You would need to build a tent like scaffolding that you can still work in, e.g. with a crane. That would be a non-trivial thing to design, put up and maintain, especially if it has to withstand stroms without damaging the building etc.
It is simpler to just put the house there quickly.
Couldn't you just build a tent-like scaffolding for this purpose? Maybe one that can be extended as the internal build progresses?