A 2-flat looks like one building and behaves like two. Two kitchens, two sets of baths, often two of each mechanical system, plus shared elements like the roof, masonry, porches, and common stairs. Rehab budgets on 2-flats go wrong when the scope treats the building as one big house.
How we scope a 2-flat
- Unit by unit. Each unit gets its own scope and finish level, whether you're renting both, living in one, or selling the building.
- Separate systems, planned together. Heating, water heaters, electrical service, and meters are assessed per unit, and we plan the work so it's sequenced sensibly across both.
- The shared shell. Roof, masonry, windows, and common stairs affect both units and the appraisal. We flag them early because they're the items that blow budgets.
- Porches. Rear porches are a signature of Chicago multi-unit buildings, and they're a safety and code item. We assess them as part of every 2-flat scope.
- The basement. Whether it stays storage, gets finished, or becomes a unit changes the scope, the permits, and the value. Decide before you buy.
Porches: what Chicago requires
Chicago holds existing porches to its minimum requirements for existing buildings regardless of when they were built, and deficiencies must be corrected as part of any permitted porch repair. A few rules that shape a 2-flat budget:
- A building permit is always required to repair or replace structural porch elements, and porches must be able to support 100 pounds per square foot.
- On a multi-story porch, repairs up to 25% can go through the city's Express Permit Program without design drawings. Repairs over 25%, or a full rebuild, need drawings from an Illinois-licensed architect or structural engineer.
- A full rebuild is held to new-construction standards, with limited exceptions under the Chicago Building Rehabilitation Code.
Basement units
Chicago expanded its additional dwelling unit ordinance in September 2025, which allows a conversion unit in a basement or attic of an older 1–4 unit building in eligible areas. Whether your basement qualifies depends on zoning, the building, and code requirements for the unit itself. We'll tell you what it would take before you plan around it.
For every exit strategy
- Flip: both units finished to what buyers in that neighborhood expect.
- BRRRR / rental: durable finishes, units finished in rentable order, and lender documentation if you need it.
- Owner-occupant investor: the rental unit done first so it's producing income while you finish yours.
Before you buy the building
A 2-flat's price can hide a five-figure porch, a boiler at end of life, or a basement that can't legally become a unit. Send Mason the address before you make your offer, and use Mason's 3-flat checklist. Most of it applies to 2-flats too.
Pay as the work gets done
Your full price is quoted up front, then paid through weekly labor draws credited toward the project total, sized to the project's contract, scope, schedule and labor requirements, with a $4,000 weekly minimum. See pricing.