Or (uhn, errr, AMONGST the many ideas...)

Build a time machine in a clear space in your back yard. Get into the time machine along with the sofa. Set the time for a year right before your home was built.

Drag the time machine and the sofa to the location where your bedroom will be once they build it. Get back in and set the time back to "today". Take the sofa out of the time machine, which is now in your finished bedroom, and put it where you want it.

To get the time machine out of the way, set it to a future date and hit the button and jump out. Just remember what day you set it to so you don't end up squashed under it the day it reappears.

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