(+)
Friendly buildings (including friendy sappers!) can be healed as well as your teammates
Can collect uber from healing buildings!
(-)
-15% ubercharge rate if you are healing buildings
-75% max overheal for buildings
-50% ubercharge duration

Ubercharge is divided into 4 stacks.
Ubercharge removes sapper from building and gives:
To Sentry Guns: +50% damage resistance and +20% faster firing speed
To Dispensers: +50% damage resistance and +200% dispencer range and healing rate
To Teleporters: +50% damage resistance and +200% faster recharge rate
To Sappers: use the ubercharge on the sapped enemy building to instantly destroy it!
To Players: +50% damage resistance and immunity to headshots and backstabs