Home extension cost Netherlands 2026 — rear extension and side return

Quick answer

A home extension in the Netherlands costs € 1,500–€ 4,000 per m² including foundations, walls, roof and finishing in 2026. A small 15–20 m² extension: € 25,000–€ 65,000. A permit may or may not be needed depending on size and location.

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Cost by extension type

| Type | Cost per m² | Total (15–20 m²) | |---|---|---| | Simple extension (blockwork, flat roof) | € 1,500–€ 2,200 | € 25,000–€ 45,000 | | Quality living room extension | € 2,000–€ 3,200 | € 35,000–€ 65,000 | | Conservatory (aluminium frame, glass) | € 800–€ 1,800 | € 15,000–€ 40,000 | | Two-storey extension | € 2,500–€ 4,500 | € 45,000–€ 90,000 | | Attached garage | € 1,200–€ 2,200 | € 20,000–€ 45,000 |

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Detailed cost breakdown (15 m² extension, turnkey)

| Item | Cost | |---|---| | Groundworks and foundations | € 3,000–€ 8,000 | | Shell (walls, floor slab) | € 8,000–€ 18,000 | | Roof structure and finish | € 4,000–€ 9,000 | | Windows and doors | € 3,000–€ 8,000 | | Insulation (Rc ≥ 4.5 walls, Rc ≥ 3.7 floor) | € 2,000–€ 5,000 | | Services (electrics, heating) | € 2,000–€ 5,000 | | Interior finishing | € 3,000–€ 8,000 | | Architect + structural engineer | € 2,000–€ 6,000 | | Total | € 27,000–€ 67,000 |

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Permit rules (Bbl)

Permit-free (Bbl Art. 2.3):

• Extension in the rear garden area, max. 4 m high, covering ≤ 50% of rear plot
• Not higher than the adjacent roof slope of the main building
• At least 1 m from the plot boundary (or touching the neighbouring extension)

Omgevingsvergunning required:

• Front or side of the house (visible from public road)
• Exceeds height, area or boundary limits
• Protected townscape, listed building

When a permit is required: scaled drawings, BENG calculation and structural drawings are mandatory.

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BENG requirements

For extensions over 50 m²: full BENG (NTA 8800) applies. Under 50 m²: Bbl minimum thermal performance per element:

| Element | Bbl requirement | |---|---| | Flat / pitched roof | Rc ≥ 6.0 m²K/W | | External walls | Rc ≥ 4.5 m²K/W | | Ground floor | Rc ≥ 3.7 m²K/W | | Windows | U ≤ 1.65 W/m²K |

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Property value increase

Investment of € 40,000 → value increase of € 50,000 = positive return in most markets.

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Conclusion

A home extension costs € 1,500–€ 4,000 per m² in the Netherlands in 2026 — for 15–20 m² a total of € 25,000–€ 65,000. Small rear-garden extensions are permit-free. Larger or street-visible extensions need an omgevingsvergunning with an architect.

archi.sulerr.com delivers the complete permit package for your extension: sketch design, final drawings, structural calculation and BENG report.