Costs for a 3-metre dormer
Three metres is by far the most chosen width for a dormer in the Netherlands. It fits on most terraced houses, offers space for two window frames, and remains structurally simple. But "standard" does not mean "fixed price": the same size will result in three very different quotes from three suppliers. On this page, we explain how the price is structured, which choices carry the most weight, and how to fairly compare two offers side by side.
We don't quote rates — we explain how the price is structured.
What should a complete quote include?
A complete quote for 3 metres always includes:
- Structure: trimmer construction, possibly steel, studwork and battens.
- Exterior: roofing (EPDM, zinc, bitumen), side cheeks, fascia board, roof trim.
- Window frames: standard two window frames with HR++ glazing, tilt-and-turn or fixed panes.
- Insulation: Rc-waarde in accordance with the Bbl (Dutch Building Decree, minimum 4.7 for roofs).
- Interior finish: plasterboard, plastering, windowsill, painting, skirting boards.
- Installation: crane, demolition of existing roof surface, rubble removal.
Not automatically included: electricity, sun blinds, insect screens, floor finish, custom colours, local municipal fees, and any drawing work for planning permission.
What pushes the price up the most?
Choice of material
Plastic or polyester is affordable and low-maintenance. Timber requires painting but fits better in protected townscapes. Zinc is durable but belongs to the highest segment.
Window frame type and glazing
Two plastic window frames with HR++ glazing are the standard choice. Timber window frames or aluminium will increase this item by 20–40%. Triple glazing is a comfort gain, not a Bbl requirement.
Interior finish
A shell delivery (only structure, window frame, insulation, and exterior finishes) saves 15–25%. Complete delivery including plastering, skirting boards, and painting is much more convenient but costs more.
Accessibility
A crane costs money regardless of the width. A narrow street or a high house requires a larger crane, and that item weighs heavily.
Does planning permission count towards the costs?
On the rear roof surface of a single-family home, a dormer is often permit-free, provided it complies with the rules from the Besluit bouwwerken leefomgeving (Bbl): minimum 0.5 m from the roof eaves, no higher than 1.75 m, and keeping a set distance from the sides.
On the front roof surface — or in a protected townscape — you must apply for an environmental planning permit. Expect extra costs for drawing work, sometimes a structural engineer, and municipal fees. This should be stated separately in a quote, not hidden away in "miscellaneous".
Shell or complete — what is wise?
Shell = you get a watertight, insulated dormer with window frames, glazing, roof, and exterior finish. You do everything inside (plasterboard, plastering, windowsill, painting, electricity) yourself or outsource it separately.
A shell delivery pays off if you are a handy DIYer or have a regular handyperson. Otherwise, it is a matter of calculation: hiring a painter + plasterer + electrician separately is rarely cheaper than a complete quote. Always request both so you can see the real difference.
Fairly comparing three quotes
Make a table with these columns per supplier:
- Exterior material + brand
- Roofing (EPDM class III has the longest lifespan)
- Window frame type + brand
- Glazing (HR++ glazing or triple, U-waarde)
- Insulation (type + Rc-waarde)
- Interior finish (shell / complete / hybrid)
- Crane + accessibility (separate amount)
- VAT split (9% labour for homes >2 years old)
- Warranty periods (structure, window frame, roofing separately)
- Planning permission + municipal fees (included / excluded)
Only then may you look at the final amount. A quote that is 15% cheaper with timber window frames compared to plastic at the competitor tells a very different story than the final amount suggests.
Comparison table
| Main item | Cheapest choice | Most expensive choice |
|---|---|---|
| Exterior material | Plastic | Zinc |
| Window frames | Plastic | Timber or aluminium |
| Glazing | HR++ standard | Triple filled with argon |
| Roofing | Bitumen | Zinc |
| Finish | Shell | Complete incl. painting |
| Planning permission | Permit-free rear | Environmental planning permit + aesthetic review (welstand) |
Frequently asked questions
Short, honest answers to recurring questions.
- What does a 3-metre dormer cost on average?
- We do not mention rates. The price is not a fixed unit; it depends on material, window frame type, glazing, insulation, finish, accessibility, and permit requirements.
- Is 3 metres always permit-free?
- No. Almost never on the front roof surface. Usually yes on the rear roof surface, provided the rules from the Bbl are followed.
- Two or three window frames in 3 metres?
- Two is standard. Three is possible, but makes the window frame more complex and expensive, and reduces the individual glass areas.
- Is HR++ glazing mandatory?
- The Bbl sets requirements for the U-waarde of glazing in new facades. HR++ glazing generally complies; triple is a luxury.
- Are shell quotes always cheaper?
- On paper, yes (15–25%). In reality, only if you arrange the interior finish yourself or via your own handyperson.
- How long does installation take?
- Prefab: 1 day installation + 2–3 days interior finish. Traditional on-site: 5–7 working days in total.
- Is scaffolding included as standard?
- Often included with prefab, not always with traditional. Request a specification.
- Is 3 metres better than 4 metres in terms of price-per-metre?
- 4 metres has a slightly more favourable price-per-metre, because the fixed costs are distributed over more metres.
- Do I get a discount for multiple dormers?
- Sometimes, but the difference is smaller than expected because each dormer retains its own installation, crane, and finishing.
- What is a trimmer construction and does it cost extra?
- A trimmer construction supports the cut purlins. With 3 metres, this is standard and should be included in the base price.
Summary
Three metres is the most commonly chosen width and has the most favourable price-per-metre compared to a 2-metre dormer. The fixed costs (crane, startup, removal) are distributed over more material. The largest price differences arise from material, window frame type, glazing, and the choice between shell or complete. Make a table with identical specifications for three quotes — only then will you see the real difference.