I can think of several relatively simple methods to take a large building out of commission.
And don't think for a second that terrorists don't know about all of them and more.
I'm sure you could, as could I - drive up a truck filled with fertilizer comes to mind. But that's not the question being asked, just attacking a random large building - for example, a truck bomb wouldn't work for a chip fab, though, which is relatively dispersed and well-guarded, and alternatives like 'send over one bomber and drop one daisy cutter on the complex' aren't available to terrorists.
> And don't think for a second that terrorists don't know about all of them and more.
Please provide 3 examples of competent terrorists using your methods.