built with rust-proof aluminium frames and your choice of toughened glass or twin-wall polycarbonate glazing. Every model includes sliding roof windows for ventilation control, built-in gutters for rainwater management, and removable staging shelves. Prices start from £249, and all cold frames come with free UK delivery and warranties ranging from 10 to 25 years.
The difference between a £200 wooden cold frame and our aluminium models? You'll still be using ours in 2050.
🔧 Matt's Installation Tip: The "Thermal Mass" Strategy
Cold frames are small, which means they lose heat quickly overnight. To maximise performance, I always recommend placing the frame on a bed of 50mm dark paving slabs or a layer of slate chippings rather than directly on soil. This acts as a 'thermal battery'—absorbing solar heat during the day and radiating it back to your pots as the temperature drops at 3:00 AM.
Crucially, ensure you have a perfectly level foundation. Even a 5mm twist in the base will cause the roof vents to misalign, creating gaps that allow frost to creep in. If you are placing your cold frame against a south-facing house wall, you can effectively increase its thermal performance by another 20% by utilising the wall's radiant heat. Read our full base preparation guide here.
Why Aluminium Frames Beat Wood and Plastic
Most cold frames on Amazon and at garden centres use wooden or plastic frames. Wood rots within 3-5 years, and plastic frames crack in UV light. Aluminium frames solve both issues permanently.
Technical Comparison: Material Efficiency
| Feature | Aluminium Cold Frames | Timber Cold Frames |
|---|---|---|
| Material | Extruded Aluminium | Pressure-Treated Red Cedar/Pine |
| Maintenance | Zero (Wipe Clean) | Occasional Oil/Stain |
| Insulation | Moderate | High (Natural Thermal Break) |
| Glazing | 3mm Toughened Glass | 3mm Toughened Glass |
| Lifespan | 25+ Years | 15-20 Years |
📏 Cold Frame Sizing Reference
2x4 Model: 12-16 seed trays.
4x4 Model: 30-35 seed trays (UK's most popular).
4x8 Model: 70+ seed trays (Professional capacity).
Frequently Asked Questions
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What is the difference between a cold frame and a mini greenhouse?
A cold frame is typically a low-profile structure used on the ground for hardening off seedlings and protecting low-growing crops. A mini greenhouse is usually taller and features shelving, making it better for vertical growing on patios or balconies where space is at a premium.
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Is glass or polycarbonate better for a cold frame?
3mm toughened glass is superior for light transmission and weight, which helps the frame stay stationary in wind. However, polycarbonate offers better insulation (u-value) and is virtually unbreakable, making it ideal for gardens with children or pets.
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How do I prevent my plants from "cooking" in a cold frame?
Ventilation is vital. On sunny spring days, temperatures inside a closed cold frame can spike to 35°C+. You must open the roof vents at least 10-15cm every morning. For ultimate protection, we recommend fitting an automatic vent opener to manage the climate while you are at work.
✅ Ready to Extend Your Growing Season?
Browse our complete range of cold frames above, from compact 2x4 models to 8x4 professional frames. Every cold frame includes free UK mainland delivery. For help choosing size or glazing, call our specialists on 0800 098 8877.