Can magnets find wall studs?

Q: I read your column about anchoring heavy objects on walls, and I wanted to pass along a stud-finding technique that I’ve started using to great advantage. I use powerful rare-earth magnets (which I buy from Lee Valley Tools) to locate the fastener heads in walls. Even with a little 1/4 -inch diameter rare earth magnet, I can sense old nail heads through my inch-thick plaster walls. (I just ordered some 3/4 -inch diameter magnets to make this easier yet.)

Once I find the first nail or screw head, I mark the location with a piece of blue masking tape and find and mark others in the same stud above and below my first mark. Then I repeat this process from side to side until I’ve mapped out the area I need to work in. This technique is also useful when trying to decide where to cut into drywall for new outlets or switches.

P.S. I also wanted to point out that all studs are 1 1/2 -inch thick, regardless of their width (2 by 4, 2 by 6, 2 by 8, etc.) and whether they are steel or wood. — Tim G., Akron, Ohio

A: That’s a technique I hadn’t thought of before — especially since I’ve been spoiled rotten by electronic stud finders these past few years.

I was sitting here lamenting the fact that I didn’t have any rare-earth magnets to test this method out, when my significant other poked his head into the doorway and said, “But we do! Remember that guy who was selling those cool ‘singing magnets’ at the swap meet last summer? Well, I bought a set!” And he dashed across the hall to his office to get them.

So, we just spent the past half-hour merrily running a couple of small, powerful ovoid magnets across the walls, marking where we thought the studs were indicated with a pencil. I cross-checked them afterward with the electronic stud finder. The results? So-so. Of course, a couple of mini-magnets designed for entertainment probably aren’t the best products to test with.

The closer the studs were to the outside of the wall — in our fixer-upper, some are behind an inch of plaster, others are behind a quarter-inch of modern drywall — the better the read we got. The magnets located roughly half of the studs tested, while the electronic stud finder located all but three.

Many thanks for the tip, Tim! Rare-earth magnets are sold through specialty hardware retailers, but may be available at the local hardware store, too.

HOME TIP: How long will your new coat of paint last? Interior paints keep their luster for about five years; exterior paints for about eight.