I have tasks set to fixed duration which means I can change the work hours independently. However, when I change the duration it changes the work hours. Can I stop this?
If you have resources already loaded against a package that has a duration value and a work value, then when you change duration, it will adjust work based on the assumption that the resources loaded do not change their utilization level. If you want to alter the duration, then you need to type in the work value again; that will adjust the resource(s) utilization accordingly.
The default logic in the tool for fixed duration is for it to automatically adjust work, then resources, in that order.
If you do not have resources loaded, and you play around with duration, the work will NOT change, because there is no third variable against which to change the work value.
I do not know if you can change the logic in the tool.
First: Double click on the task name (not on the Gantt bar!) -> Advanced -> Task Type -> set "Fixed Work".
Then: Now you can add resources or change the duration without changing the "Work" hours or days.
You may want to add the column "Work" to the task grid in order to verify that this works.
These two values can not be worked on independently. If the the duration, is fixed, the hour worked will be adjusted as the duration changes. If my task is wait for Monday, and you change the duration to end on Friday, I now have four more task days.
If duration is not fixed, then start date will move when a fixed end date is moved. If my task is wait four days, then I will start Monday if the end date is Friday.
Normally, I would set a milestone, and use effort constrained tasks.
Depending on the software you may be able to level fixed effort with a fixed start date, when you move the end date. This may allow you to setup unreasonable schedules.
Actually if you click on each task, in tab "Advanced", set "Task Type" as "fixed Duration", it will make things much easier.
so when you structure your project plan, you can decide on duration of each task, then the Work (effective hours required for each task), then put in resource. that way, the resource effort in % will be automatically adjusted, without having either Duration or Work changed.
hope this helps. I've tried it.