Can a grounded guy (the flash) move through hindering and on top of buildings using HSS?

no.

He still has to stop in hindering terrain and must use the stairs or a ladder to get on the building.

Here's a hss question that has sparked a continual discussion at our venue. Can you use exploit weakness in conjunction with hss? If so then I can't argue. If not, I was robbed!

no, you cannot, EW only works with charge, not HSS.

Exploit Weakness and Quake do not work with HSS.

Thanks T.T. Now the KC Shazam will feel the full wrath of the God of Thunder.

From the FAQ:

Exploit Weakness requires a close combat action

...so nope you can't use Exploit Weakness with HSS (the move option anyway, didn't check about option 2)

whoops looks like i was really late on that one (had to type stuff off the FAQ *P.O.S. .pdfs!*)

but anyway, there is the FAQ proof, if you wondered