Building a greenhouse yourself costs on average €300 to €1,500 in materials. Buying a ready-made greenhouse and having it installed costs €1,500 to €6,000. Building a solid greenhouse yourself is very achievable with basic tools.
What Does a Greenhouse Cost? DIY vs. Ready-Made
Cost Comparison
| DIY (materials) | Having it installed | |
|---|---|---|
| Small greenhouse (4–6 m², aluminium kit) | €300 – €600 | €900 – €1,800 |
| Medium greenhouse (8–12 m², aluminium) | €600 – €1,200 | €1,500 – €3,000 |
| Large greenhouse (16–25 m², aluminium or timber) | €1,000 – €2,500 | €2,500 – €6,000 |
| Wooden greenhouse to measure (4–8 m²) | €500 – €1,000 | €1,500 – €4,000 |
| Polycarbonate greenhouse (budget, 6–10 m²) | €250 – €700 | €800 – €2,000 |
Aluminium vs. Wooden Greenhouse
| Aluminium greenhouse | Wooden greenhouse | |
|---|---|---|
| Maintenance | Almost none | Annual painting or oiling |
| Lifespan | 20–40 years | 15–30 years (with maintenance) |
| Appearance | Modern, slim | Warm, classic |
| Material price | €300 – €2,500 (kit) | €400 – €2,000 (self-build) |
| Working with it | No cutting, uses clips | Normal carpentry |
| Insulation | Moderate (cold bridges) | Better (wood insulates) |
Choose aluminium for low maintenance and a clean modern look. Aluminium kits are also easier to assemble.
Choose wood for a more traditional look or when you need custom dimensions.
Glazing: Glass vs. Polycarbonate
| Toughened glass | Polycarbonate (6 mm) | Polycarbonate (16 mm) | |
|---|---|---|---|
| Light transmission | ~90% | ~80% | ~75% |
| Insulation | Moderate | Moderate | Good (twin-wall) |
| Price per m² | €15 – €30 | €8 – €15 | €15 – €25 |
| Lifespan | 20+ years | 10–15 years | 15–20 years |
Toughened glass gives the best light transmission. 16 mm polycarbonate is the best balance: safe, lightweight and reasonably insulating.
Materials List: Greenhouse of Approx. 8 m² (2.5 x 3.2 m)
Foundation Materials
| Material | Quantity | Approx. Cost |
|---|---|---|
| Concrete mix (25 kg bags) | 8–10 bags | €40 – €70 |
| Corner anchors or ground stakes (steel) | 4–6 pieces | €20 – €50 |
| Concrete blocks for foundation perimeter | 1 m² | €15 – €30 |
| Sand (washed, for bedding) | 200 kg | €10 – €20 |
| Weed control membrane | 5 metres | €8 – €15 |
Construction Materials (Aluminium Kit)
| Material | Quantity | Approx. Cost |
|---|---|---|
| Aluminium greenhouse kit (8 m²) | 1 unit | €450 – €900 |
| Extra ventilation panels (roof vents) | 1–2 pieces | €40 – €100 |
| Door closer or hook | 1 piece | €10 – €20 |
| Sealing rubbers | 1 set | €10 – €20 |
| Stainless steel screws and bolts | 1 set | €10 – €15 |
Total materials: €560 – €1,150
Step-by-Step: Build a Greenhouse in 9 Steps
Step 1: Choose the Right Location
- At least 6 hours of direct sunlight per day
- Orient the ridge east-west for maximum sun on both long sides
- Avoid spots under trees – falling branches damage glazing
- Choose a level site (max. 3% slope)
- A partially sheltered position is better than fully exposed
Step 2: Check Planning Permission
Usually no planning permission needed for a freestanding outbuilding up to 15 m² in the rear garden.
– Maximum height without permission: 2.5 m (flat roof) or 3 m (pitched roof)
– Always check with your local council.
Step 3: Mark Out and Excavate
- Mark out the outer dimensions with string and stakes
- Check diagonals are equal
- Dig a shallow trench 20–30 cm deep and 20–25 cm wide along the outer perimeter
Step 4: Lay the Foundation
Method A – Concrete blocks on sand bed (simple):
1. Lay 10 cm of sand in the trench
2. Set concrete blocks level
3. Allow 24 hours to cure
Method B – Poured concrete (more stable):
1. Mix concrete (1 part cement, 2 parts sand, 3 parts gravel)
2. Pour to 5 cm below ground level
3. Allow at least 2 days to cure
Step 5: Assemble the Base Frame
- Lay the base profiles on the foundation
- Connect corners with supplied corner pieces
- Check the base is precisely level – this is the most critical step
- Fix the base frame to the foundation
Step 6: Build the Wall Sections
- Mount the vertical corner profiles and intermediate uprights
- Use supplied clips or bolts – don’t fully tighten yet
- Check plumb on two sides with a spirit level
- Set the top rail
- Tighten all connections
- Mount the roof structure following kit instructions
Step 7: Fit the Door and Vents
- Mount the door frame in the designated opening
- Hang the door on its hinges
- Adjust the door for smooth operation
- Fit the roof vents at the top
Tip: Plan at least 2 roof vents per 6 m² of greenhouse floor area.
Step 8: Install the Glazing
- Start with the lower side panels and work upwards
- Fit the sealing rubbers in the profiles before inserting glass or polycarbonate
- Slide panels into the top and bottom grooves and clip in place
- Roof panels: work from the bottom up so rain can run off
Step 9: Finishing and Setting Up
- Seal joints on the outside with clear silicone
- Lay the floor – paving slabs, a gravel path or just soil for direct planting
- Prepare growing medium (garden soil mixed with compost 1:1)
- Position a water butt next to the greenhouse
- Fix shelves or staging along the sides
Common Mistakes
1. Foundation Not Level
Most common mistake. Even 5 mm out causes problems: gaps in glazing, doors that won’t close.
2. Insufficient Ventilation
Without roof vents, the greenhouse becomes an oven in summer. Minimum 20% of the roof area must be openable.
3. No Weed Membrane on the Floor
Without a base, weeds grow up through the floor.
FAQs
How big can a greenhouse be without planning permission?
In most areas, an outbuilding up to 15 m² in the rear garden is permitted development, provided it is more than 1 metre from the boundary and no taller than 3 metres.
How long does an aluminium greenhouse last?
20 to 40 years with normal use. Aluminium doesn’t rust.
Can I use a greenhouse year-round?
Yes, but a standard greenhouse insulates poorly. For winter use you need 16 mm polycarbonate and possibly a small heater.
Building Plans and Guides
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