Quote:
Originally Posted by ketanco
In construction industry it is often not wanted to put negative lags between activities such as
(Predecessor Activity) FS - x days
I can understand that, as this means we are depending our link on something in the future and has not happened yet so it is not recommended.
Instead, it is suggested to use
(Predecessor Activity) SS + y days
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Actually, your original assertions are not correct in all cases. I often need to put lead times on activities, such as procurement, and this requires a ss- y days. The procurement period MUST happen before the desired event can occur, but its latest start date is determined by the projected start date of the activity. It is possible this will change, but I tend to put additional time in the lead period, which is generally a judgement call on how much variation is likely to occur.
As far as links depending on something in the future goes, this pretty much describes a programme. Planners predict the future, as best they can, and generally a good one will get it correct enough, but the unforeseen can and will occur.
/Using a baseline milestone (and I may have read this wrong)- you want to put a milestone in, and then use that as the basis for the activities that follow to negate a negative lag? This requires the milestone to be in advance of ALL activities, and the only way I can see to put this in with any accuracy is to put a negative lag on this activity, which defeats the purpose. A static milestone would give the problem that it does not move relative to other events, and you would need to move it manually, which defeats the purpose of a good programme.
As Julie says, a programme is live for the duration of a project, and you need to see what is happening (or trending) to be able to react positively with it. If tasks are slipping, you need to determine why - over optimism in planning, contractor not performing, unforeseen difficulties? A good planner will look for the cause of the problem and look for solutions- be it revising estimates of time and labour, replanning around obstacles, or simply kicking a contractor into picking up the pace.
How you plan your work is less pertinent than whether or not it works. I find that clients oftem insist on no negative lags, not because of any sound planning basis, but because they have an interrogative system that doesnt like it. "Good practice" is a phrase often used to justify a way of doing it for the sake of things, not because it has a soud basis.