Lath-and-plaster walls are common in older houses (those constructed from the late 18th Century until the early 1950’s, when drywall became the common building technique.) Whether it’s an oil portrait of an early ancestor or wall-hung kitchen cabinets, securing things onto older lath-and-plaster walls can present a bit of a dilemma.
First, let’s talk about how lath-and-plaster walls were constructed. Once the house was framed (generally with studs spaced 16” on-center), the exterior sheathing and siding completed, and the doors, windows and mechanicals (plumbing, heating, electrical) installed, the plasterers would start covering the walls with wood strips called “lath.” The pieces of lath were generally 3/8” thick, about 1-1/2” wide and 48” long, with a gap of 3/8” between them. A thick layer of gypsum-based coarse plaster (gray or brown colored) was troweled onto the lath until it oozed through, forming “keys” that held the plaster to the lath. A thin layer of white finish plaster was applied after the coarse layer had cured.
To attach lightweight items to this type of wall, it’s usually enough to drive a nail or screw into the plaster surface and catch a piece of the lath beneath it. If the nail goes through easily, it didn’t get into the lath; pull the nail out and try again, 1/2” higher or lower. But, if you are hanging anything on a plaster wall that weighs more than a couple of pounds, the hard and fast rule is to find a stud, and screw or nail your item to that. Switch and outlet workboxes should also be attached directly to studs, so they won’t become loose and move about as you use them. (Read the rest)