Low tunnel and small walk-in tunnel, step by step

1. Four small solutions

From fleece on a bed to a tunnel you walk into upright.

1. Fleece on the bed — Laid straight on the plants, per bed. For light frost, against insects and for an earlier harvest; lasts 2–4 seasons.
2. Low tunnel — 1–1.2 m wide, 50–60 cm high. For lettuce, radish, carrots and early peppers.
3. Mid tunnel — 1.5–2 m wide, 80–120 cm high. Tomatoes and peppers until June, strawberries.
4. Small walk-in tunnel — From 3 × 4 to 3 × 8 m, 2 m high, you walk in upright. Seedlings, 10–20 tomatoes, winter salad.

Why: A bed under a low tunnel thaws and warms up two or three weeks before the rest of the garden. Lettuce and radishes are picked in April, and peppers go in without fear of the last frost. A small walk-in tunnel is the next step: seedlings, tomatoes and winter salad.

• Many gardeners have both: fleece for frosty nights and a film tunnel for early spring.
• Large permanent tunnels are covered in module H11-03 A permanent polytunnel.

2. Materials

Hoops, a cover and whatever holds them to the ground.

1. Hoops for a low tunnel — Galvanised 5–6 mm wire is cheap and strong. Fibreglass rods 5–8 mm are light and don't rust, but they splinter when they break, so wear gloves.
2. Water pipe, not conduit — For the small walk-in tunnel, 32 mm plastic water pipe (MDPE/HDPE, PN 10): it bends without tools. Electrical PVC conduit goes brittle in the sun and cracks in frost.
3. Film or fleece — UV film 80–120 µm for tunnels, 150–200 µm for the walk-in tunnel. Fleece of 23–30 g/m² on hoops protects against frost to about −3 °C (27 °F).
4. What holds it down — Bury the edge 20–25 cm deep or weight it with sandbags every 1–1.5 m. String in a zigzag keeps the film in place in the wind; hoop clips alone won't hold in a strong wind.

Why: Hoops last for years, film for one season or a few. So the hoop must not tear the film, and the film must be UV stabilised. Builders' polythene without UV stabilisation is a rag within one summer.

• Fleece lets water and air through, so it doesn't overheat, but it warms less than film.
• Cap the ends of wire, rebar and stakes with caps or slit hose: they tear the film and injure hands.

3. Low tunnel · Locked

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4. Ventilation and fleece · Locked

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5. A small 3 × 6 m walk-in tunnel · Locked

Buy the Low tunnels and small houses module and you get the PDF to download and print, plus lifetime access to this interactive lesson: all 6 chapters, 24 steps.

6. Film, wind and snow · Locked

Buy the Low tunnels and small houses module and you get the PDF to download and print, plus lifetime access to this interactive lesson: all 6 chapters, 24 steps.