A home extension is one of the most popular ways to create additional living space without moving house. But what does an extension actually cost? Below you will find a realistic overview of the costs in 2026, including price per m2, practical examples for 15, 20, and 25 m2, foundations, interior finishing, and choices that make a quotation more affordable or more expensive.
Quick answer: extension costs per m2 in the Netherlands
In the Netherlands in 2026, an extension usually costs between €2,200 and €4,500 per m2 based on standard, usable turnkey finishing. Shell construction (casco) can be lower, while luxury bespoke work, large expanses of glass, underfloor heating, structural load-bearing alterations, or complex foundation conditions will drive the price up. For an extension of 20 m2, the total indicative price often ranges between €44,000 and €70,000.
Looking for a quick calculation before requesting quotes? Use this straightforward guide:
| Question | Guideline Value |
|---|---|
| Basic budget | Number of m2 x €2,200 |
| Comfortable budget | Number of m2 x €3,200 |
| Luxury or complex budget | Number of m2 x €4,500 or more |
This calculation is meant for orientation. An actual quotation depends on the existing facade, ground conditions, site accessibility, window frames, roof structure, insulation, installations, and interior finishes. Heidstra Bouw therefore always carries out an on-site survey in Friesland, Groningen, or Drenthe before providing a fixed price.
Average costs of an extension
The costs of an extension vary from house to house. Size, foundation, accessibility, choice of materials, and finishing standard have a substantial impact. The amounts below are rough indications. An extension may turn out cheaper or more expensive due to soil conditions, structural alterations, windows, glazing, building services, and finishing. An on-site survey is necessary for an exact price. Feel free to request a free quote.
| Type of extension | Indicative price |
|---|---|
| Small bump-out of 2 to 3 m2 | €8,000 to €20,000 |
| Medium-sized extension of 5 to 10 m2 | €15,000 to €40,000 |
| Large extension of 10 to 20 m2 | €35,000 to €60,000 or more |
| Two-storey extension | €45,000 to €85,000 or more |
Extension costs per m2 in 2026
Many homeowners search for the cost of an extension per m2 in the Netherlands. That serves well as an initial guideline, but the price per m2 often decreases for larger extensions because fixed overheads are distributed over more square meters.
| Finishing level | Cost per m2 |
|---|---|
| Shell (casco) extension | €1,600 to €2,400 per m2 |
| Standard turnkey finish | €2,200 to €3,200 per m2 |
| Luxury finish | €3,200 to €4,500 per m2 |
| Complex bespoke build | from €4,500 per m2 |
A small bump-out of 3 meters depth may be more expensive per m2 than a larger extension because foundation work, site setup, connection to the existing property, and building services are always required regardless of size.
Sample calculation
Suppose you want to build an extension of 20 m2. You can use the following estimates for an initial budget:
| Scenario | Calculation | Indicative price |
|---|---|---|
| Shell or simple | 20 m2 x €1,600 to €2,400 | €32,000 to €48,000 |
| Standard turnkey | 20 m2 x €2,200 to €3,200 | €44,000 to €64,000 |
| Luxury finish | 20 m2 x €3,200 to €4,500 | €64,000 to €90,000 |
On top of this, additional costs may arise for a wide wall knock-through, structural steel beam, large sliding doors, skylights/roof lanterns, underfloor heating, kitchen preparations, or repair work to the existing house.
What makes up the costs?
An extension consists of multiple components, each with its own budget:
Foundation: €2,500 to €8,000
The foundation is the bedrock. Depending on soil mechanics, strip footings, concrete pad footings, or a full raft slab may be chosen. In Northern Netherlands, with its occasionally soft peat or clay soils, an engineered foundation is doubly important.
Structure: €5,000 to €20,000
The load-bearing framework of walls, roof, and any steel sections. Timber-frame construction (HSB) is often more cost-effective than traditional masonry.
Roof: €2,500 to €7,000
A flat roof is more affordable than a pitched roof. EPDM membrane roofing is popular due to its exceptionally long lifespan.
Interior finishing: €3,500 to €12,000
Plastering, painting, flooring, lighting, and optional underfloor heating. The choice of materials and finishing standard largely determines the final figure.
Building services: €1,500 to €4,000
Electrics, heating, and any water supply and drainage pipework within the extension.
Examples by dimensions
The examples below provide a quick impression of frequently requested extension sizes. The actual price depends on the home, foundation, existing facade, selected finishes, and site accessibility. For a more detailed breakdown by size, also read extension costs 15m2, 20m2 and 25m2.
| Size | Global costs |
|---|---|
| Extension 15 m2 | €33,000 to €55,000 |
| Extension 20 m2 | €44,000 to €70,000 |
| Extension 25 m2 | €55,000 to €85,000 |
| Extension 60 m2 | from €120,000 |
What does a 3-meter extension cost?
A 3-meter deep extension typically costs between €25,000 and €60,000, though this remains an indicative range. The difference lies mainly in overall width, foundations, window frames, patio doors, skylights, underfloor heating, and interior finishes. A glass facade or premium sliding door increases the project cost, but delivers abundant natural daylight and a generous sense of space.
Extension foundation costs
The foundation often costs between €2,500 and €8,000, but in soft ground or with restricted machinery access, this can rise significantly. In certain areas of Northern Netherlands, extra attention must be paid to bearing capacity and ground settlement. That is why we always examine site conditions locally before quoting a fixed sum. Read more in extension foundation costs.
Factors that influence the price
- Size: more square meters = higher total expenditure
- Materials: standard versus luxury specification
- Foundations: determined by geotechnical ground conditions
- Complexity: corner configurations, roof shapes, bay projections
- Location: accessibility of the building plot and materials handling
Real-world project: Extension on Nieuwstad, Groningen
On the Nieuwstad in Groningen, we are currently realizing a substantial rear extension combined with a complete roof renovation. The project encompasses a rear extension, complete roof overhaul, three new dormer windows, and facade restoration. This is a prime example of a complex project in a dense urban setting. Find more information on our service page for extensions and bump-outs.
Practical tips when planning an extension
- Start with sound design: ensure the extension seamlessly integrates with the existing architecture
- Choose quality materials: an extension is a long-term capital investment
- Plan in the dry season: foundation and structural groundwork progress faster in dry weather
- Demand a detailed quote: itemizing every component and phase clearly
Looking to tighten your budget? Check early whether an extension permit in 2026 is needed, and use our checklist for comparing contractor quotes. With an older property, it is also wise to account for renovation costs and hidden defects.
Regional price variations
Extension costs vary not only by building type, but also by region. In an urban center, accessibility costs more due to restricted storage space, parking permits, and material deliveries. In rural areas, travel distances, soil conditions, or exposed locations can influence logistics and foundation work. Heidstra Bouw operates across Friesland, Groningen, and Drenthe. See also our articles on extension in Drenthe, extension in Leeuwarden, and our service page extensions and bump-outs.
Frequently asked questions about extension costs
What does an extension cost per m2 in 2026?
Expect generally between €2,200 and €4,500 per m2 for a fully usable, completed extension. Shell construction can be lower; bespoke luxury or complex structural work higher.
What does a 20 m2 extension cost?
A 20 m2 extension typically costs between €44,000 and €70,000 with standard finishing. With high-end finishes or extensive structural knock-throughs, this will increase.
Why is a small bump-out relatively expensive?
Foundations, tie-ins to the existing facade, roof junctions, electrics, and site setup are always necessary. Consequently, fixed overheads are spread over fewer square meters.
Is a bump-out cheaper than an extension?
In practice, these terms are often used interchangeably. The actual price depends primarily on size, foundation, structural framework, windows, roof, and interior finishes.
Free quotation for your extension
Considering an extension? Heidstra Bouw builds extensions across Friesland, Groningen, and Drenthe. Contact us for a free consultation and itemized quote via info@heidstrabouw.nl or call 06-36549707. That way you know exactly what an extension will cost in your situation, rather than relying solely on general guidelines. For regional information, visit building company Friesland, building company Drenthe, building company Leeuwarden, and building company Buitenpost.
