Best Practice for SS or FS Relationship

This is against Bottom Up Planning by Mike Testro.

But For Discussion only, What we are using in our projects:

1. SS with FF combination

2. linking start milestone to finish milestone
can be used for delivery/equipment just on time arrivals.

3. lags must not be greater than half the duration of activity.

4. within 14-21 days, usually 15

5. maybe below 60-75

Good Day Aryan,

My answers yo your questions are below:

1. Which one is beneficiary for planning, Finish to Start with negative lag or Start to Start with positive lag?

We try to avoid negative lags. SS links are used in combination with FF links most of the times.

2. Start to Finish relationship can be used in what circumstances?

Very rarely, usually on hammock activities. An example: project management (hammock) is finished when the results were accepted.

3. What about Lags longer than zero?

We prefer to use not time but volume lags. Lags are usually positive.

4. Considering Near critical path activities, how many days can we consider that the activity to be near critical?

Depends on project duration and risks involved

5. Considering Total float how many days can we consider to be acceptable? (e.g. 10, 50, 100.....or more than...)

Shall be calculated basing on project risks and uncertainties.

Regards,
Vladimir

Regards,

Aryan

Hi Aryan

(Thanks Solo and Vladimir - you knew that I could not keep my nose out of this one)

SS FF Links with lead lags are ok if you are preparing a very broad top down programme.

You have to be very experienced in the type of project to accurately estimate the postion of the lead lag link.

The method is OK in level 1 & 2 programmes but not in levels 4 & 3 where Bottom up Method is the most accurate way of generating a critical path.

Have a look at some of the earlier bottom up threads on PP and let me know what you think.

Best regards

Mike Testro

SS & FF between two activities known as “laddering” cannot be handled well by some programs. The following link provides you with an example of this issue.
http://www.mosaicprojects.com.au/PDF/Links_Lags_Ladders.pdf

If you have P3 you can run Figure 11 schedule, run it once with the Tools/Schedule/Options/Contiguous Schedule Durations and then with Tools/Schedule/Options/Interruptible Schedule Durations.

SureTrak (this is what I use) could not handle the issue as well as P3. For your software you will have to figure it out.

I run a 531 calendars day baseline schedule I created in Suretrak for an actual job, with ladders occurring very often. I got a difference of 5 days when run it under P3 and applied P3 option for activities can split. Of course SureTrack mishandling was always on the safe side, what a big deal.

Beware of this trap if your software cannot handle it or if it can, then make sure you got the appropriate settings.

For your enjoyment apply the Bottom up Method to the example, where to split is well defined. No big deal, only one occurrence.

Hi Guys,

Thank you so much for your help.

I will try to use your suggestion. However if you don’t mind, can you recommend me some links or reading materials regarding the best practice for planning with regards to my main issues.

Thanks again.

With best regards,

Aryan

Aryan:

Please when you read best practice make your own judgment, some go overboard and pretend you do not use some advance PDM features such as “lag”, others more open minded recognize the need for them but warns about its misuse.

I am on the open minded side; this will be a never ending issue. Even some American Gurus at a time were against the “new” PDM features, now I have seen them retracting.

One thing we all agree, there is the need for “Good Practice” guidance, but some of us believe; guidance not absolute rules to be always followed as if written in stone.

Scheduling is not an exact science, think of it as a sport, a coach will guide you under the knowledge of best practice but will adapt to your particular needs. Take for example baseball, no matter what, 3 strikes is an out, but how you step at the plate and what is your best swing will vary, no rule will tell you exactly how to swing the bat. The coach will do adjustments to your swing but will not ask you to change it.

The purpose of my last posting about doing Bottom Up to a single occurrence was to illustrate the extra effort I consider unnecessary, imagine this hundreds of times with multiple cross dependencies. Contractors have their particular way of thinking and organizing their jobs, forcing them to follow what for them is unnatural is wrong.

In case you note what at first glance might look to be my contradictory arguments, I do it on purpose, to fire up the debate.

This will be a never ending debate until these stubborn Gurus that created the confrontation rest in peace, only then CPM will be back to where it belongs, to the Project Manager and his Planner/Scheduler and finally so much confrontation will be a thing of the past.

Sorry I cannot provide you with a reference on Best Practice, I have not found any that satisfy my standards, yet, none. I follow some practices and others I don’t even pay attention. But yes I often read them, always something good comes out.

Best regards,
Rafael