Framing and Sub-Flooring - lag bolts into i-joists for hanging storage

I want to hang some shelves from my garage ceiling (drywall over engineered i-joists, living space above garage). The shelving attaches with 5/16" lag screws. Are there any guidelines for what you can/can't screw into i-joists (size, number, weight supported)? This is just for normal household storage, nothing out of the ordinary in terms of weight.

Chances are it will probably be ok but does the manufacturer of the shelves have a weight limit on their product? In other words, I'm trying to get a number to connect to normal.

IIRC..most I joists only have a 1 x 2 or so as the upper and lower members? Boy I'd be concerned about getting them dead center. I never hung anything more than a little swag lamp or decorative thing from mine.

I will take a look at my i-joists later (the garage ceiling is finished but there is another area of the house where they are exposed), but I think the top/bottom pieces are more than a 1x2.

The shelving I'm looking at is from Quick-Shelf. It uses U-shaped wire hangers suspended from two 5/6" eye screws to hold shelving material of your choosing. I will run the shelving perpendicular to the joists, so each joist will have two eye screws in it. Each hanger is supposed to support up to 600 lbs so that's 300 lbs. per screw, 2 screws per joist.

I don't plan on putting nearly that much weight on it, though -- for an 8'x2' shelf with 4 hangers that would work out to 150 lbs. per square foot. so my main concern is making sure that putting 5/16" holes in the bottom of the i-joists isn't going to weaken them. However, if you can give me an idea of how much weight would be reasonable to hang from the ceiling that would be good to know too.

picture of shelves (http://www.quickshelf.com/photo_folder/overhead-garage-shelving.htm)

Engineered I-joists are meant to support a load from above, not from below. This is a glued together product of three pieces, top, bottom chords and center web. You would be trying to pull it apart from the bottom up. In all literature I've read, the largest nail into/through the bottom chord to a bearing material is 16d, about 1/8" thick. 1-1/2 times that- pulling from the bottom, not the top, couldn't be good. Is there any way to attach to the plywood above? You are messing with the tension half of the product (under the most strain), I would be careful not to weaken an already slim product, for fear of failure and having the load above become the load below.
Be safe, G
Be safe, G

I agree with the above posters about the ills caused by drilling directly into the I joists. However, It may be possible to "spread the wealth" so to speak, by attaching 2x6's across at least 3 joists using 3" decking screws, then applying your lags. That should help spread the weight out a little and give a medium for aligning your shelves where you want them. 150 lbs per sf is heavy.....more than your refrigerator, so that much weight hanging from the joists may cause problems, not only for the joists, but lags won't hold that much weight in a vertical fashion.

If I go the 2x6 + deck screws route, two questions:
1. how much weight can each deck screw support (i.e. how many deck screws per 5/16" lag)?
2. how much weight can I hang from a lag in the 2x6 half way between joists before the 2x6 starts to bend?

I agree with everyone that caution is called for (which is why I asked the question in the first place). However, two things to note:

150 lbs/sq. ft. is the weight the shelf hangers claim to support, but as I said I will not put nearly that much weight on the shelf. I'm just going to be storing usual household stuff -- Christmas decorations, etc. No lead bricks, engine blocks, etc.

I'm skeptical that nothing bigger than a 1/8" nail can go into the bottom of an i-joist. Lots of houses have i-joists in the garage ceiling, and I bet most/all of them have garage door openers hung with fasteners a lot bigger than that. Not a lot of weight, granted, but still there is a hole in the joist chord.

Weyerhaeuser's toll-free tech. info # 1-800-648-3936 # 5 - deseign
Need the size - 9-1/2" or #110 eg.------ span in feet--------load on it now, pounds.
Said a 5/16" may be OK, if drill pilot hole first AND the load is not at 80% of maximum now. If another brand, just call after finding number on web.
Be safe, G

That's a great idea to call the manufacturer. Unfortunately I haven't been able to find a working phone number. The joists are Jager Engineered Wood Products JSI 3000,
about 12" high (I think the nominal size may be 11-7/8"), with 2x3 flanges (1.5" x 2.5"). The span is a about 9' in one area and about 11' in another. 24" on center, with living room above. If anybody knows how to contact this company please let me know.