Cost guide
How much does a dormer loft conversion cost?
The published UK average for a dormer conversion specifically, alongside our general loft conversion cost guide.
A dormer loft conversion costs around £45,000 on average in the UK, according to MyJobQuote, broadly in line with Checkatrade's general dormer conversion average of around £50,000. For rooflight, hip-to-gable and mansard comparisons, see our general loft conversion cost guide.
Last updated 20 August 2026
| Range | ||
|---|---|---|
| UK average (MyJobQuote) - published as a single average, not a range | £45,000 | Total project |
| UK average (Checkatrade, general house) - published as a single average, not a range | £50,000 | Total project |
Sources: MyJobQuote (UK average, checked August 2026), Checkatrade (general house dormer average, checked August 2026)
Worth knowing
Checkatrade's loft conversion cost page presents a further property-type breakdown for dormer conversions that we found ambiguous in the published snippet - rather than over-interpret it, we've cited only the clearly-stated UK average figures here.
Key points
- Dormer size - a single small dormer costs less than a full-width dormer spanning the roof slope.
- Whether the project adds an en-suite bathroom, which brings in new plumbing runs.
- Structural work to strengthen the floor for habitable-room loading.
- Roof window specification and how the dormer's flat roof ties into the existing roofline.
These are general published ranges, not a quote. Get an estimate based on your own project.
Start Your ProjectWant to understand what drives this cost, not just the numbers? Read how long does a loft conversion take? →
Looking at how much does a dormer loft conversion cost?? See how we approach it →
Other cost guides
More published cost ranges
How much does a loft conversion cost?
Published industry ranges by conversion type, so you can budget sensibly before getting a quote.
How much does a house extension cost?
The published UK per-m² rate for a single-storey extension, and what actually moves it.
How much does a two storey extension cost?
Published per-m² rates by build quality, and what a typical two-storey extension runs in total.
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