We will not give you a decade, because the date a two-flat was built belongs to each building, not to the building type. To find yours, check the Department of Buildings records for the address and your title and tax documents. The age is worth knowing because it points to what the building probably needs: older masonry and mortar, steel lintels, original porches, and lead paint rules for homes built before 1978.
Chicago two-flat history is a topic where a lot of confident dates float around, and we are not going to add to them. We cannot source a single start date or era for the building type, so we will not invent one. What we can tell you is how to find the age of your own two-flat and what that age means for repairs.
For the basics of the building, see what a Chicago two-flat is and what it needs from you. For all building types, see our Chicago building types guide.
How do you find out when your two-flat was built?
Start with your building, not with the type. The age of one two-flat says nothing certain about the one next door.
- Ask the Department of Buildings what permit and record history exists for your address. Records for older buildings can be incomplete, so a missing record is not proof of anything.
- Check your closing documents, title records and tax records. A year built listed in one of them is a starting point. Treat it as an estimate until something else backs it up.
- Compare against what you can see. Original details such as the brick, the window openings, the stairs and the porch framing can tell a mason or an architect roughly how old a building is, and whether it has been altered.
- Ask your attorney or title company if the date matters for a sale, a refinance or an insurance claim.
If the building is landmarked or sits in a landmark district, the City has its own records. Landmark properties may not get the City's no-permit exemptions (City of Chicago), so ask the Department of Buildings and the Department of Planning and Development before you plan exterior work.
What does the age of a two-flat tell you?
Age does not tell you condition. Two buildings from the same decade can be in very different shape depending on who maintained them. What age does tell you is where to look.
Older masonry and the mortar in it. In an older wall, the mortar was built to be the softer part of the wall. The National Park Service says repointing mortar must be softer and more vapor permeable than the masonry units and no harder than the historic mortar, and calls the assumption that harder is better a common error (NPS Preservation Brief 2). That is preservation guidance, not a City mandate, but it is the reason a hard modern patch on an old wall is a problem. We cover it in what a failing brick two-flat looks like.
Steel over the openings. Steel lintels over windows and doors need periodic maintenance in a harsh climate to avoid corrosion (Brick Industry Association). An older building has had more years for that to go wrong.
Original porches and stairs. The City's rule is the same no matter the age. Exterior stairs, porches and balconies, including guards and handrails, must be structurally sound and properly anchored (City of Chicago). A porch that has outlived several owners may have had repairs that nobody documented.
Paint and lead. The EPA's renovation rule applies to paid work that disturbs painted surfaces in homes built before 1978, and requires lead-safe certified firms and trained renovators (EPA). If your two-flat could be that old, ask your contractor how they handle it. We follow the rule.
On older brick two-flats the same few things keep coming up: tired mortar, a lintel that has been rusting out of sight, a back porch that has been patched more than once, and a roofline that has never been fully redone. The age of the building explains why they pile up. It does not excuse them to an inspector. This is a typical pattern, not a particular building.
Do you need to know the exact year?
For most repairs, no. You need to know what is in the wall, what shape it is in and what the City requires. The exact year matters more for a few situations: a landmark or historic review, a lead-safe work question, an insurance or sale document, or a contractor who needs to match old materials.
A permit is the main thing to confirm either way. Chicago requires a permit before most construction, repair and demolition work begins, with a limited range of exemptions (City of Chicago). Check with the Department of Buildings before you assume a repair is exempt.
If you are not sure how old your building is or what it needs, Akats can walk the outside with you. We are licensed and insured in Illinois and handle masonry, tuckpointing, porches and roofing in-house. See our services and ask for a free estimate. If you are buying, see what to check outside a two-flat first.
Common questions
There is no single date we can give you. Two-flats were not built all at once, and the age belongs to each building. To find yours, ask the Department of Buildings what records exist for the address and check your title and tax documents.
No. Age does not equal condition. A well maintained older building can be in better shape than a neglected newer one. Age tells you where to look first: mortar, lintels, porches and, for homes built before 1978, lead paint rules.
Start with the Department of Buildings records for your address, then your closing documents, title records and tax records. Older records can be incomplete, so treat any single year as an estimate. A mason or architect can also read the building itself for clues.
Sources
- City of Chicago: Guide to Building Permits: What Types of Work Do Not Require a Building Permit?
- U.S. Environmental Protection Agency: Lead Renovation, Repair and Painting Program
- National Park Service: Preservation Brief 2: Repointing Mortar Joints in Historic Masonry Buildings (PDF)
- Brick Industry Association: Technical Note 31B: Structural Steel Lintels (PDF)
- City of Chicago: Code Modernization Ordinance, including Title 14X Minimum Requirements for Existing Buildings (PDF)
Facts last checked: October 7, 2026.
This article explains general rules and common situations in Chicago. It is not legal advice, and City rules change. For a specific property, check with the Chicago Department of Buildings or a licensed professional.