Mixed-use property: two uses, one parcel, frequent errors
A shop below and a flat above are assessed differently, and the split is often stale.
A building with commercial space at street level and residential above is common on Illinois main streets and is assessed as a blend.
Where it goes wrong
- The split is stale. An apartment converted to office years ago, or the reverse, and never re-coded.
- Square footage allocated wrongly between uses.
- Wholly commercial classification for a building that is mostly residential — which matters most in Cook, where classes are assessed at different levels.
- A vacant upper floor assessed as though let.
What to bring
A floor plan with areas by use. Leases showing what is actually let and for what. Photographs of vacant or unusable space. If an upper floor is unusable — no separate access, failing a code requirement — document it; that is a value fact, not an excuse.
Comparables are hard
True mixed-use comparables are scarce, which makes the income approach and factual corrections more productive than a uniformity argument. Where you can find genuinely similar buildings nearby, use them, but expect the assessor to distinguish them.
This is general information about how Illinois assessments and appeals work. It is not
legal advice, not an appraisal, and not a prediction about your case. Deadlines and rules differ by
county — check yours with your Board of Review.