Barn conversion services cost
Costs verified against BCIS Online (May 2026 release) and ONS Construction Output Price Index, April 2026. Class Q rules current to the 21 May 2025 GPDO amendment.
M&E layer typically adds £55,000 to £130,000 to a rural barn conversion, depending on which services are present. Off-grid drainage is almost universal; an ASHP or GSHP plus borehole and three-phase upgrade can together cost more than the new kitchen.
The rural M&E stack
Off-grid sewage treatment plant
£8,000 - £18,000
ASHP, installed, post-BUS grant
£11,000 - £18,000
GSHP, installed, post-BUS grant
£22,000 - £35,000
Borehole + UV treatment
£8,000 - £14,000
Three-phase electricity upgradeDNO-quoted, contestable
£8,000 - £40,000
BNG (10%, on full planning route)
£2,000 - £12,000
Bat survey (Phase 1 + emergence)
£900 - £3,500
Ecology and arb reports
£2,000 - £6,000
What drives the spread
The DNO three-phase quote is the most volatile line. Distance to the nearest three-phase main, ground conditions and need for a new transformer all push the bill. Get a budget quote early; Ofgem rules require the DNO to provide a price within 60 working days of formal request.
Sources cited on this page