Siege machines
Built in the field by your troops (all but the Trebuchet) and crewed by them.
Field Infirmary A healing tub on wheels for after a battle. Once no enemy is in sight, wounded troops take turns lying in it and heal fast while its doses last. A dose is 1 extract and 2 berries. Its crew only moves it. Only warriors can build it. 
Field Ladder Lets your warriors and carters climb a one-level step. Only warriors can build it. 
Field Ramp A long timber ramp up a one-level step for warriors, carters and siege machines. Only warriors can build it. 
Battering Ram Batters the wall, gate or dam in front of it, faster with more warriors aboard. Only warriors can build it. 
Siege Tower Rolls up to a wall and lets the warriors aboard out onto its walk. Only warriors can build it. 
Catapult Hurls stones at a chosen target, hurting enemies and battering walls and siege engines. Its crew moves and aims it. Only warriors can build it. 
Ballista Shoots heavy bolts flat and far: deadly to enemies, weak against walls. Its crew moves and aims it. Only warriors can build it. 
Trebuchet Hurls siege stones at a chosen target, hurting enemies and battering walls, gates and siege engines. Needs warriors aboard to turn and throw.