Will it work on plaster walls

Hello Linda. Because of the varying density of materials that make up lath and plaster constructed walls, a standard stud sensor tool will not work to find the studs. ( It is stated on the packaging “Not recommended for use on lath and plaster”). The preferred technique would be to use a Zircon Studsensor that includes a “metal scan” mode, like the L350. This will allow you to search out and map the nails that hold the horizontal lath pieces to the studs. This way it’s possible to map out the studs accurately. For more information on this please contact our tech support through the Zircon website. Thank you.