barnconversioncost.co.uk

Self-build stage payment schedule

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.

A typical self-build mortgage releases funds at 7 milestones: land/purchase, foundations, eaves, roof watertight, first fix, second fix, completion. Each stage is independently valued by a chartered surveyor.

Typical stage release

Stage 0: purchase
up to 75% of land/purchase price
Stage 1: foundations / strip-out
15-20% of cost
Stage 2: eaves / shell
15-20% of cost
Stage 3: roof watertight
15-20% of cost
Stage 4: first fix
15-20% of cost
Stage 5: second fix
10-15% of cost
Stage 6: completion
5-10% retention release

Arrears vs advance

Arrears lenders pay after each stage is valued. Advance lenders pay at the start of each stage (better cashflow for barn conversion, which has lumpy spend). Buildstore aggregates the market.

Sources cited on this page
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Reviewed for build by O. Wakefield-Smith, Digital Signet research, Q2 2026. A chartered surveyor (RICS MRICS) sign-off is being procured for the live site. All numeric figures bracket their published BCIS, ONS or HMRC source on the page where they appear.