“The tunnels branched out some 200 feet and two-stories beneath the basement of the house.”
There is a terrible shortage of hyphens in the world, so please don’t use one unnecessarily.
Adjectives are flimsy; nouns are stout. A two-story house needs a hyphen, to hold the pieces of the adjective together. Two stories don’t need a hyphen, because stories is a big strong noun.
If you find a spare hyphen lying around, by all means, save it for your next two-word adjective.
English Is A Complicated Language 