Garage attic storage and weight issues...

themps

So I have a garage with king post trusses. Trusses span about 18-20 feet and they are 24 inches apart. The design is the first one at the top of this image http://images.search.yahoo.com/image...cjb3&fr=opera2

The upper chords are 2x6, the bottom chords and post are 2x4. I plan to put 3/4 osb board for storage. And the peak is probably 5 feet or so. Does anyone think this will be a problem? I don't plan on anything really heavy but the osb must weigh 60-70 pounds a piece and I weigh 250. So I don't want to over load the thing if I'm up there and the stuff is up there. Won't be too much large plastic bins full of old clothes that kind of thing. No insulation and it is supported the walls themselves as the garage has no drywall, just typical 2x4 framing. It was built in 1980....

Help please????

joecaption

It's not designed for storage. If it was the bottom cord would have been wider.
Adding full length 2 X 8's joist would be the way I would go.