Decision worksheet
Before you lock a greenhouse construction contingency into the budget, decide whether you are carrying one risk or four: unresolved scope, escalation timing, owner-driven changes, and site risk. A split allowance is better when those drivers are still moving; a single blended reserve is only defensible when the scope matrix, procurement timing, and site inputs are already stable enough to support final approval.
| Budget question | Better treatment | Decision test |
|---|---|---|
| Is scope still incomplete? | Keep a separate line for exclusions, interfaces, and unpriced work | If the supplier has not priced utility tie-ins, controls interfaces, or commissioning, that gap belongs outside the base quote |
| Is the market window moving? | Track escalation as its own allowance | If quote validity is shorter than your approval cycle, escalation risk needs visible control rather than a hidden cushion |
| Are owner decisions still open? | Freeze crop, technology, and phasing before release | If the design may still change, contingency will leak into rework instead of protecting the budget |
| Is the site package weak? | Hold a higher allowance until survey, drainage, and utility data are verified | If civil assumptions are provisional, site risk can dominate the budget even when equipment pricing looks firm |
- Blanket reserve vs split reserve: A single percentage is easy to approve, but it hides whether the problem is missing scope, time-based inflation, or site uncertainty. Split reserves take longer to set up, yet they make change control and finance review much clearer.
- Scope matrix: Check whether utility tie-ins, civil interfaces, controls, commissioning, and exclusions are written down. Missing scope belongs in the contingency bucket; known scope belongs in the base quote.
- Escalation timing: Compare quote validity, lead times, and tender timing. If the market window is the main issue, keep escalation separate so you can revise it without reopening the whole budget.
- Site evidence: Verify survey, drainage, and utility information before treating the quote as finance-ready. If the land package is weak, the allowance should stay higher until the gaps close.
For broader cost context, keep the commercial greenhouse cost framework in view while you normalize the budget inputs; for approval-stage assumptions and sensitivity testing, the greenhouse project budget framework is the better follow-up once the allowance is split. If you need a finance-stage check on downside exposure, the greenhouse investment guide helps frame the next decision.