Stud/joist finder that works?

rogerv_gwOctober 14, 2007

I'm trying to stop some squeaks in my bathroom floor. It is vinyl, and there is no access from below. I'd like to use those special screws that break off, and then just a dab of matching caulk to seal the holes.

My problem is finding the floor joists through the floor before drilling holes. To do that, I'm looking for a stud finder type thing that works. I have 2 different Zircon stud finders, neither of which gives stable, repeatable results. I can kind of hear the transition between hollow and solid by knocking on the floor, but I'm not sure enough to start drilling.

Can anyone recommend a stud finder that really works? I realize that it depends on construction and all that, but there must be one of these out there that really works.

It also seems to me that the subfloor (probably particle board) must be nailed into the joists. Is there any reliable way to find those nails with drilling holes?



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Oops, I didn't mean "with drilling holes" at the end, I meant "without drilling holes".

    Bookmark   October 14, 2007 at 8:37PM
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I was very frustrated with Zircon (the basic model that you get for 25 bucks from HomeDepot) in the beginning, but once I've learned to used it, it gives me 100% accuracy. Take pen and make small marks where the stud finder detects the stud. The points will eventuall start to converge between multiple readings.

However, I do have a problem with your suggested approach, it just begs for water problems in your floor. You need to remove the vinyl, use wood screws to tighten the particle board, then drive down any nails that stand tall, then replace the vinyl.

    Bookmark   October 15, 2007 at 11:42PM
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Thanks for the advice. I played with the Zircon for quite a while, and the results were pretty random. Every time I tried it I got different results, never the same twice.


    Bookmark   October 16, 2007 at 1:08AM
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The best way to tighten up the floor is to remove the vinyl & any overlayment such as masonite down to the subfloor. The reason for taking off the overlayment is that it is often just stapled to the subfloor, not through to the joists.
The subfloor, probably plywood, will be nailed to the joists below. Use standard drywall type screws about 1" to 1 1/2" long to re-attach to the joists.
Put on an underlayment & refloor with vinyl if that is what you want. It's possible the underlayment is squeaking against the subfloor.
Not the answer you wanted, but what I think is the right way to do it.

    Bookmark   October 16, 2007 at 1:11PM
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If it were me, I'd use the old fashioned $3 stud finder which has a little magnet that you can observe: when it passes over something metallic, it swings visibly. Since the fasteners holding down the subflooring are nailed into the joists, locating the old fasteners should show you where to put the new ones. Further, once you locate one of the joists, the others should be parallel to it, at regular intervals (often 16"), and you can pretty quickly mark the locations with masking tape, a yardstick and a pencil. Use screws and drive the heads just below the surface, fill them in with floor leveling compound, and put new vinyl down.

Unless you have had the old flooring tested to ensure it doesn't contain asbestos, don't tear it out. You can put down a new layer on top of it unless the old one isn't well-adhered. If the old flooring material is not well-adhered, and it tests positive for asbestos, then follow the repair procedure described above, lay down another 1/2" of underlayment which you can screw and glue down over the old flooring, and then put down new vinyl.

    Bookmark   October 16, 2007 at 3:19PM
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I can still do as well as the finders just tapping with my knuckle.
All the finders fail on plaster walls. The metal mesh used to strengthen gives them fits, as will as the overall thickness (usually about 3/4 inch, but sometimes thicker).

    Bookmark   October 16, 2007 at 6:27PM
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I didn't know stud finders worked on solid plywood. I'll have to test that. (I have the Zircon yellow one, which is very good. My previous basic old Zircon grey one begain giving random results.)

Anyway, you could use the stud finder on the ceiling below to get a general idea of where they are.

Or how about peeling up a corner of the flooring to see what's going on underneath to locate one joist. You might have to also peel up a bit of underlayment to see the nail pattern on the subfloor.

I'm hesitant to say this, but how about making an access from below to find a joist? To mark it, drill a tiny hole upward adjacent to one of them. Patch and paint afterward.

    Bookmark   October 17, 2007 at 7:24AM
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Some good thoughts here, thanks very much. I don't think that the flooring is asbestos, unless there is another layer under the top layer. I believe that the layer on top is about 1991 vintage from the previous owner's remodeling.


    Bookmark   October 17, 2007 at 6:59PM
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All good comments, but has anyone had experience finding the joists under a hardwood floor? There is no access from below. Now I possibly could use the the Zircon on the finished ceiling below, but accuracy is still an issue. I certainly don't want a bunch of "test holes" in my hardwood floors that would have to be patched. Thanks, Jim

    Bookmark   February 14, 2011 at 6:50AM
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Sophistic: I would think your best best is from below. Cut one hole into the ceiling and locate a joist. Us ethe know location to calibrate your Zircon and locate the other joists which should be at a fixed spacing.

    Bookmark   February 14, 2011 at 9:26AM
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If the hardwood is installed, why do you need to find the joist anyway?

    Bookmark   February 14, 2011 at 12:08PM
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If your house is built well and you know which way the joist run alot of times they will line up with the wall studs, but this is not always the case. And if your hardwood was installed professionally it should run perpendicular to the floor joists (once again not always the case) and you maybe be able to find nails around the edges, but can't be sure of these.. I've never seen a studfinder work well on anything thicker or denser than 5/8 drywall but their could be one out there. Most the ones I've used will go off on spots of thick sheetrock mud. Why are you looking for joist through hardwood though, normally it and the subfloor is plenty to attach to.

    Bookmark   February 14, 2011 at 10:56PM
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"Why are you looking for joist through hardwood though, normally it and the subfloor is plenty to attach to."

Not if the subfloor is the source of the squeaks.

    Bookmark   February 15, 2011 at 9:41AM
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