What is the world's largest building in volume......?

Answer 1

Largest volume = largest usable space

= The Palace of the Parliament in BucharestBoeing Plant in Everett, Washington, United States

At 13.3 million m³ (470 million cu ft), Boeing claims that its Everett Plant is the largest building in the world by volume. This claim is supported by the Guinness Book of Records. Originally, the plant encompassed 5.64 million m³ (200 million cu ft). The building is used to assemble the company's 747, 767, 777 and 787 aircraft..

Answer 2

Boeing's commercial-jet factory in Everett, WA. It is the world's most voluminous building-you could fit all of Disneyland plus five hectares of parking in it. And it's the birthplace of many of the world's largest commercial jets, including Boeing's 767, 777, and 747, the legendary 400-plus seat jumbo jet that has dominated much of long-distance air travel over the last three decades. One of the factory's doors is the size of a football field.

Answer 3

It used to be the Vehicle Assembly Building at Cape Canaveral in Florida, but now it's apparently the
Boeing Plant in Everett, Washington, United States

Still the VAB is impressive as a one story building.
http://en.wikipedia.org/wiki/Vehicle_Assembly_Building