Instead of toenailing 2x4's between the ceiling joists I would lay them right on top. You don't want to compress the insulation, that compromises their ability to insulate. Also limit the weight of anything up there including any flooring because those joists are probably not rated to take a lot of extra load besides the ceiling.

Hendricus, are you suggesting screwing the pieces on top of the current joist because it is easier than toenailing the cross piece? Would that mean I would have to put in a lot more pieces to make sure the plywood sheets would be stable and level?

I want to apologize up front because I am really new at this kind of thing. I will take out my drill press, band saw, jigsaw, etc. for all kinds of projects, but have really never done anything like this. I've taken woodworking classes and made "projects" (jewelry boxes, crown molding, etc.) but this is the first kind of home renovation project I am going to attempt. I'm thinking it would be pretty simple...am I delusional?

Hendricus, you mentioned joists. How can you tell? I've tried reading some things but I am confused about some of the terminology, namely truss vs joists. When the writers then start adding in rafters, girders and beams, my eyes start to cross. LOL

When you mention weight on joist, in general what are we talking. I am talking about using the big plastic containers that will probably weigh about 30-45 lbs each and I was planning a dozen plus lots of luggage (empty) up there. Would that be too much on the joists?

sonepi-
Whatever you do, use screws, not nails. If you start pounding on the joists with a hammer, it will transmit the vibrations to the sheetrock, and you may find cracking around the fastener heads for the ceiling below. You don't want to add sheetrock repair and repainting to this project...

In order to determine if the attic floor joists (the horizontal wood members that hold up the plywood attic floor and are now covered by insulation) you need to tell us the size of the joists, the space between them, and the distance they span (usually from the outside wall to an interior bearing wall near the center of the house). Usually attic joists are designed to support no more than 20 lbs/s.f. so a pair of joists could support 400 pounds if the middle 8 ft of the joists were covered by flooring.

Unfortunately, it appears the roof rafters have braces that transfer loading from the rafters to the attic joists (or vice versa) so the structure is more complex.

Anyway, adding too much load to the attic could cause the ceiling below to sag and crack and doors might eventually bind in their frames.

You might just add some 1x10 boards along the sides of the current attic floor area to allow a bit more storage. Go into the basement and see if there is a beam down the middle of the house on posts. See if there is a wall above that beam on the upper floors. If so, the the attic joists would be supported on that bearing wall. Attic loads above and reasonably near the line of that wall will not be a problem.

This is something a competent carpenter would be able figure out with little effort but if you enjoy doing things the hard way and taking risks go for it.

This attic was not designed for storage. Not only are you inviting structural and cosmetic problems in your home, but the attic may be swirling with snow in harsh winters and humidity in the summer--maybe not ideal storage.

Rafter are the 2x4's or 2x6's that you see on the underside of the roof.

Joists are what you are sitting on, they hold up the ceiling and the floor in the attic goes on them. They will run in the same direction as the rafters.

Brush a little of the insulation aside under a rafter and you will see a joist.

Good idea on the 1x10 boards, you can just lay them in the attic accross the joists. A couple of screws to keep them from shifting.

I hate the large plastic containers, they're a good way to get hurt. Use smaller containers and spread them around.

Thanks you so much everyone for your responses. This is exactly the information I was looking for to help me determine if this is something I want to try.

Kudzu9, I was definitely planning on using screws, because I'd read somewhere that over time they could work themselves out. I did not know about the vibration of hammer and nails doing damage. Thank you for that info.

Macy, your information of the details I would need to know to determine if this was feasible was just what I was looking for and thank you for explaining it so clearly. I had to chuckle at your comment, "... if you enjoy doing things the hard way and taking risks go for it." Are you my husband's twin? ;-)

Worthy thank you for the pointers, I really never thought of it causing structural problems. Hendricus, I appreciate you taking the time to explain rafters and joists.

I love this forum (all areas) because you all brought up things I had not considered. With all the wonderful suggestions, information and pointers, I will either have someone come take a look to see if it is feasible (and let them do the project) or better yet, I will just store my items somewhere else. It just would have been nice for it to be up and out of the way.

Thanks everyone.