for building to building connectivity on P2P - line of sight (LOS) is needed...
however do u have any other building in between your buildings under your control or with friendly terms bcos if you do then you can do P2P dog legging...again you need LOS even then...
Dog legging is when both ends of the link have not got line of sight to each other, but both have line
of sight to a common point. This common point can be used as an
intermediate point or "dog leg". The most efficient way to use this
point is to have 2 separate wireless bridges (4 radios total) as there
is no loss of throughput. It is possible also to create a dog leg by
having the intermediate point repeat the signal however this will half
the links throughput as the central radio has to spend half its time
listening to signals sent to it, and the other repeating them.
just rough diagram below
Your Building 1 (P2P-1) ----------------LOS---------- (P2P-1) Friendly building (P2P-2)------------LOS---------- (P2P-2) Your building 2
there are many things one can do like above, meshing, point to Multi point, P2P daisy chaining...
all depends on how important this is and what all things u have under control and where...
best of luck...