Key takeaways
- The S-curve tells you when the money goes out; the BOQ tells you where it goes. You need both together.
- The sample 24-month plan has a peak monthly drawdown of 7.5% of the construction budget, 1.8 times the monthly average of 4.17%.
- The parallel 3-building mid-rise plan takes 27 months of construction according to the programme, and a buffer should be allowed to bring it into a 28–32 month range.
- Cash flow must be separated from work progress, because retention, lift milestones and advance payments mean that cash goes out out of step with the percentage of work completed.
The S-curve is not an average
Using a simple average of 100% ÷ 24 months gives 4.17% a month. Real work, however, starts slowly, accelerates when the structure and building services overlap, and then slows towards the end. This difference is why projects often run short of cash mid-way, even when the total loan amount is sufficient.
Reference range for a 24-month project
| Stage | Stage | Cumulative % | Nature of work |
|---|---|---|---|
| Phase 1 | M1–M4 | 5–10 | Mobilisation, piling and foundations; the curve is still flat |
| Phase 2 | M5–M12 | 40–45 | Structure rising floor by floor continuously; speed increases from about 0.7% to 1.4% per week |
| Phase 3 | M13–M20 | 85–90 | Architectural and MEP works overlap; peak of about 1.7% per week in months 14–15 |
| Phase 4 | M21–M24 | 100 | Testing, snagging, FF&E, handover and closing the final account |
Sample monthly drawdown plan, hard cost THB 500 million
| Month | Monthly % | Cumulative % | Drawn this month (THB million) |
|---|---|---|---|
| M1 | 1.0 | 1.0 | 5.0 |
| M2 | 1.5 | 2.5 | 7.5 |
| M3 | 2.5 | 5.0 | 12.5 |
| M4 | 2.5 | 7.5 | 12.5 |
| M5 | 3.0 | 10.5 | 15.0 |
| M6 | 3.5 | 14.0 | 17.5 |
| M7 | 4.0 | 18.0 | 20.0 |
| M8 | 4.5 | 22.5 | 22.5 |
| M9 | 5.0 | 27.5 | 25.0 |
| M10 | 5.5 | 33.0 | 27.5 |
| M11 | 6.0 | 39.0 | 30.0 |
| M12 | 6.0 | 45.0 | 30.0 |
| M13 | 7.0 | 52.0 | 35.0 |
| M14 | 7.5 | 59.5 | 37.5 |
| M15 | 7.5 | 67.0 | 37.5 |
| M16 | 6.5 | 73.5 | 32.5 |
| M17 | 5.5 | 79.0 | 27.5 |
| M18 | 4.5 | 83.5 | 22.5 |
| M19 | 3.5 | 87.0 | 17.5 |
| M20 | 3.0 | 90.0 | 15.0 |
| M21 | 2.5 | 92.5 | 12.5 |
| M22 | 2.0 | 94.5 | 10.0 |
| M23 | 2.0 | 96.5 | 10.0 |
| M24 | 3.5 | 100.0 | 17.5 |
Month 12 is at 45% cumulative and month 20 at 90%, which is at the upper edge of the reference range. The final month's figure is slightly higher than the previous month because it usually includes contract close-out work.
Reading the example
The monthly average is 500 ÷ 24 = THB 20.8 million, but the peak month is THB 37.5 million, which is THB 16.7 million above the average. If cash is planned using the average, the team will see enough facility overall but will run short of cash in months 13–16.
3-building mid-rise programme, 210 units
This example is a 3-building mid-rise condominium built simultaneously. The total period from project start to handover is about 44 months, excluding the warranty period.
Before construction
| Task | Period | Month | Outcome |
|---|---|---|---|
| Feasibility and market research | M1–M3 | 3 | Approved feasibility report |
| Land purchase and due diligence | M1–M4 | 4 | Land ownership transfer |
| Concept and schematic design | M3–M7 | 5 | Design approval by the project owner |
| EIA | M4–M12 | 9 | EIA approval |
| Detailed Design | M6–M12 | 7 | Complete construction drawings |
| Building permit and utilities approvals | M10–M14 | 5 | Building permit |
| Tender and contractor selection | M12–M14 | 3 | Main contractor contract signed |
The EIA threshold for multi-unit residential buildings is based on project size: 80 or more rooms, or a usable area of 4,000 sq m or more. It is not based on the number of storeys. This 210-unit project therefore meets the EIA threshold and should be treated as a critical path item, as it could be delayed by 6–12 months.
Construction works: cost weightings totalling 100%
| Code | Task | Period | Month | % of construction budget |
|---|---|---|---|---|
| 2.1 | Site preparation and mobilisation | M14–M16 | 3 | 2.1 |
| 2.2 | Piling for 3 buildings | M15–M18 | 4 | 8.2 |
| 2.3 | Substructure and basement | M17–M21 | 5 | 9.3 |
| 2.4 | Superstructure for 3 buildings | M19–M30 | 12 | 31.0 |
| 2.5 | Architecture, external walls, doors and windows | M24–M36 | 13 | 20.6 |
| 2.6 | MEP | M22–M36 | 15 | 13.4 |
| 3.1 | Fit-out of 210 units | M28–M38 | 11 | 8.2 |
| 3.2 | Common Area Fit-out | M30–M38 | 9 | 4.1 |
| 3.3 | Landscape and hardscape | M32–M40 | 9 | 2.6 |
| 3.4 | Final testing and commissioning | M38–M40 | 3 | 0.5 |
| Total | 100.0 |
If each work item is spread evenly over its duration, cumulative progress is about 44% at M25, 72% at M30, 96% at M36 and 100% at M40. The peak month is around M30 at 6.3% per month, which is 1.7 times the average of 3.7% per month. This pattern is consistent with the reference range, but the peak will fall in the months when structural and building services works overlap the most.
Critical path check
- The EIA must be completed before a building permit can be applied for. Allow a buffer.
- Building 3 towers simultaneously requires 3 tower cranes and clearly divided teams.
- Lifts, chillers and sanitary ware should be ordered at least 6 months in advance.
- The structure-rising phase suits sales, because customers can see progress.
- Apply for the Or. 6 (building completion certificate) and register the condominium before the scheduled transfer day.
Converting progress into cash
The figures in the table above are certified work value, not cash. Before entering them in the cash flow, adjust for the following items.
| Item | Effect on cash |
|---|---|
| Contractor advance payment | Cash goes out before the work, then is deducted back progressively in instalments |
| Retention | Cash goes out after the work, with retention released on handover and at the end of the DLP (defects liability period) |
| Lifts and specialist works | Paid by milestone, not by percentage of work completed |
| Credit period | Cash goes out after the certification date, according to the contract terms |
| Irrecoverable VAT | Increases cash paid out and increases cost |
Example: 5% retention on a THB 500 million contract
At month 12, cumulative progress is 45%, or THB 225 million. Cumulative retention is THB 11.25 million, and the payment before VAT is THB 213.75 million. At the end of the works, the project owner holds THB 25 million of retention. If 50% is returned on handover and 50% at the end of the DLP, THB 12.5 million must be set aside twice, and these sums often fall in the period when the project is recognising revenue from transfers.
Disbursement plan checklist
- Use a monthly plan based on the contractor's actual programme
- Separate certified work value from cash paid
- Compare against the loan facility, the availability period and the drawdown conditions
- Check that the peak month is covered by facility headroom or presale inflow
- Keep the baseline S-curve to compare against actual progress every month, and explain any month that falls outside the reference range