When a resource is over allocated why does the "extend duration of task" option sometimes not appear?

Question

I am pretty green and I am having an issue. I have 2 staff that can commit 50% of their time to the project. I opened the resource sheet and set their units to 50%. Then when I assign someone to a large task, maybe 15 hours, it shows they are over allocated. Sometimes it gives me the option to extend the duration and sometimes it does not. What are the conditions that make the system give that option? Can I force it to extend the duration?

The business case is this. The staff will be writing a piece of software, lets say the search functionality will take 20 hours to complete, I want to see how long it will take if the resource has 50% availability.

If anyone can point me in the right direction that would help a lot!

Answer 1

Have you looked at how many units are allocated for the resource inside the task ? Double click on task and look the resources tab. There should be 100%, change it to 50%.

Also what is your schedule option? Fixed Units or Fixed work. If you have 20 hrs estimate, it seems you should use Fixed Work scheduling approach. This can be found in project properties.