A dakkapel (dormer) is the quickest way to turn a cramped attic into a proper bedroom or study. You gain headroom, daylight and often 4 to 8 m² of usable floor space, without touching the foundations or the facade. In 2026 a dormer costs on average €6,000 to €15,000, installed and finished. A narrow prefab plastic dormer sits at the bottom of that range; a wide made-to-measure dormer with wooden window frames, zinc cheeks and full interior finishing sits at the top.
Below you will find the guide prices by width and material, the costs that come on top for a finished room, the permit rules and the points on which to compare quotes from dormer builders. All amounts include VAT and are intended as a guide; the condition of your roof and the accessibility of the home ultimately determine the price.
Guide prices by width
| Width | Prefab plastic | Prefab wood | Made to measure (wood/zinc) |
|---|---|---|---|
| 2 metres | €6,000 – €8,000 | €7,000 – €9,000 | €8,000 – €11,000 |
| 3 metres | €6,500 – €9,000 | €7,500 – €10,500 | €9,500 – €13,000 |
| 4 metres | €8,000 – €11,000 | €9,000 – €12,500 | €11,500 – €16,000 |
| 5 metres | €9,500 – €13,000 | €10,500 – €14,500 | €13,500 – €19,000 |
Prices include VAT, installation, standard tilt-and-turn windows with HR++ glass and exterior finishing, but exclude interior finishing (plastering and painting, flooring, electrics) and any leges (municipal permit fees). A dormer at the front usually costs a few hundred to around €1,000 more because of drawings, fees and stricter requirements for its appearance and the permit procedure. So always compare quotes on the same width, the same material and the same description of what is and is not included.
What the price depends on
Prefab or made to measure
A prefab dormer is built in the factory and lifted into place with a crane in a single day. That saves labour hours and disruption: the roof is opened in the morning, and by the evening the dormer is watertight. A made-to-measure dormer is built on the roof by a carpenter and a roofer; that takes three to five days, but gives you complete freedom in size, shape and detailing, for example on a sloping roof with an unusual pitch, a listed building or a dormer that has to line up with an existing one. With a prefab dormer, always ask whether the stated width is the outside dimension or the clear opening of the window frame; that difference determines how much daylight and headroom you actually gain.
Material
- Plastic (PVC): low maintenance, affordable, limited choice of colours.
- Wood: classic look, any colour possible, needs painting every 5 to 7 years.
- Aluminium window frames with zinc or Trespa cheeks: more expensive, very long lifespan, sleek and modern.
When choosing the material, take the maintenance over the whole lifespan into account. Wood is often not much more expensive to buy than plastic, but every paint job on a roof requires scaffolding or an aerial work platform. Plastic and aluminium only need cleaning.
Glass and ventilation
HR++ is standard; triple glazing costs roughly €50 to €100 per m² more than HR++ but saves on heating costs and noise, especially for a bedroom on a busy road. A trickle vent in the window frame is sensible in a bedroom: a well-insulated attic room without ventilation quickly becomes damp. When triple glazing is worth the extra cost is explained in HR++ or triple glazing: when does it pay off.
Roof structure and accessibility
With an old or weak roof structure, purlins or an extra beam have to be added (€500 to €2,000). A roof that a crane cannot reach from the street, for example because of trees, a narrow street or a rear roof with no access, makes installation harder and more expensive; sometimes a bigger crane or a made-to-measure dormer built in sections is then the only option. That is why a good dormer builder always comes to take a look first before giving a fixed price.
Extra options
- Electrically operated roller shutters or screens: €400 – €900 per window
- Flat roof as a green roof or with solar panels: from about €600
- A nokverhoging (raising the roof ridge) or roof extension is a different category: €20,000 – €45,000
Interior finishing: do not forget these costs
The dormer itself is half the story. The builder hands over a watertight, insulated dormer, but that does not yet make the attic a room. For a finished space, the following often come on top:
- Insulating and finishing the inside with plasterboard: €800 – €1,500
- Plastering and painting: €600 – €1,200
- Electrics (sockets, lighting, possibly an extra circuit): €300 – €800
- Floor and skirting boards: €400 – €1,500
- New fixed staircase instead of a loft ladder: €1,500 – €3,500 (more if a stairwell opening has to be made)
All in all, expect €2,000 to €5,000 extra for a fully finished room, excluding a fixed staircase. Ask the dormer builder whether they can take on the interior finishing or have a regular subcontractor; otherwise you will have to schedule a plasterer, electrician and floor layer yourself once the dormer is in place. If you want to use the attic as a bedroom, also bear in mind the requirements for a fixed staircase and an escape route; a loft ladder is not enough there.
Permit or not?
A dormer at the rear (or on a side that does not border a public road) is usually permit-free if it:
- has a flat roof,
- has its bottom edge more than 0.5 metres and less than 1 metre above the dakvoet (the eaves line at the foot of the roof),
- has its top edge more than 0.5 metres below the ridge,
- stays more than 0.5 metres from the side edges of the roof surface on both sides,
- is no more than 1.75 metres high, measured from the base of the dormer,
- is not placed on a listed building or in a protected townscape or village view.
At the front an omgevingsvergunning (environmental permit) is almost always required; the municipality then also assesses it against its welstandsnota (design and appearance guidelines), for example on the proportion between the dormer and the roof surface and on how it matches the neighbours' dormers. Expect roughly €200 to €800 in fees (more if the municipality has to deviate from the omgevingsplan, the local zoning plan) and an eight-week procedure, which can be extended by six weeks. Municipalities can deviate from the national rules in their omgevingsplan, so always do the permit check on the Omgevingsloket (the government's online permit portal). Permit-free does not mean rule-free either: a permit-free dormer must also meet the building regulations and neighbour law. More on this in When do you need a permit for a renovation.
What does a dormer bring you?
A dormer usually increases the value of the home, often by more than half of the investment, especially if it creates an extra bedroom. More important for most families: you avoid an expensive move, with transfer tax, estate agent fees and a new mortgage. Dormers from before 2000 are often poorly insulated; replacing one with a well-insulated new dormer makes a noticeable difference in comfort and energy costs, and is the moment to insulate the surrounding roof surface at the same time. Do bear in mind that a dormer that does not suit the architecture of the street is more likely to be a drawback than an asset when you sell; so choose the dimensions, the window layout and the material in line with the roof surface and with what the neighbours have had installed.
How to choose a dormer builder
- Ask for at least three quotes, with the same size and specification.
- Check what is included: crane, waste removal, connection to the roof, lead flashing, guarantee.
- Ask about the guarantee on window frames (often 10 years), roof covering and installation, and who you call if there is a leak after a year.
- Look at references in your area: the same types of home give the best indication of price and workmanship.
- A good builder arranges the permit check and, if one is needed, the application including drawings.
A specialist dormer manufacturer, a contractor or a carpenter who regularly builds dormers: all three can be a good choice. The difference lies mainly in prefab versus made to measure and in who coordinates the interior finishing. Also read 5 tips for choosing the right contractor.