Roof extensions — Amsterdam, Amstelveen, Haarlem & Zaandam
Build a roof extension
A complete extra floor: new bedrooms and a bathroom without losing a single metre of garden.
- a complete extra floor
- +25–40 m²
- to make weatherproof
- 2–5 days
- estimate incl. VAT
- €45k–120k
What a roof extension adds
The space of a larger house, without moving
A roof extension replaces a pitched or flat roof with a full new storey. Growing families keep their neighbourhood, school and mortgage while gaining the two bedrooms and second bathroom they would otherwise move for.
A complete additional floor
A roof extension replaces a pitched or flat roof with a full storey; two bedrooms and a bathroom are the most requested layout.
No need to move
Growing families keep their neighbourhood, school and mortgage while gaining the space of a larger home.
Built to current insulation standards
The new envelope uses Rc 6.3 roof insulation, Rc 4.7 walls and HR++ or triple glazing for noticeably better comfort.
Permit & structure
Calculate first, promise second
A roof extension almost always requires a permit because it changes the height and streetscape. The municipality reviews building height, design quality and shadow impact. We submit drawings, calculations and a shadow study as one complete file.
Before preparing a quote, our structural engineer checks whether the foundation, walls and floors can carry the added load. Lightweight timber framing often avoids foundation reinforcement.
We build the new envelope to current standards and, where required, coordinate independent quality assurance and the handover file.
Construction method
Light, fast and carefully prepared
Workshop-prepared timber elements reduce both added weight and the number of days your house is exposed to the weather.
Structural check first
Foundation, load-bearing walls and floor capacity are assessed before a design is promised.
Weatherproof in days
The existing roof is removed and prepared elements are craned into place, normally closing the house in two to five days.
A complete new envelope
Rc 6.3 roof, Rc 4.7 walls and HR++ or triple glazing create the best-insulated floor in the house.
Process
How the new floor is added
- 01
Structural assessment
Our engineer checks the foundation and load paths before we propose a design.
- 02
Design & permit
We develop a streetscape-sensitive design and submit calculations and a shadow study.
- 03
Workshop preparation
Timber-frame elements are prepared before the roof is opened.
- 04
Crane day & interior
The structure is weatherproof in days, followed by three to five weeks of staircase, bathroom and finishing work.
Costs
Roof-extension cost estimate
The existing structure and level of finish determine the range. These are realistic 2026 figures including 21% VAT.
| Specification | Estimate (per project) |
|---|---|
| Shell roof extension on a terraced house | €45,000 – €70,000 |
| Fully finished, including staircase | €70,000 – €95,000 |
| Turnkey, including bathroom | €95,000 – €120,000 |
Estimate including 21% VAT, 2026 price level. The existing structure and roof type determine the range; our engineer checks this in advance.
Projects
Roof extensions we have built
Frequently asked questions
What clients ask us before starting
That is the first thing our structural engineer checks. Timber-frame construction keeps the added weight low, so many terraced and semi-detached homes can be extended without strengthening the foundation.
Can your home carry another floor?
Our engineer will assess the starting point during a free consultation, so you know what is realistic before committing.
contact@renovaco.nlKvK 92576907