If you’re trying to date your house, you may be able to find a clue in its plastering job. Although it’s difficult to determine the age of plaster itself, you can come up with an approximate date by examining the lath behind the plaster.
The earliest lath was hand-split with a hatchet, resulting in an irregular board that expanded like an accordion. Wet plaster pressed against the lath would ooze between the splits before hardening, forming a permanent “key,” or attachment.
After the use of circular saws became widespread around 1830, split lath was still used in rural areas, but elsewhere the fastest, cheap-est way of producing lath became sawing boards into thin, regular strips. This process, distinguished by the regularity of the lath and the saw marks, remained standard into the twentieth century, when drywall began replacing plaster as the wall covering of choice.

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