Prefab versus traditional dormer: the trade-off
This is your first real decision: have the dormer built in a factory and installed in one day (prefab), or built on site traditionally (3-5 days)? Prefab is cheaper and faster (€5,500-€8,500 for 3 m in 2026); traditional offers more customisation, potentially higher detail-level quality and is required in some aesthetics contexts (€7,500-€12,500 for 3 m). Prefab market share grows from 60% (2020) to 75% (2026); the quality gap has largely closed in 10 years.
- Price prefab 3 m
- €5,500 – €8,500
- Price traditional 3 m
- €7,500 – €12,500
- Install time prefab
- 1 day
- Install time traditional
- 3 – 5 days
- Prefab market share 2026
- ~75%
- Quote-to-handover prefab
- 3 – 6 weeks
- Quote-to-handover traditional
- 8 – 14 weeks
Install pace and logistics compared
Prefab: prep (remove old tiles, open subframe) in the morning, hoist 11-13h with truck-loader or mobile crane, seal and lead/zinc in the afternoon. One day total; house remains habitable overnight. No temporary cover needed, no rain-ingress risk.
Traditional: roof open for 3-5 days. Each workday covered with scaffold sheeting and building film, but rainfall (Dutch autumn/winter) creates real moisture-damage risk to bedrooms below. Ask the contractor for insurance certificate for damage liability.
Logistics: prefab needs crane setup (1 day, €280-€900 depending on district), parking permit and street closure. Traditional needs scaffold (3-5 days, €450-€1,200), material storage in garden or street. Both require coordination with neighbours and municipality.
Price difference: what you get for it
Prefab is €1,500-€3,500 cheaper at equal size and finish. The difference is standardised production (CNC sawing, line assembly), shorter on-site labour and smaller execution risks. For a standard 3 m PVC dormer on a terraced house: €5,800-€7,500 prefab vs €8,000-€11,000 traditional.
You trade 'cheaper and faster' for 'less custom and more standard look'. Prefab works in 10-20 cm size steps, standard colours (RAL 9010 white, 7016 anthracite, 9001 cream, few variants) and standard frame layout. Intermediate sizes or non-standard colour: surcharge €450-€1,500.
For most terraced and simple houses prefab is excellent. Modern prefab quality (KOMO-PVC with heat-block, Rc ≥ 4.7, HR++ glass) has improved enormously in 10 years. For architecture with character, non-rectangular geometry or heavy-aesthetics locations: traditional.
Situations that require traditional
Monuments and protected village views where aesthetics requires specific detailing (brick cheeks, ornaments, non-standard frame layout). A dormer in Amsterdam centre, The Hague Statenkwartier or Den Bosch centre is almost always traditional — surcharge €3,500-€7,500 over prefab.
Dormers with non-rectangular geometry: balcony, curved roofline, asymmetric shape, integrated rooflight in front face. Prefab factories work with straight shapes; deviant geometry requires on-site custom.
Very wide dormers (> 5 m) or very tall (> 2 m front frame): prefab elements get too heavy (> 1,500 kg) and unwieldy for crane logistics. Traditional builds modularly from the sides inward. Houses with extreme roof pitch (< 25° or > 65°) also require on-site custom.
Quality and warranty compared
Prefab benefits from factory control: every production step measured and documented. Standard warranties: 10-15 years material, 5-10 years installation. KOMO certificate gives auditable spec. Modern prefab complaints centre on installation (poor sealant finish, lead joint not flat) — not the element itself.
Traditional depends heavily on the contractor. A craftsman delivers superior quality with details no factory can match (folded zinc, brick cheeks, inset awning). An average contractor takes 5 days to deliver something comparable to prefab — just more expensive and riskier (weather, lead time).
Risk: in traditional work 'standard' doesn't exist. Always request 3 quotes on identical specs (Rc-value, glass spec, material, frame layout, colour, sealant type). Demand a handover report with photo documentation. Request at least 2 references from projects 5+ years old.
FAQ
- Is prefab always lower quality?
- No, often more consistent. Factory production removes weather dependency and human variation. 'Lower quality' experiences usually trace to thin cheek cladding or cheap frames — not the prefab principle.
- Can prefab come in any colour and size?
- No, factories work in 10-20 cm steps and standard colours. Intermediate sizes or non-standard colours mean surcharges €450-€1,500 or switching to traditional.
- When is traditional required?
- Monuments, protected cityscapes with specific aesthetics requirements, non-rectangular geometry (balcony, curved roofline), dormers > 5 m wide or > 2 m tall, roof pitch < 25° or > 65°.
- How long does each option take?
- Prefab: quote-to-handover 3-6 weeks, install 1 day. Traditional: quote-to-handover 8-14 weeks, install 3-5 days. Add 6-10 weeks for permit-bound installs.
- What do you recommend in 2026 for a terraced house?
- For a standard terraced house in a modern district: prefab with KOMO-PVC, Rc ≥ 4.7, HR++ glass, 3 m. €5,800-€7,500 including install. For heavy-aesthetics districts or special architecture: traditional or hybrid with timber cladding.