Board Thread:Warhammer 40k General Discussion/@comment-72.240.130.242-20130618172401/@comment-5165846-20130619122502

Shas'o'Kais wrote: The main point is that all Titans are relics. More than that, they are gods in their own right. The Cult Mechanicus would be outraged if someone suggested dismantling a god just because it's convenient. Although Tech-priests do replace arms and legs if they are damaged in battle, but that's maintenance and repair. Completely taking a Titan apart is another thing altogether.

Also, it's not convenient at all. The Priesthood of Mars does possess spaceships large enough to carry Titans by the dozen. Titans really are tiny compared to some space vessels. Given the cost and time required to assemble a Titan, as well as the heavy industrial equipment present on the Forge Worlds, it's just implausible and counterproductive. Not to mention that such a construction in a warzone can be risky, although the Mechanicum did build Titans on besieged Forge Worlds, notably on Mars during the Schism.

Finally, there are canon sources saying that the Titans arrive in one piece, and none (of which I'm aware, at least) saying that they are being disassembled. Some suggest that they need to be prepared, while others claim that they are fully operational from the start -- such as the mentioned Imperial Armour Volume VI, though it only covers the smaller Reaver-class Titans and Warhound-class Titans.