Building a sunroom yourself costs €3,000 to €15,000 in materials for a standard lean-to, depending on material, size and specification. Having a sunroom built by a specialist: €8,000 to €40,000.
What Does a Sunroom Cost? DIY vs. Specialist
Cost Comparison
| Type | Size | DIY (materials) | Specialist (all-in) | Saving |
|---|---|---|---|---|
| Small lean-to sunroom (cold) | 6–9 m² | €3,000 – €6,000 | €8,000 – €15,000 | €5,000 – €9,000 |
| Standard sunroom (heated) | 10–15 m² | €6,000 – €10,000 | €15,000 – €25,000 | €9,000 – €15,000 |
| Large sunroom | 20–30 m² | €10,000 – €18,000 | €25,000 – €45,000 | €15,000 – €27,000 |
| Timber conservatory (bespoke) | 10–15 m² | €5,000 – €12,000 | €15,000 – €30,000 | €10,000 – €18,000 |
Cold vs. Warm Sunroom
Cold Sunroom (Unheated)
- Not heatable, max 5–10°C in winter
- Simpler construction, less expensive
- Suitable as a transition space, for winter-hardy plants
- Glazing: single or standard double
Warm Sunroom (Heated Living Space)
- Part of the living area, usable year-round
- Connected to central heating or standalone heating
- High-performance triple glazing required
- More expensive but much better quality of life
Planning Permission
In most countries an extension to the house (which a sunroom is) requires planning permission or building regulations approval. Permitted development rules may apply in some cases:
- Check with your local council / planning authority before starting
- Rules vary significantly by country, region and local authority
- Always get written confirmation
Materials List: Lean-to Sunroom 12 m² (3×4 m)
| Material | Quantity | Approx. Cost |
|---|---|---|
| Aluminium sunroom kit (12 m²) | 1 unit | €4,000 – €8,000 |
| Foundation (concrete strip or slab) | 12 m² | €600 – €1,500 |
| Wall plate / coping | 1 unit | €80 – €200 |
| Roof glazing (triple, 12 m²) | 12 m² | €600 – €1,500 |
| Side glazing (triple) | 15 m² | €750 – €1,875 |
| Heating connection (radiator) | 1–2 units | €300 – €800 |
| Blinds or external shutters | Depending on size | €500 – €2,000 |
| Ventilation rooflights (electric) | 2–3 units | €300 – €800 |
Step-by-Step: Build a Sunroom in 9 Steps
Step 1: Design and Planning Permission
- Draw floor plan and section with accurate dimensions
- Apply for planning permission / building regulations approval
- Engage an energy consultant for heating design in a heated sunroom
- Order the kit from the manufacturer – allow 4–8 weeks for delivery
Step 2: Lay the Foundation
Option A: Concrete strip foundation:
1. Dig a strip foundation 30 cm deep and 30 cm wide around the perimeter
2. Install reinforcing steel
3. Pour B25 concrete and allow 7 days to cure
4. Foundation must be below the frost line (min. 80 cm in cold regions)
Option B: Concrete floor slab (simpler):
1. Excavate 30 cm
2. Hardcore 20 cm, compacted
3. PE membrane, reinforcing mesh
4. Pour 12 cm concrete
5. Screed flat and allow 7 days to cure
Step 3: Prepare the House Wall
- Clean the wall surface where the sunroom attaches
- Drill fixings for the wall plate
- Fix the wall plate with suitable fixings
- Apply pre-compressed foam seal behind the plate for weathertightness
Step 4: Assemble the Base Frame
- Lay the base profiles (cill) on the foundation
- Anchor to the foundation
- Level precisely – this is the most critical step
- Connect the corners
Step 5: Build the Wall and Roof Frame
- Erect the vertical profiles
- Fix the head rail
- Install the roof rafters
- Check plumb and level throughout
- Tighten all connections
Step 6: Install the Glazing
- Fit glazing gaskets in the frames
- Set the panes (roof from inside out)
- Fix the retaining beads
- Check all weather seals
Step 7: Fit the Door and Windows
- Insert door frame
- Hang and adjust door
- Fit ventilation rooflights
Step 8: Connect the Heating
For a heated sunroom:
1. Have the heating engineer extend the central heating circuit
2. Install radiators
3. Electric underfloor heating as an alternative
Step 9: Interior Fit-Out and Finishing
- Lay the floor (porcelain tiles, decking or laminate)
- Silicone all internal junctions
- Install electrical circuits (qualified electrician)
- Fit blinds/shutters
Common Mistakes
| Mistake | Consequence | Solution |
|---|---|---|
| No planning permission | Enforcement notice, demolition order | Always check before starting |
| Shallow foundation | Frost heave, cracking | Minimum 80 cm deep |
| Insufficient ventilation | Overheating, condensation | Min. 15% of roof area openable |
| No solar shading | Unusable in summer | Fit external blinds or an awning |
FAQs
What does a sunroom cost?
DIY: €3,000–€10,000 in materials. Specialist: €8,000–€40,000 depending on size and specification.
Do I need planning permission?
In most cases yes, since a sunroom is an extension to the house. Rules vary by country and local authority – always check before starting.
Can I use it in winter?
Only a heated sunroom with triple glazing can be comfortably used in winter. An unheated sunroom will be cold.
Building Plans and Guides
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