Microsoft Project - Tasks - Lead and Lag Times

Lead and Lag Times 

hen planning a project, it is broken down into the component parts and then linked depending on how the tasks follow on from one another.   When the links are entered it does not allow for waiting time of any kind.  For instance when painting a room the top coat is done after the undercoat - but it can not be done immediately afterwards as the undercoat has to dry first.  The gap in time between the first task stopping and the second task starting is the lag time.   

The lag time is associated with the link between two tasks.  It can be entered as a fixed duration or it can be entered as a percentage of the predecessor task.  

When entering a lag it will take the calendar into consideration so that if there is any non working time on the standard calendar this will be taken into consideration.    

These tasks have a two day lag (2d) between them.  The two days being used as the lag days are Friday and Monday.   

This depends on whether the delay required needs to take into consideration when people are working.   

If some information is requested from a different organisation and they need to generate it from a source of some kind - then the weekend needs to be taken into consideration as to when that information is available. 

If the lag requires a 48 hour fixed gap between the two tasks for instance if paint is drying or tarmac is setting then the weekend will be just as effective as a working day.  So that non working time is not taken into consideration the lag can be entered as an elapsed time value. 

A lag of two elapsed days (2ed) - the two days of lag are Friday and Saturday.  Task 2 starts on the next working day. 

Any time lag (but not the percentage lag) can be changed to an elapsed time lag by preceding the time unit with the letter e.   

Durations entered in lag times will allow tasks to overrun into non working time but will not allow tasks to start in non working times 

The first task is finishing on Saturday as the duration is entered in elapsed time, but the second task is not starting on Sunday even though the task is entered in elapsed time.  

(Saturday and Sunday are non working times. 

Lag times will delay a task, however there are times when you want a task to start slightly earlier - this is known as a lead time.   

For instance if a room full of computers has to be disconnected and then packed - not all of the computers have to be disconnected before someone else is packing them up. 

A lead time is entered in the same way a lag time, it is entered at the same place but it is entered as a negative value. 

The lead and lag times can be entered against any of the four types of links - but do check the results to make sure they are what you want to happen. 

Setting the Lead and Lag Times 

Mouse 

Once the link has been established.  Double click on the link line.  The dialogue box below will appear on the screen 

In the lag box enter the value or percentage required.  Entry in the table - predecessors column 

After entering  the predecessor and the type of link enter the lag or lead time as a positive or negative value.