How to mount a plasma TV on a plaster wall

kltaylorJune 24, 2005

I have a 95 LB 42" plasma TV that I want to mount using an articulating swivel

that pulls out 30" from the wall. The installation notes for the mount say to attach it to a wood or concrete stud. I assume my plaster walls don't have studs. (This is a 1929 apartment in NYC.) What to do? I need the "arm with an elbow" mount because I'll be viewing the TV from armchairs and couches that are to it. Thanks.

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Plaster walls are mounted on lath, which is in turn nailed or screwed to studs. There will be studs behind the lath, on 16" or so centers. You'll screw through the plaster and the lath to reach the studs (about 3/4" inch to an inch behind the surface of the plaster). This is important, because the plaster itself won't hold such the TV, and if you just screw it into the lath, you'll likely pull out a large section of plaster.

You can locate a "stud finder" at the hardware store that theoretically locates the screws or nails holding the lath to the studs, but often they're not very effective. You can also "sound" the walls by pounding lightly with a cloth covered hammer to try to tell where the studs are (the sound will be less hollow), but actually pinpointing the stud is going to be a bit tricky. If you screw in the mount attaching screws and they pass through the plaster and lath and there is no longer resistance, you're hanging in thin air. They should be very rigidly mounted into the studs for such a large television.

    Bookmark   June 24, 2005 at 10:19PM
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Aha. Thanks.

    Bookmark   June 25, 2005 at 2:13AM
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Stud finders won't find studs in a lath and plaster wall.

If the carpenters who installed the baseboards knew where the studs were, they may have nailed the baseboards into them. If you can't see the nails, you may be able to find them using a magnet, or a metal detector. Then you can follow a line up. But do a test hole by drilling before you commit to hanging a heavy TV.

    Bookmark   June 25, 2005 at 7:17AM
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Depending on the building construction you may not have studs. Plaster can be placed directly on a masonry wall.
If the wall is an interior wall it is likely a stud wall with plaster. The baseboard nail locations are not a good indicator of studs in most plaster work.
To create a level wall plaster Âgrounds are used around all openings and edges were plaster ends. These are typically 1 inch thick wood strips. At the baseboard they are often 2-3 inches wide (at windows 1-2 inches is common).
The baseboard is attached to the plaster grounds and not directly to the studs.
If the walls are smooth plaster repairs are pretty easy, so you can use a small (1/8 inch) masonry bit to go looking for the studs. The studs are typically on 16 inch centers in older work. Measure from the nearest corner and drill a test hole. For a heavy load you need to have the exact center of the stud, so count on drilling a few holes.
If the mounting bracket is large enough, it will cover at least some of the errant holes.
To mount into the studs you need to remember the plaster is at least ¾ of an inch thick and get screws with enough length to get well into the stud.
If you are on a common wall it may be masonry and mounting gets a lot more complicated. A unit that hangs away from the wall produces a large tension (withdrawal load) on the fasteners and many masonry fasteners do not have good tension load characteristics. Drop in expanding steel anchors have good tension, but are larger and more difficult to install correctly. The strength is also very dependent on the exact material the anchor is driven into.

    Bookmark   June 25, 2005 at 10:58AM
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or just drill a few small holes to find where the studs are, then use a bit of plaster or polybond to fix the holes & paint, if the studfinder does not work

    Bookmark   June 29, 2005 at 2:58PM
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Studfinders still work on plaster + lath walls, you just need to get a slightly better than average one. Make sure you just move horizontally, the way studfinders work is that they detect differences in the reflectivity of the wall insides. If you move up and down you will sometimes get false readings from the gap between the laths. Make sure to double check by looking for the stud a few feet above where you first find it and you will do fine. You should still test the spots first, but I would do it with a thin finish nail.

    Bookmark   June 30, 2005 at 3:44PM
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Having installed dozen of them to be modest , you need a very good stud finder the cheap one will not work , if it is going to be your only use for it get it from these large mega home center keep the packaging clean and return it clean, I let you give them the reason .... They are all made to be hang on STUD , and must be able to support 3 x the weight they are intended to be used on . if they fail they will kill you plain and simple .lot of good thread on previous posting .

    Bookmark   July 1, 2005 at 1:00PM
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