Construction · Detail
Prefab dormer vs built on site
Prefab and traditional on-site construction both work. The right choice depends on your roof, your timeline, and how much customisation you need.
6 min leestijd·Onafhankelijke informatie
Short answer
Prefab dormers are faster and made in a factory, which suits standard roofs and tight schedules. On-site construction takes longer but handles unusual shapes, listed buildings and fully bespoke designs.
Comparison
| Factor | Prefab | Built on site |
|---|---|---|
| Speed | 1–2 days on site | 2–5 days on site |
| Quality control | Factory conditions | Depends on crew experience |
| Customisation | Standard sizes and options | Almost any shape |
| Crane | Usually required | Sometimes not needed |
| Weather risk | Lower | Higher |
| Cost | Often slightly lower | More labour, more flexibility |
Prefab dormer
The dormer is built in a factory and delivered as a complete unit. The roof is opened, the box is lifted in, and the crew seals the joints. Most of the work happens off-site, so disruption is minimal.
Built on site
The frame is built piece by piece on the roof. It takes longer and creates more mess, but it allows exact matching of an existing roof and full control over materials.
FAQ
FAQ
Veelgestelde vragen
4 vragen · klik om te openen
01Is a prefab dormer cheaper than building on site?
Often slightly cheaper, but the difference is smaller than people expect. The main saving is time, not always material quality.
02Which is better quality: prefab or built on site?
Both can be excellent. Prefab is built in a factory under controlled conditions; built on site allows more customisation and can suit unusual roofs.
03Can a prefab dormer be customised?
Yes, within standard ranges. Size, window layout, cladding and colour can usually be chosen. Very bespoke shapes are easier to build on site.
04Does a prefab dormer need a crane?
Yes, almost always. The factory-built box is lifted onto the roof by crane, which adds to cost and access planning.
Conclusie
Neither method is automatically better. Prefab wins on speed and consistency; on-site wins on flexibility. Match the method to your roof, not to a sales pitch.