Work Activity
A Work Activity represents physical, cost-loaded execution. It can use an S-curve, Linear distribution or Manual Work schedule. Work Activities contribute to project Work duration and can carry subcontract commercial terms.
Methodology
A forecast designed to be revised
CashflowPot is a construction cash-flow simulation model. It separates expected Work, direct Scheduled Cost, contract terms, forecasting assumptions and financing so each layer can be reviewed rather than hidden inside one result.
The purpose is not to claim permanent precision. It is to create a transparent financial view from the information available now and make it quick to revise when the project changes.
Purpose
Time-phased work or cost is not yet a commercial cash-flow forecast.
Detailed planning systems can provide programme logic and time-phased work or cost. CashflowPot focuses on the commercial and financing layers that follow: expected receipts, project payments and funding after contract terms, forecasting assumptions and financing facilities are applied.
A current programme can inform activity timing. A mathematical execution profile can also be used when detailed loading does not yet exist, would take disproportionate effort for the decision, or has become stale after repeated project changes.
Activity model
Work Activity and Scheduled Cost are deliberately different.
Scheduled Cost
Scheduled Cost represents direct project expenditure entered by period. It contributes to project cost, outflow and funding need, but creates no physical Work, no client PPC and no additional Work duration.
Manual Work replaces only the generated Work curve. The normal Work outflow pipeline still applies afterward, including direct/subcontracted split and subcontract timing.
Main-contract inflow
Two ways to generate the contract-value work curve
Independent contract curve — default
Work Activities establish the execution duration and project Work horizon, while contract value follows its own curve over that duration. Choose Linear or S-curve. For the S-curve, timing can be Back-loaded, Balanced or Front-loaded. New scenarios default to a balanced S-curve.
Activity-linked inflow — alternative
The combined Work Activity cost-work profile is scaled proportionally to contract value. Scheduled Cost is excluded from both the Work-cost denominator and the contract-value work profile.
Both methods preserve the same project contract value. Neither method assigns individual selling prices or a Schedule of Values to Activities.
Activity-linked detail
Only Work cost is used to scale Activity-linked inflow.
When Activity-linked inflow is selected, CashflowPot scales the combined Work profile to contract value.
Value factor = Contract value / Total Work Activity cost
Contract-value work(t) = Project Work profile(t) × Value factor
Scheduled Cost affects outflow and financing requirement but does not create billable client value.
Client side
Turn contract-value work into PPC and expected receipts.
The chosen contract-value curve is not yet cash received. CashflowPot next applies the relevant contract terms and forecasting assumptions.
- Advance payment and recovery — generally a contract term.
- Retention and release timing — generally contract terms.
- Payment period — the model periods between billing and receipt.
- Work in Excess of Billings (WIEB) — a forecasting assumption for the share of completed work not billed in the current period.
- Defects Liability Period (DLP) — the period between the first and remaining retention releases.
PPC timing
PPC issued and PPC receipts are not the same series.
PPC issued represents net progress-certificate value in the certificate period, before client payment delay. PPC receipts represent employer/client cash received after the configured payment timing.
This distinction matters for financing. A PPC Discount draw can be based on PPC issued, while a percent-of-PPC repayment can be based on PPC receipts.
WIEB
Performed work and billable work can occur in different periods.
Work may be incomplete, awaiting inspection or approval, affected by an NCR, or otherwise not yet ready for certification. CashflowPot uses the WIEB percentage as a forecasting assumption to carry part of each period's otherwise billable work into the next period.
Billed(t) = Work(t) × (1 − WIEB) + Work(t−1) × WIEB
WIEB changes timing, not lifetime value.
Work Activity outflow
Work cost can be self-performed or subcontracted.
Base Work profile
Generated Work uses an S-curve or Linear distribution. Manual Work uses the entered marginal schedule. Start and pre-work periods shift execution in time without changing total estimated Work cost.
Linear cumulative work(t) = Activity cost / Duration × t
Direct and subcontracted shares
Each period's Work cost is split between self-performed/direct Work and the subcontracted share.
Self-performed cost(t) = Work(t) × (1 − Subcontracted share)
Subcontracted work(t) = Work(t) × Subcontracted share
Direct cost is paid as incurred. Subcontracted Work follows its own advance, WIEB, no-billing period, retention, Payment period and DLP rules.
Scheduled Cost outflow
Some project costs should be placed directly in time.
For Scheduled Cost, the entered schedule is the outflow schedule. CashflowPot does not transform it using subcontract advance, retention, WIEB, DLP, payment delay or pre-work rules.
Scheduled Cost work(t) = 0
Scheduled Cost outflow(t) = Entered scheduled amount(t)
Scheduled Cost can extend the financial forecast after physical Work ends without extending Work duration.
Financing facilities
Financing sits on top of Project Cashflow.
A facility draw is financing cash received, not project revenue. Principal repayment, interest and fees are financing outflows.
- Scheduled draws
- PPC-linked draws
- Automatic-shortfall draws
- Cashflow sweep repayment
- Percent-of-PPC repayment
- Scheduled or equal-installment repayment
- Interest and fees
Facility capacity
Revolving and non-revolving facilities use different capacity rules.
Revolving
Available capacity is based on current outstanding principal. Repayment restores capacity that can be drawn again while the facility is available.
Non-revolving
Available capacity is based on cumulative actual draws. Repayment reduces outstanding principal but does not recreate draw capacity already used.
Cash position
Project Cashflow, Facilities and Cash Position remain separate.
The result is presented in layers so project economics are not confused with funding.
Total inflow = Project inflow + Facility draws
Total outflow = Project cost + Principal repayments + Interest + Fees
Net cash flow = Total inflow − Total outflow
Closing cash balance(t) = Previous closing balance + Net cash flow(t)
Facility Outstanding balance is a balance-sheet-style exposure, not an inflow or outflow row.
Decision metrics
Use KPIs that separate project need from financing structure.
Peak Funding Requirement
The magnitude of the most negative pre-financing cash balance, with the period in which it occurs.
Peak Facility Usage
The highest combined outstanding facility principal during the modeled horizon.
Outstanding Facilities
Facility principal still outstanding at the end of the modeled horizon.
Cash after Debt Settlement
Final Closing Cash less final outstanding facility principal. It is a principal-only settlement view and does not invent future interest outside the modeled horizon.
Time convention
Work duration and Financial horizon are different.
Work duration is derived only from Work Activity execution. Financial horizon can continue later because of Scheduled Cost, PPC timing, retention, DLP, subcontract payments, facility draws, repayments, interest or fees.
CashflowPot is normally used monthly, but the engine itself uses integer model periods. User-facing periods are shown as P1, P2 and so on.
Model invariants
Commercial conditions primarily change timing; the model keeps source totals explicit.
Σ Work Activity work = Work Activity estimated cost
Σ Work Activity outflow = Work Activity estimated cost
Σ Scheduled Cost work = 0
Σ Scheduled Cost outflow = Scheduled Cost total
Σ Project inflow = Contract value
Subject to valid inputs and normal numerical precision.
Legacy financing fallback
Explicit facilities are the current financing model.
When no explicit financing facilities are configured, CashflowPot retains a legacy scenario financing-rate fallback for compatibility. When facilities are configured, the facility engine calculates draws, repayments, interest, fees, funded cash balance and outstanding principal explicitly.
Model limits
Use the model to support a decision, not to manufacture certainty.
CashflowPot produces a forecast, not a guarantee of future receipts, payments or funding needs. Results depend on the project information, contract terms, facility terms and forecasting assumptions entered into the scenario.
The model does not calculate critical path, delay entitlement, detailed BOQ measurement, accounting statements or individual Activity selling values. When better information becomes available, update the scenario and compare the revised cash position.
Advanced: non-linear Work curve
The raw cumulative curve used by the current engine is:
C_raw(t) = c × (s + 1) / ((s + 1) + exp(−(t / (0.1d) + s² − 5)))
The engine corrects the residual so the resulting marginal Work returns to the Activity's estimated cost. Normal users only need to choose a curve and its timing shape.