What makes a work Gothic?

Wuthering Heights contains undeniably Gothic elements:

In true Gothic fashion, boundaries are trespassed, specifically love crossing the boundary between life and death and Heathcliff's transgressing social class and family ties. Brontë follows Walpole and Radcliffe in portraying the tyrannies of the father and the cruelties of the patriarchal family and in reconstituting the family on non-patriarchal lines, even though no counterbalancing matriarch or matriarchal family is presented. Brontë has incorporated the Gothic trappings of imprisonment and escape, flight, the persecuted heroine, the heroine wooed by a dangerous and a good suitor, ghosts, necrophilia, a mysterious foundling, and revenge. The weather-buffeted Wuthering Heights is the traditional castle, and Catherine resembles Ann Radcliffe's heroines in her appreciation of nature. Like the conventional Gothic hero-villain, Heathcliff is a mysterious figure who destroys the beautiful woman he pursues and who usurps inheritances, and with typical Gothic excess he batters his head against a tree. There is the hint of necrophilia in Heathcliff's viewings of Catherine's corpse and his plans to be buried next to her and a hint of incest in their being raised as brother and sister or, as a few critics have suggested, in Heathcliff's being Catherine's illegitimate half-brother.

What makes a work Gothic is a combination of at least some of these elements: read:

edu/english/melani/novel_19c/wuthering/gothic.html