dilapidated

(verb) bring into a condition of decay or partial ruin by neglect or misuse. Synonyms: dilapidate.

(verb) fall into decay or ruin. Synonyms: decay, crumble, dilapidate. Example: "The unoccupied house started to decay."

(adj) in deplorable condition. Synonyms: bedraggled, broken-down, derelict, ramshackle, tatterdemalion, tumble-down. Examples: "A street of bedraggled tenements." "A broken-down fence." "A ramshackle old pier." "A tumble-down shack."