Costs of having a dormer installed

How does the process work?

A typical process from quote to handover (oplevering):

1. Initial contact and rough quote (week 1) — the supplier asks for the size, material, and roof surface. 2. On-site measurement (week 2) — exact measurements, photos, assessment of accessibility and existing construction. 3. Final quote (week 2–3) — itemised according to the categories mentioned above. 4. Order and deposit (week 3) — usually 25–40% deposit. 5. Planning permission process (week 3–11) — only if a permit is required. Skip if permit-free. 6. Production (week 6–10) — prefab suppliers produce in parallel. 7. Installation (week 10–12) — usually 1 day for prefab, 4–7 days traditionally built. 8. Interior finishing (week 11–13) — 2–5 days. 9. Handover and final payment (week 13–14).

For permit-free installations, you can shorten this timeline by 4–6 weeks.

What should a complete quote include?

A fair quote specifies:

• Exterior material: type and brand (e.g., "Trespa Meteon" or "Polyester sandwich 6 mm").
• Roof covering: EPDM (class), zinc (thickness), or bitumen (number of layers).
• Construction: timber or steel, and whether a structural engineer is involved.
• Window frames: number, type, brand, layout (tilt-and-turn / fixed).
• Glazing: HR++ / HR+++ glazing, U-value, gas filling.
• Insulation: type (PIR, mineral wool) + Rc-waarde.
• Interior finishing: structural shell (casco) / complete, explicitly stating what is included/excluded.
• Installation: crane (size), demolition, disposal, possibly scaffolding.
• Planning permission: municipal fees (leges) and technical drawings included/excluded.
• VAT split: 9% on labour / 21% on materials for homes > 2 years old.
• Warranty: listed per component separately.
• Payment terms: deposit, interim payment, handover.

A quote without this breakdown is not a quote but a total price without justification.

How do you recognise a professional supplier?

Signs of craftsmanship:

• Knowledge of the local municipality — knows the aesthetic review (welstand) requirements for your postcode.
• On-site inspection — measures in person, asks for photos of the loft.
• Structural engineer partner — has a regular structural engineer, knows when structural calculations are needed.
• Layered warranty — provides a term per component (not just '10 years on everything').
• References — can point out recently installed dormers in your region.
• Clear communication — answers technical questions without evasion.
• Trade association — e.g., a member of Bouwend Nederland or another professional body.

Red flags:

• No on-site measurement (only via phone / photos).
• Vague or unspecifed quote.
• "Once-in-a-lifetime opportunity" or large discount for deciding quickly.
• High deposit (>50%).
• No written warranty or clear warranty conditions.

Comparing three quotes side by side

The only fair comparison is based on identical specifications. Ask each supplier for:

• Same width and height.
• Same exterior material.
• Same window frame type and glazing U-value.
• Same insulation Rc-waarde.
• Same finishing (structural shell or complete — choose one variant).
• Planning permission included/excluded — choose one variant.

If quotes differ on any of these points, request an adjustment. Only then are you comparing euros with euros. A 15% lower amount for thinner insulation or a timber window frame instead of aluminium tells you next to nothing.

Common mistakes made by customers

• Choosing based on the final price without comparing specs.
• Not discussing planning permission — returns later as additional costs.
• Accepting a high deposit without a guarantee arrangement.
• Not asking for written warranty conditions.
• Not looking at references — ask specifically about a recently installed dormer.
• Underestimating accessibility — the crane needs to be able to reach your property.
• Forgetting electrics, sun blinds, fly screens as requirements — having this done afterwards is more expensive.

Frequently asked questions

Short, honest answers to recurring questions.

What does it cost to have a dormer installed?

We do not list prices. The cost depends on the width, material, window frame type, glazing, insulation, finishing, and accessibility.

How long does the entire process take?

6–14 weeks from quote to handover, depending on whether planning permission is required.

What is a customary deposit?

25–40% upon commissioning. Anything above 50% is a red flag.

Which VAT rate applies?

9% on labour for homes older than 2 years; 21% on materials. This must be split in the quote.

How many quotes should I request?

At least three, with identical specifications.

What if I want to adjust my dormer after commissioning?

Expect additional costs. Changes after production has started are often expensive or no longer possible.

Is a dormer insured during installation?

Yes, via the contractor's CAR (Construction All Risk) insurance. Request proof of this.

What if I am not satisfied at handover?

Create a snagging list with action points. A good contractor will resolve them within 2–4 weeks. Withhold the final payment until the repairs are completed.

Can I pay in instalments?

Generally there are three payment moments: deposit, interim, and handover.

What is the customary warranty period?

It should be layered: construction 10 years, window frames 10 years, glazing 10 years (including argon), roof covering 10 years, sealant 5 years.

Summary

Having a dormer installed is the logical choice for most people. The process takes 6–14 weeks; the quote should be specified by construction, material, window frames, glazing, insulation, finishing, installation, and planning permission. Request at least three quotes with identical specs, do not accept a deposit above 40%, and demand layered warranty conditions. A professional supplier will measure on site, knows your municipality, and partners with a structural engineer.