Delray's older core — the frame vernacular and bungalow-era houses around Swinton Avenue and the blocks east and west of it — dates mostly to the 1920s through 1940s, with pockets like Del-Ida Park and Nassau Park built out in that same window. Away from downtown, the city fills in with postwar and later single-family construction and a good amount of condo and townhome product along the coast and in the western annexation areas developed from the 1970s onward. It's a mixed housing stock by age in a way that a lot of Palm Beach County suburbs aren't.
On the older homes, that means original wood-frame roof decks and, in some cases, metal roofing that's been re-done more than once as styles and rules changed; on everything built since the 1970s it's the standard South Florida mix of concrete or clay tile and asphalt shingle, with the usual tile-slippage and shingle-wear failure modes. Flat and low-slope sections show up more often downtown, over additions and mixed-use buildings, and need modified bitumen or single-ply attention rather than a shingle repair.
Delray Beach's real wrinkle is its five locally designated historic districts — Old School Square, West Settlers, Del-Ida Park, Nassau Park and Marina — where any visible exterior work, roofing included, goes through the Historic Preservation Board for a Certificate of Appropriateness before the city issues a building permit. The board has approved standing-seam metal roofs on historic Swinton Avenue properties in past sessions, so metal isn't off the table, but the material, color and profile all get reviewed, and that review adds real time to the schedule on top of the standard permit process. Outside those five districts, it's a normal Florida Building Code permit with no extra board.