I use a magnet to locate drywall screws/nails.

I have a couple of these: CH Hanson 03040 Magnetic Stud Finder

Test the stud finder in the house and see if it makes sense.

It looks to me like stud finders are pretty cheap. You ought to be able to get a good one for under $50. It might be worth trying to figure out if the standalone building was a home-built job, a cheaply done builder job or maybe a mostly finished kit. Around here, the stand alone garages are all alike, I suspect they were all built to the same design.

I tested the stud finder a couple of places in the house, including the original garage, which might have had the same hypothetical weirdness as the detached workroom. Both 16" OC. The stud finder gave me a lot of false positives and a few false negatives, so it's not working as well as it used to, or as I remember it used to.

I'll definitely get a new one. I'm ordering from Amazon, so it will take a few days; stand by.

The house (and probably the workroom), was built in the 1960s by the initial owner, who was a tile contractor, and acted as his own general contractor. Neighborhood legend has it that the work was done by his buddies in other trades, much of it free or discounted in trade for work he did for them.

Another neighborhood legend is that he was very difficult to work with and in the end found it hard to find subs who would work for him at all. I know for sure that he was kind of weird; the fallout shelter in the new garage is solid (!) proof of that.

Both legends could be true in part. Either way it seems probable that everything was built to code, but possibly with some unusual shortcuts where an inspector wouldn't notice or didn't care.

I think my "workroom" was originally built as an office. It has a sink, and originally had its own hot water heater and natural gas wall furnace. (There's a clumsy drywall patch where the furnace was removed, and there's still a furnace at the same spot in a greenhouse on the other side of the wall.)

I'll definitely get a new one. I'm ordering from Amazon

I'd choose one of these.

https://www.amazon.com/s?k=franklin+stud+finder&crid=KJMILHFSIC1X&sprefix=franklin+stud%2Caps%2C204&ref=nb_sb_ss_ts-doa-p_1_13

Forget 'stud finders'. Just go to Harbor Freight and pick up some rare earth magnets.

Decent (not necessarily expensive) stud finders detect abrupt change in density and thickness ,magnets detect metal nails,screws and pipes.

FWIW I've used Zircon with complete satisfaction.

I got my new stud finder today (a Franklin ProSensor M90). It has not delivered instant enlightenment, though.

My old finder has five LEDs in a tight row; this one has nine, spaced 1/2" apart. The idea is that as you move it across the wall the leading LED lights, then the leading two, then the leading three; then a set of three lit LEDs progresses toward the trailing edge, indicating the left edge, center, and right edge of a stud the whole way. Also the middle LED can flash green to indicate that "This is it, the exact dead center of a stud, right here!!!"

At some spots in my house it actually more or less works that way. At other spots I get flashes of one or two or three LEDs that appear and vanish in the space of an inch, and don't necessarily reappear if I pass the sensor over the same spot again. It's definitely a noisy result.

In the workroom the finder's behavior was less clear. I'm tempted to say "random." At any rate it's difficult to describe. As I move it across the wall, sometimes all of the LEDs from the leading edge to the center flash on at once, and a few inches further on, go off again. Sometimes I get one, two, three lit LEDs at the leading edge, but as I move the finder onward, they all wink out. Sometimes the center LED flashes green, and one or two adjacent reds flash on, with no warning from the leading edge, then they all go out again. I haven't made sense of this yet.

I looked hard for studs between the corner-adjacent slol rail and the corner. For a while I thought I had found one near the ceiling, 8-1/2" from the corner. I tried lower down and got a similar reading 4-1/2" from the corner. I tried drilling a small hole at both spots and hit air both times.

I suspect that the readings I get in the house fairly reflect the finder's quality: not perfect, but usable. Something about the shed is just really weird. I may return the new finder. It's supposed to be the best you can get for less than $75 or so, but I'm not sure it's really any better than my old one.

I measured the spacing of the existing standards on a third wall that has no windows to complicate things, and they were consistently 20" apart. I guess I have to accept that the structure was built with studs 20" OC (unheard-of) or 19.2" OC (rare for rafters, apparently unheard-of for studs). It makes no sense, but the slot rails can't lie, can they? Can they?

I'm starting to suspect that there really is no stud between the corner and the rail I want to move closer to the corner, and that's why the rail was installed so far from the corner in the first place. I'm thinking I should forget about moving the rail, and use some mending plates to tie the end of each shelf to the front of a shelf on the adjacent wall.

Something isn't right and everything points to you. Don't be in a hurry as you move the finder along the wall.

Everything points to me? Would you care to explain that?

Would you care to explain why I'm getting reasonably useful results in the house, and gibberish in the workroom? Do you think that when I go into my workroom I suddenly turn into a wild man?

"Don't be in a hurry" is meaningless. I've tried moving the finder at every speed from a few inches a second down to a slow crawl, just as I've tried every other variation I could think of. So far nothing has helped.

After that rant it appears worse than first suspected. I'm reasonably certain what I said is far easier to understand (whether true or not) than instructions for finders. Wild man is taking it a bit far but I do believe things go smoother if one doesn't start seeing flashes of red at the first sign things aren't going as planed.

<response to klem1>

Of course it's easy to understand. It's just totally unsupported (so far, despite my invitation to you to justify it), and frankly, offensive. If you actually paid attention to what I said, you wouldn't have considered writing that last sentence.

</end of response to klem1>

I think the finder is telling me that the location of these studs is one of those things that Man was not meant to know. <g> I'm going to forget about finding a stud where there probably is none, and anchor the rail with toggle bolts or mollies.

I'm going to leave the two stud-anchored rails in place and add a third one attached to the drywall. I think a rail has at least five bolt holes, so I should be able to get a load capacity of at least 250 pounds. (That's for one of three supporting rails. The other two, remember, are anchored in studs.) That should be plenty. I use these shelves to hold small garden tools and chemicals. If I need to put a crate of tuna-fishing sinkers or some lead plutonium fuel rod canisters on them, I'll just have to remember to put 'em between the studs!

Hi,

Frustration makes the job harder. Use a small finish nail to find the studs, then go from there.

Good Luck Woodbutcher

Could the workroom have been built using metal studs, and your stud finder can only correctly detect wood studs? If find this one is the most user friendly and very accurate.

I am not endorsing the product, just sharing my observations over the years using different models of stud finders.

woodbutcher_ca, the only way to eliminate frustration from a job completely and permanently is to finish it.

wOlley32, I took off a wall plate and checked a stud. It's wood.

I found that the two original rails are approximately 19" apart, and another 19" takes me right to the corner. Unlikely as it seems, the structure was built with studs 19.2" OC, and there is no additional stud between the proximate rail and the corner -- the next stud is in the corner, where it's useless for mounting another rail.

I fixed the third rail to the wall with six drywall anchors, total load capacity 510 pounds. One shelf is up and in use now. For the others I just need to get some more slot brackets.