What actually determines the price of a dormer
Short answer
Price is driven by width, frame and cladding material, glazing type, insulation thickness, lead detail, install method, site access and permit handling. None of them is a small lever — each can move the total by €500–€3,000.
Size and shape
Width is the biggest driver: more frame, more lead, more glazing, often a crane instead of ladders. A flat-roof dormer is cheaper than a pitched one (zadeldak) because the structure is simpler. A dormer across two rafters is cheaper than one spanning three or four.
Materials and finish
- Frames: PVC (cheapest), alu-clad timber (mid), hardwood (premium).
- Cladding: PVC, Keralit, Trespa, Rockpanel, zinc — each step up adds 10–25%.
- Glazing: HR++ to triple is a meaningful step in cost and weight.
- Insulation: R 3.5 to R 5.0+ adds €300–€800 in materials.
- Lead: code 4 vs code 5, with or without corner detailing.
Site and access
A house on a wide street with parking is cheaper to work on than a narrow lane with no crane access. If the dormer needs a crane day, that is typically €600–€1,200 on its own. A bin permit, traffic-management or scaffolding adds more.
Extras and surprises
Permits, structural strengthening of the existing roof, asbestos surveys on older homes, replacing rotten battens uncovered during install — these are the line items that turn a "fixed" quote into a higher final invoice. A good company flags them up front.