Tumbledown is a related term of unsubstantial.
As adjectives the difference between tumbledown and unsubstantial
is that tumbledown is in disrepair; poorly maintained while unsubstantial is (archaic).
tumbledown
English
Adjective
(
en adjective)
in disrepair; poorly maintained
:They lived in a tumbledown shack on the edge of the woods.
Synonyms
* bedraggled
* broken-down
* dilapidated
* ramshackle
* ruinous
* rundown
* tatterdemalion