Every delay treated as equal
A site meeting spends twenty minutes on the landscaping start and two on the lift installation that is holding the whole building. Without float in view, the loudest delay wins.
Programme
Critical path in a construction programme: the activities with no float
Every construction programme has a chain of activities that sets the completion date. Delay any one of them by a day and the finish moves by a day; the others have room to slip. That chain is the critical path, and knowing which activities are on it is what lets a planner spend attention where a lost day costs a day. This page explains the idea with a small example and shows how Fidrel highlights the path in the Gantt.
30 days free · No minimum term.
Why the critical path gets lost in practice
A path that moved when nobody was looking
The path changes as progress is entered. The cladding was critical in March; after a late steel delivery the mechanical first fix is. A printed programme from February still shows the old path.
The cause of a hold-up is somewhere else
The activity is critical and stopped, but the reason is an unanswered query about a lintel, or an issue with access, sitting in another register. The programme has to point to it.
What the critical path is
Take a programme of linked activities. Working backwards from the forecast finish, each activity has a latest start: the last day it could begin without pushing the finish. Compare that with its planned start. The difference is its total float, the working days it can slip for free. Activities whose float is zero form the critical path, because any delay to them is a delay to the end. Float is not a property of an activity alone; it comes from the links, the durations and the calendar together, which is why the path changes when any of them change.
Scheduling
A worked example
Six activities for a small extension. Excavate, five days. Foundations, five days, after excavation. Drainage, three days, after excavation. Blockwork, ten days, after foundations. Roof, five days, after blockwork. Services first fix, four days, after blockwork and drainage. The finish is set by excavate, foundations, blockwork and roof: twenty-five working days, and none of those four can slip. Drainage has float: it can start up to seven days late and still be done before services first fix needs it. Services first fix itself finishes a day before the roof, so it has one day of float. If drainage overruns by eight days, it becomes critical and the roof does not.
Seeing the critical path in Fidrel
Step 1
Link the activities
In the programme give each activity its Predecessor under Dependencies, with the Type of link and a Lag in working days. Successors move forward automatically when dependencies require it, and the working calendar decides which days count.
Step 2
Switch on Critical path
Tick Critical path in the view controls. The activities with no float are drawn in a distinct colour in the Gantt, and the quick filter Critical lists only those activities so the table shows the chain on its own.
Step 3
Enter progress and watch the path move
Progress is entered directly in the chart. The path is worked out from the plan as it stands, with actual starts and finishes, so a late activity can pull a different chain onto the path.
Step 4
Mark what is blocking an activity
Under Linked records attach the RFI or the issue that is holding the work and tick Blocked. While that record is open the activity is shown as Blocked, and the key figures count the blockers in the programme.
How Fidrel works it out and shows it
Fidrel runs the reverse pass on the actual, constrained plan: activities that have begun keep their actual start, links with their lag in working days hold each successor, and the working calendar with its non-working dates decides what a day is. Zero total float marks the activities that control the forecast finish, including an activity with no successors whose own finish is the latest. With Critical path ticked those activities are coloured in the Gantt, the quick filter lists them, and a baseline can be shown beside them to see how far the chain has moved. Only the project’s administrators edit the programme; others read it.
Blocked activities and the cause of a hold-up
An activity on the path that has stopped needs a reason. In Fidrel an activity can be linked to records in the project, among them RFIs and issues, and a link can be ticked as blocking. While the RFI is unanswered or the issue open, the activity shows as Blocked, and the programme’s key figures count the blockers alongside milestones, days remaining and whether the plan is on schedule or needs follow-up. When the query is answered the block clears on its own. That makes the programme the place where the cause of a critical delay is read, rather than a list of dates beside a separate register.
What Fidrel does not do with the critical path
Fidrel shows which activities are critical, not the float of each activity in days; near-critical activities are not highlighted. There is no resource levelling, so float is calculated from links and the calendar only, not from gangs or plant. Asta Powerproject and Primavera P6 files are not read. Fidrel does not write a delay analysis or an extension of time: it shows the path as the plan stands today.
Related solutions
One project. One subscription. The entire platform included.
Your trial applies to your first own project and starts when that project is created. No card required. Afterwards, choose card or invoice to continue.
- 30 days free
- Unlimited participants
- No minimum term
Insights
View all
Project coordination just got simpler
The project system of the future connects people, documents and decisions. Discover the thinking behind Fidrel.
Read more
Your drawing, on site. Open DWG on your phone.
On site, answers need to be close at hand. Fidrel displays DWG drawings in your mobile browser, within the project’s document structure.
Read more
A clearer programme. From the first activity to the final milestone.
When everyone can see the next step, moving the project forward becomes easier. Fidrel brings activities, dates and reported progress together in a shared Gantt view.
Read more
The chain of linked activities with no float, from start to finish. Any delay to an activity on it delays completion by the same amount, while activities off the path can slip within their float.
The number of working days an activity can start late without moving the forecast finish. It comes from the links, the durations and the calendar together, so it changes as the plan changes.
Yes. As progress and actual dates are entered, an activity that overruns its float becomes critical and another may drop off the path. Fidrel works it out from the plan as it stands.
Yes. Two chains that both end on the finish date with no float are both critical, and Fidrel highlights every activity with zero float, whichever chain it belongs to.
Link the RFI or the issue to the activity under Linked records and tick Blocked. The activity shows as Blocked while the record is open, and the key figures count the blockers.
No. It highlights the critical activities and lists them with a filter. The float of an individual activity in days is not shown.