Nice work on the visualization. For the reference to certain residences being two stories you can look to a SBS comment on Update #25 from May 26th (both SBS comments from that day are included below for ease of reference...)
Creator Soulbound Studios on May 26
And I can confirm what others are saying. The cottage is 8m x 8m, whereas the parcel of land is 64m x 64m. Plenty of space for everything. Incidentally, the Manor is 24m x 14m, x2 floors. The Townhouse is 12m x 8m, x2 floors.
Creator Soulbound Studios on May 26
Hey Justin, the Townhouse, Villa, and Manor already include a second floor. As for Tunneling, I don't have the values for that off-hand. I might be able to get it from the dev team tomorrow.