Building Your Own Greenhouse: Planning, Foundation & Construction

Your own greenhouse extends the growing season by weeks, protects sensitive plants from frost and moisture, and allows you to raise heat-loving crops like tomatoes, peppers and cucumbers. With the right planning, it's manageable even for beginners.

Which Greenhouse Suits You?

By Material

• Aluminum greenhouse – lightweight, rust-free, affordable (from €300), good kits available
• Wooden greenhouse – visually appealing, good insulation, needs regular maintenance
• Polytunnel – cheapest option (from €50), not permanent, ideal for beginners

By Glazing

• Single glass – cheap, high light transmission, risk of breakage
• Twin-wall polycarbonate sheets – shatterproof, good insulation, slightly yellowish, ideal for beginners
• Toughened glass (tempered safety glass) – expensive, but durable and clear

Choosing a Location

• South-facing – at least 6 hours of sun daily
• Wind protection at the back (hedge, fence, house wall) – but without casting shade
• Water connection nearby
• Level ground – or plan for terracing
• Minimum distance to property lines: 1–3 m depending on the state (ask the building authority for areas over 20 m²)

Foundation – The Decisive Base

Point Foundation (Simple)

For smaller greenhouses up to ~15 m². Concrete posts or ground sleeves set in concrete at the corners and midpoints. Affordable and sufficiently stable.

Strip Foundation (Solid)

Continuous concrete foundation (~20 cm deep, 20 cm wide). For large greenhouses or soft ground. Durable and frost-proof.

No Foundation

Only suitable for temporary polytunnels. Ground screws or earth anchors are sufficient.

Setup Step by Step

1. Mark out and level the area – set up string lines, remove/add soil until everything is level
2. Set the foundation – dig holes, set sleeves/posts in concrete, let cure (at least 3 days)
3. Erect the frame – kits usually come with instructions; align corners exactly at 90°
4. Assemble the roof structure – attach rafters and ridge, check roof pitch (30–35° optimal)
5. Install the glazing – fit panels from bottom to top, secure with clips or rubber profiles
6. Door and vent windows – plan for at least one roof window for natural convection

Interior Fittings

• Raised beds or beds directly in the ground – refresh soil with compost
• Shelving for seedling pots – wire shelving along the walls
• Irrigation system – drip irrigation with a timer saves time daily
• Thermometer/hygrometer – min-max thermometer to track extremes

Ventilation and Temperature Control

In summer, the greenhouse can reach 60°C+. This kills plants quickly:

• Roof windows that open automatically via a thermostat opener (from €15)
• Shade netting on the south side during strong sunlight
• Supplemental heating in spring: a small electric heater is enough for frost-free nights

Permits

Greenhouses up to approx. 20 m² are permit-free in most German states – but it's still worth checking with the local building authority, especially near property boundaries.