We have built the typical free-standing 4-level garage shelves(similar to this) & want to secure it to the house frame in the garage.
The whole thing is pretty sturdy but we just want to be safe & this is in California, where there is a threat of earthquakes.
What kind of screws do you recommend & how long should they be? Maybe 1-2 screws per shelf to the frame?
Here is a photo & rough estimate of the measurements:
I'd go two screws per wall stud thru the top and middle shelf. The weight of the thing is supported by the structure itself so all you need to do is keep it from falling over. Use a 4 1/2 inch timber tech or a 5/16 lag with a washer and you'll have two inches of screw into the stud which is adequate but a minimum. Make sure you install shims or a spacer to fill that gap before you run your screws.
I would say that you'll be okay with a 4" screws and a shims through the top shelf. 3 sets one on each end and a set in the middle should prevent your shelf from falling over. The top is where you'll get the most pulling force so if you screw the shelf up there you'll end up stopping it before it gains any gravitational force as it falls. Lag bolts will certainly do the trick but are pretty hefty. Also keep in mind that how you load this shelf will affect it's stability. Put your heavier items toward the bottom. You don't need very much to typically hold the shelf in place. The challenge is brought about by earthquakes. So you'll have to assess the likelihood of being hit by one and adjust the strength of your fastener accordingly.
Another thought entirely is to notch the bottom so that the rest of the shelf will sit flush on the wall. You won't be taking too much out of the back legs (1/2" more or less) and so the vertical strength of the shelf will not be compromised.
