can i fusion 2 buildings in 1 building ?

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when using DesignBuilder i made a mistake by building two buildings instead of two blocs , i have one building contain 2 floors R1 and R2 but the mistake was that i build R1 as a building not floor (bloc) and R2 as well as a building in the top of it , is there any method to fusion those 2 builldings in 1 building whith 2 blocs ??