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Dormer cost · Detail

4 metre dormer cost

A 4 metre dormer adds a lot of usable space, but the wider span changes the cost structure. This guide breaks down the typical price range and what to watch for.
5 min leestijd·Onafhankelijke informatie

Short answer

A 4 metre dormer in the UK typically costs between £10,000 and £18,000, depending on material, structure, glazing and access. The wider opening usually needs more structural work than a 3 metre dormer.

Price range

  • Budget — £10,000–£13,000 with basic PVC and standard finish.
  • Mid-range — £13,000–£16,000 with good insulation, HR++ glazing and tidy finish.
  • Premium — £16,000–£22,000+ with timber or composite, triple glazing, high-end finish and full service.

Price drivers

Structural considerations

The wider the dormer, the more important the structural connection. Ask the company how the load is distributed to the existing roof and walls.

The full checklist

Checklist

4 metre dormer quote checklist

  1. 01Internal and external width are both specified as 4 metres.
  2. 02Structural reinforcement is described if needed.
  3. 03Material, frame and glazing are named.
  4. 04Insulation level is stated as a number.
  5. 05Crane and scaffolding are included or priced separately.
  6. 06Permit handling and fees are covered.
  7. 07Interior finish level is clear.
  8. 08Warranty terms are attached.

FAQ

FAQ

Veelgestelde vragen

01What does a 4 metre dormer cost?
In the UK a 4 metre dormer typically ranges from £10,000 to £18,000 or more. The wider span increases material and structural costs compared to a 3 metre dormer.
02Is a 4 metre dormer much more expensive than a 3 metre one?
Yes, usually 15–25% more. The wider opening needs more materials, more roof work and sometimes additional structural support.
03Do I need planning permission for a 4 metre dormer?
It depends on local rules and where the dormer sits. A wider dormer is more likely to need permission, especially on the front or in a conservation area.
04Can a 4 metre dormer be installed in one day?
A prefab 4 metre dormer may still be installed in one or two days, but the crane lift is heavier and the access planning is more critical.
Conclusie
A 4 metre dormer is a significant investment. The extra width is worth it for the space, but make sure the quote includes the structural and access implications of the larger size.