Art - Ground texture in the Object Editor. Check Farm's ground texture and adjust.
Then, edit Pathing Map and add the one you desire. (Farm's can be built close to each other while Barracks further away)
Remember to also alter Scaling value, Collision size and Selection scale if you want a smooth-looking building.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.