At what size does an upstairs make sense?

[JohnMo]

52 minutes ago, Crofter said:

For context, the first house I built was 43m² internal, and the possible next one would be similar but with a second bedroom. I'm not sure if splitting such a small house over two floors works...

Go around new housing estates, many houses are that size and smaller 

[G and J]

1 hour ago, Crofter said:

For context, the first house I built was 43m² internal, and the possible next one would be similar but with a second bedroom. I'm not sure if splitting such a small house over two floors works...

It’s a bit like the loft conversion debate really.  Loss of floor area to stairs vs usable floor area gained and all that.   Thankfully usually there’s more important overriding factors that determine the plan…