Independent reference. UK figures verified 21 June 2026. No vendor affiliation.
Finance

Cashflow + staged payments

Most UK KDR contracts use a 7-stage payment schedule with releases at deposit, foundations, plate level, roof watertight, first fix, second fix, and completion. Self-build mortgages release funds either in advance of each stage (premium rate) or in arrears (cheaper but cashflow-tight).

Oliver Wakefield-Smith · Updated 21 June 2026 · Reviewed against JCT contracts, Buildstore, FMB House Builders Cost Guide

Typical schedule

StageTypical %Trigger
1. Deposit / mobilisation5-10%Contract signed, site set-up
2. Foundations + slab15%BC inspection passed
3. Plate level20%Wall plate level, joists in
4. Roof watertight20%Roof covered, windows installed
5. First fix15%Plumbing, electrical carcass, insulation
6. Second fix15%Kitchen, sanitaryware, finishes
7. Completion5-10%BC completion certificate, snag list cleared

Mortgage release: in advance vs in arrears

In-advance products (BuildLoan, Buildstore-brokered): funds drawn at the start of each stage so contractor invoices can be paid immediately. Premium 0.5-1.0% on rate; suits cash-light builds. In-arrears products: funds drawn after each stage is certified complete; cheaper but the homeowner needs bridge cash to fund each stage before reimbursement.

Contingency

10-15% on build cost is the prudent reserve. Lower for tightly-specified contracts on stable ground; higher (15-20%) on architect-tier projects with bespoke detailing or constrained sites. Hold the contingency in cash, not as headroom on the mortgage.

JCT contract triggers

The JCT Minor Works Building Contract or JCT Intermediate Building Contract is standard on KDR. Trigger events to know: interim certificate dates, practical completion certificate, defects rectification period (typically 6-12 months), final certificate. Misalignment between mortgage release and JCT certificate can stall cashflow for 2-4 weeks.

Primary sources

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