Learn · Scheduling 101
Activities, durations and milestones: what a schedule is made of
After this subject you can say what an activity is, size one so somebody can answer for it, estimate how long it takes without burying a cushion in the number, and tell a milestone from a piece of work.
The pieces a schedule is built from
An activity is one piece of work the schedule tracks — the unit the whole thing is built from. Pour the slab. Set the steel. Order the switchgear. Each one is something the job has to get done, and a model of the work is made out of them.
How big should one of them be?
A size that works is one somebody can be held to. On most jobs "level three" is too big to answer for, and "set one anchor bolt" is too small to track separately. Many land between a day and a couple of weeks, though procurement and commissioning run far longer. If nobody can say who answers for one, settle that before the dates.
Why it matters — the size you pick decides who can honestly answer for it every morning.
How long it takes, and what that number is about
A duration is how long a piece of work takes once it is under way. The grid puts the common case in its own words: the amount of time an activity takes when crews are on it. Some work takes time with nobody on it — concrete cures whether or not anyone is there. Which DAYS it lands on is the next lesson.
Why it matters — the number usually comes from the quantity, the crew and the method, and sometimes from a delivery date or an approval you do not control. An unexplained cushion inside it is a decision nobody wrote down.
The one that takes no time at all
A milestone is a marker rather than work: a moment the schedule names, with no time of its own. Permit received. Substantial completion. Nobody works on a milestone — it is a point the work around it is measured against, and it is how a date that matters outside the crew gets a name.
Naming them well is most of the work
Names are a large part of whether a schedule can be read. "Slab" tells a superintendent nothing on a job with nine of them; "Pour slab — level 3 east" tells them where to stand. The grid's own help puts it in five words: an activity name is what the crew is doing.
Sizing one, in the trailer
Ask
Who owns this piece the whole way through?
Instead of
Which trade is on level three?
Ask
How long does this take once it is under way?
Instead of
When do we need this by?
Ask
What exactly are we calling done?
Instead of
Is it nearly there?
What to remember
- An activity is one piece of work the schedule tracks — the unit the whole thing is built from.
- Size one so somebody can be held to it.
- A duration is how long the work takes once it is under way, and not a statement about which days it lands on.
- A milestone takes no time; it is a moment the schedule names.
- Name them so a superintendent knows where to stand.
Name ten pieces of one week's work
Open a project and write down ten activities for a single week — what is being done, and how long each one takes once it is under way. Leave the dates alone for now; the lessons after this one build up to where the dates come from. If you would rather do it with somebody, bring one week of your own plan to a demo.