"As late as necessary contraint"

Question

Hello,I have a big project with most tasks being dependent on a "Construction start" milestone. That whole structure is set up and works nicely. Now I have to add some land clearing work as "secondary tasks", they can be executed before the "Construction start"-milestone but they must not delay the main tasks. The land clearing work can only be performed in winter because of bird protection periods, I have set that up with a ressource. The result looks something like this:My problem is I want the land clearing work to be performed as late a necessary, not years in advance at the project start, but without delaying the end date. If I set the task to be scheduled "as late as possible" it moves everything else back and it overloads my resource aswell:Is there a way to fix this without setting manual Dates? The start dates are not yet fixed and I want as few fixed dates as possible so I dont have to manually adapt everything incase there's a change.

ignacio_martin · Answer

Hi MarkurzYou can try the Start to Finish (SF) link between Id=8 Construction start &nbsp;(Predecessor) and Id= 10 land clearing (Successor).You can even give the link lag time by entering a negative duration in the link Lag field.Example:&nbsp;Predecessor of task Id=10 (land clearing): 8SF-4 dI hope this helpsIgnacio

trevoratperfectproject · Answer

I definitely recommend do not use ALAP in this case, and reserve it for those very few rare circumstances where it is really useful or necessary (almost never).

You have seen how it works, and people usually think it means the same as zero free float (slack), which it is not. It sucks all of the total float (slack) out of all of the successors.

I also recommend not using weird links, like SF and lag, especially discourage negative lag.

Make that manually scheduled task auto scheduled.

Schedule everything, including the land clearing, ASAP which is a basic characteristic of Critical Path Method. Then you will know the early and late starts and finishes, free float and total float. See the schedule table. If you switch to the detail Gantt view you can see the total float on the bars in the chart.

Make a task calendar which restricts the available dates to the non bird protection periods, and assign that calendar to the land clearing.

Make a 7 days/week calendar and assign that to the recurring bird protection period.

Now you can choose any date between the earliest star and latest start as the intended date to start the land clearing.

Here is a picture.