Scheduling and delivery

22 terms in scheduling and delivery

Construction programme

The construction programme, or schedule, is the planned sequence and timing of the work on a job, built from tasks, durations and the dependencies between them. A programme whose tasks are not genuinely linked recalculates nothing when one of them moves, which is why most schedules die. Scheduling reference. See also: Dependency, Baseline.

Dependency (scheduling)

A dependency is a genuine constraint that one task cannot proceed until another reaches a defined state, most commonly finish-to-start. Real dependencies are what let a schedule recalculate when something moves; decorative links drawn to make the chart look connected do nothing. Critical path reference. See also: Critical path.

Critical path

The critical path is the longest chain of dependent tasks through a programme, the chain on which a one-day slip is a one-day-later handover. Tasks off the path carry float; tasks on it carry the completion date. Critical path reference. See also: Float.

Float

Float is the amount a task can slip without delaying the completion date. It quietly disappears as other tasks consume it, and a task whose float reaches zero has joined the critical path whether anyone noticed or not. Critical path reference. See also: Critical path.

Baseline (scheduling)

A baseline is the approved version of the programme held fixed so the current plan can be measured against it, two dates per task, planned and current. Without a baseline, drift is invisible and every reforecast quietly rewrites history. Baseline and progress tracking reference.

Milestone

A milestone is a zero-duration point in the programme marking a defined event, a stage completion, an inspection or an approval. Milestones are what claims, inspections and client communication anchor to, which makes them the most watched dates on the job. Scheduling reference.

Lead time

Lead time is the period between ordering something and its availability on site. It is the hidden dependency behind every start date, because a task cannot start before its materials arrive no matter what the programme says. Lead times reference. See also: Long-lead item.

Long-lead item

A long-lead item is a product whose lead time is long enough to drive the programme, commonly windows, trusses, kitchens, switchboards and made-to-order products. Long-lead packages are ordered off the programme weeks or months before they are needed, or the programme moves to suit them. Lead times reference.

Need-on-site date

The need-on-site date is the date the programme says a material or product must be available for the work to proceed. Order dates are derived backwards from it, need-on-site less lead time less a buffer, which is the arithmetic the call-forward schedule exists to hold. Procurement and schedule alignment reference. See also: Call-forward schedule.

Trade stacking

Trade stacking is compressing the programme by putting multiple trades in the same space at the same time. It reads as acceleration and usually delivers rework, damage and slower overall progress, which is why it is a false economy rather than a schedule recovery technique. Lead times reference.

Gantt chart

A Gantt chart is the bar-chart view of a programme, each task a bar along a timeline with its dependencies drawn between them. It is how most builders read a schedule, and its usefulness depends entirely on whether the bars are genuinely linked underneath or just drawn side by side. Scheduling reference. See also: Construction programme.

Look-ahead schedule

A look-ahead schedule is a short extract of the programme, commonly the next two or three weeks, used to coordinate trades, deliveries and inspections in the near term. It is the working tool that turns the master programme into what happens on site this fortnight, and it is where slippage is caught early enough to act on. Baseline and progress tracking reference. See also: Construction programme.

Predecessor and successor

A predecessor is a task that must reach a defined state before another can proceed, and the successor is the task that depends on it. Naming the predecessor and successor correctly is what gives a dependency its meaning, so the programme recalculates properly when either one moves. Critical path reference. See also: Dependency.

Finish-to-start(FS)

Finish-to-start is the most common dependency type, where a task cannot start until its predecessor finishes, such as plastering waiting on rough-in. Other relationships exist, start-to-start, finish-to-finish and start-to-finish, and using the right one is what stops a schedule linking tasks in a way the site cannot actually follow. Critical path reference. See also: Dependency.

Lag

Lag is a deliberate delay built into a dependency, such as waiting for concrete to cure before loading it, so the successor starts a set time after the predecessor rather than immediately. Modelling curing and drying as lag is how a programme respects the physics of wet trades instead of pretending the next task can start straight away. Critical path reference. See also: Wet trades.

Acceleration

Acceleration is compressing a programme to finish sooner or to recover lost time, by adding resources, working longer or overlapping tasks. It carries real cost and risk, and pushed too far it becomes trade stacking, which usually delivers rework rather than genuine speed. Lead times reference. See also: Trade stacking.

Recovery programme

A recovery programme is a revised plan for pulling a slipped job back toward its completion date, showing the specific changes in sequence, resources or scope that will do it. A credible recovery programme is measured against the baseline, so everyone can see what is being made up and how. Baseline and progress tracking reference. See also: Baseline.

As-built programme

An as-built programme records when tasks actually started and finished, as opposed to when they were planned. Read against the baseline, it is the evidence behind a delay claim or an extension of time, showing what really happened rather than what was intended. Baseline and progress tracking reference. See also: Baseline.

Weather delay

A weather delay is lost time caused by inclement weather and its after-effects, such as a site too wet to work. Whether it entitles the builder to an extension of time depends on the contract, and a contemporaneous record of the days lost and their cause is what supports the claim. Extensions of time reference. See also: Extension of time.

Programme slippage

Programme slippage is the drift of tasks later than their planned dates, task by task, until the completion date moves. It is invisible without a baseline to measure against, and catching it while float still absorbs it is the difference between a note and a delay. Baseline and progress tracking reference. See also: Float.

Trade sequencing

Trade sequencing is the order in which trades come onto a job so each has what it needs and none undoes another’s work. Good sequencing keeps trades out of each other’s way and respects the drying and curing the wet trades need, which is the opposite of stacking them into the same space. Lead times reference. See also: Trade stacking.

Schedule buffer

A schedule buffer is deliberate slack placed before a critical date or a long-lead delivery to absorb the normal variability of a job. It is planned protection rather than the accidental float that other tasks leave behind, and it is what keeps an order-by date or a handover realistic when small delays accumulate. Procurement and schedule alignment reference. See also: Need-on-site date.