24x36 is still a window, why would it not have double stud? I mean,
it's not THAT small.
And are you sure you are using the battery powered stud finder
correctly? Read the directions. With mine, you put it on the wall
_first_, then turn it on, then slide it from side to side. And it has
nothing to do with nails either -- it measures the drywall depth using,
well, something akin to sonar I imagine, like the old knock and listen
trick -- and has no problem locating the wood stud directly through
many layers of paint and whatever, nails or no nails. Only problem is
when the wall is bumpy.
Couple more thoughts.
I had one of the early Zircon stud sensors (late '80's, early 90's I
think) It had a sensitivity wheel instead of auto calibration. This
last year I got a new Zircon stud sensor, not the cheapest, not the
very best, but a pretty good one. I think the price was pretty
reasonable. It definitely works a lot better than the old one. The
technology has improved a lot.
However, even though I do have that stud sensor. The way I normally
find studs is with a really strong magnet. I have several old disc
drive magnets and they are light but very powerful. It's easy to give
yourself a blood blister if you play with them and they slam together.
They are very strong but pretty small. I basically just gently rub
them along the wall or ceiling surface, holding them lightly. When
they get over a nail, they stick there as my hand continues sweeping.
I do that on a few nails along a stud or rafter and it is obvious where
the thing is. I did it on Monday at a friend's house that has one of
those magnetic child cabinet locks and they tried it with that and it
would stick to nails too. She loved it and started doing it all over
her walls. Find a strong small magnet and try it out!