Can I build a duplex in Birmingham?

No, not in the single-family districts. Two-family dwellings are allowed only in the R4 Two-Family Residential district (§ 1.10). In R1A, R1, R2, and R3 the use lists do not include two-family dwellings, and an unlisted use is not permitted (§ 1.13).

If your lot is zoned R4, the basic standards are:

• 3,000 sq ft of lot area per dwelling unit
• 25 ft front setback and 30 ft rear setback
• Total floor area capped at 40 percent of the lot
• Height limit of 35 ft and 2.5 stories (§§ 2.12-2.20)

On a single-family lot, adding a second unit would point toward a rezoning rather than a variance. Check your district on the city's zoning map, then confirm the path with the Planning Division at 248-530-1850.