·4 min
Most pre-1950 Chicago bungalows have plaster walls over wood lath. Most post-1960 homes have drywall (sometimes called sheetrock or gypsum board). They look identical when painted, but they fail differently and they take very different patches.
The 30-second test: tap the wall with a coin. Plaster sounds dense and dull. Drywall sounds slightly hollow. Plaster is also noticeably colder to the touch on a winter day.
Plaster patches need a bonding agent, two coats of joint compound minimum, and careful texture matching to disappear. Drywall patches are faster but the seam needs to be perfectly feathered or it telegraphs through paint.
If you're not sure which you have, send us a photo. We'll tell you, and we'll quote either repair the same way.