Construction methodology defines how a project will be built; sequencing defines the order in which activities occur. Together they translate a design into a buildable, schedulable, and safe programme of work.
A poorly sequenced project drives cost and time overruns even when the design itself is sound: trades clash, plant sits idle, and rework compounds.
Developing a Construction Methodology
| Step | Purpose |
|---|---|
| Review design and site constraints | Access, geotechnical conditions, existing services, adjacent structures |
| Select construction methods | e.g. bottom-up vs top-down, precast vs in-situ, cut/fill strategy |
| Identify temporary works | Shoring, propping, formwork, falsework |
| Sequence major stages | Substructure → superstructure → envelope → fit-out |
| Assess plant and access | Crane reach, haul roads, laydown areas |
Work Breakdown Structure (WBS)
Projects are broken into a hierarchy of manageable work packages:
Project
├── Substructure
│ ├── Earthworks
│ ├── Piling / Footings
│ └── Basement Structure
├── Superstructure
│ ├── Structural Frame
│ ├── Floor Slabs
│ └── Roof
├── Envelope
│ ├── Facade
│ └── Waterproofing
└── Fit-out
├── Services
└── Finishes
Critical Path Method (CPM)
The critical path is the longest sequence of dependent activities determining minimum project duration. Any delay on the critical path delays the whole project; activities off the critical path have float (spare time).
$$ \text{Total Float} = \text{Late Finish} - \text{Early Finish} $$| Activity Relationship | Description |
|---|---|
| Finish-to-Start (FS) | Successor cannot start until predecessor finishes (most common) |
| Start-to-Start (SS) | Successor can start once predecessor starts (with a lag) |
| Finish-to-Finish (FF) | Successor must finish no earlier than predecessor |
| Lag/Lead | Time offset applied to a relationship |
Common Sequencing Strategies
| Strategy | When Used |
|---|---|
| Top-down construction | Congested urban sites, deep basements under existing structures |
| Bottom-up construction | Standard greenfield or open sites |
| Zone/area splitting | Large footprints: parallel crews working different zones |
| Vertical (floor-by-floor) repetition | Multi-storey buildings: cyclic trade sequencing per floor |
Temporary Works Coordination
Sequencing must explicitly account for temporary works and their removal:
- Shoring and excavation support (see Braced Cuts)
- Formwork and falsework strike times (concrete strength gain)
- Propping removal sequence and back-propping requirements
- Crane erection, climbing, and dismantling logistics
Programme Risk and Buffering
| Risk | Mitigation in Sequencing |
|---|---|
| Weather-sensitive activities (earthworks, roofing) | Schedule in favourable season, build in float |
| Long-lead items (precast, structural steel) | Order early, sequence around delivery dates |
| Interface risk (multiple trades/subcontractors) | Clear handover points, buffer float at interfaces |
| Concrete curing/strength gain | Sequence backpropping and loading around strength curves |
Practical Notes
- Sequencing decisions made at tender stage (e.g. precast vs in-situ) often lock in the entire programme logic: revisit them early, not after award.
- The critical path shifts as work proceeds; re-baseline the programme regularly rather than tracking against a fixed original schedule.
- Interfaces between trades and packages are where the most schedule risk concentrates: plan handover points explicitly, don't assume trades will self-coordinate.