The D.C. Council on Tuesday tentatively adopted major rent control legislation, taking a first step, members say, toward protecting the District’s dwindling affordable housing stock.

The bill, which must be voted on a second time before final approval, caps annual rent increases at 2 percent plus the cost of living, or just cost of living for the elderly and disabled. It eliminates rent ceilings — the maximum amount a landlord can charge on a single unit — and limits hikes on vacant units to 30 percent.