Plywood behind drywall - stud finder doesn't work

[Relax]

My garage is finished, and there appears to be a layer of plywood between the drywall and the studs. I've tried a couple of different stud finders and they both can't detect the stud through the plywood (including one that is supposed to have a deeper scanning range). They both work on the backside of the wall (inside the house), but that still took some trial and error to find the stud centres, and this won't work for the other walls or the ceiling. Can anyone recommend a good stud finder that will work under these conditions?

 

[zeeway]

The plywood is likely nailed to the studs on the usual 16 inch spacing. Use a super magnet to find the nailheads in the plywood. I would guess the sheetrock would also still be nailed on the 16 inch centers as well.

 

[Viper98912]

I had this issue as well, and had to use the inside of the house to find the studs, along with some additional measuring and additional hole patches I needed to do in the wall when I was done

 

[The Cobbler]

locate an electrical box, there will most likely be a stud on one side or the other. I usually figure the box is on the right side of the stud because most people are right handed and therefore it's easier to nail a box on the right side. (not always the case but a good start point )
once you have located the stud measure 16" or 24" O/C

 

[rburke65]

Yes the electrical boxes are a definite help as stated above. Pull the covers off and you should b able to determine the stud location and go from here here.

 

[JMURiz]

I've had luck with a studfinder that has as deep-wood setting.

My old Rayobi has it...it works going through Hardiboard and OSB to find the studs behind.

 

[Reese]

Hanson makes a stud finder that uses two rare earth magnets that should be available at a big box for around $10. I use it for locating studs in my house with lathe and plaster walls, works like a champ.

 

[gungatim]

why do you need to find the studs? can you get away with just screwing into the plywood, or using wing anchors maybe? otherwise in addition to what has already been posted, the old drill a bunch of small holes horizontally till you hit something always works...then patch the drywall