Just moved in to an old victorian home and the wife wants shelves in the mud room. Now I know what you are thinking "Shelves?! Seriously?!", Just hear me out.
These are 6 foot shelves with 4 steel gussets each. It's laundry room shelves so they will most likely hold liquids. I figure, 10-20 lbs per linear foot.
I started out be knocking and looking for studs. No luck, not that I'm very good at it anyway. I found a sheetrock seem above the doorway about 8 feet away. I measured over 16" and drilled to see what was underneath. Just sheetrock. Lots of it. I drilled a couple of test holes in the sheet rock beneath the height of the washer/dryer (the shelves will be above them). I only hit sheetrock. Once again, a lot of it.
Next I noticed that there was a 1/4 gap between the floor and the poorly installed trim. After looking at what I'm up against, it appears to be a rotted and crumbling plaster and lath wall, with a sheet of something that appears to be a thin layer of MDF and covered by plaster, covered by 1/2" sheetrock.
My first long shot of a hope what that I could sink a 3" decking screw deep enough to hit the MDF-ish stuff. If I hit it, it still wasn't holding.
Next I tried 3/8" toggle bolts. The longest screw I could find was not long enough to allow the wings to clear the wall.
Finally I gave in and tried 150lb plastic anchors but I couldn't get them to hold. Honestly I wasn't surprised.
I've had problems like this before in older houses and I considered hanging a piece of 3/4" waferboard first, but with all the trouble I had getting anything to hold I'm actually worried about the wall supporting it.