Building an NIC cage

So I bought the grids today to start my bunny's condo but I have a quick question, I want to make a second level, but only half of the total length if that makes sense. Is zip tieing the grids together going to be enough support with a wood floor on top of it or do I need to support it more and how would I go about supporting it without comprimising space underneath it.

Zip ties are very strong, especially quality ones. If you used a zip tie on say every other square, you should have plenty of support. You can also use wooden dowel rods to add extra strength.

Thanks! I did run into one other problem...I am not sure how to make doors or ways to get into the cage to clean... I havent technically watched any "how to" videos which I think I might have to do if I cant figure it out..

2 four inch zipties per seam between two grids is all you need. that'll support the shelf just fine, however it may sag a little without a dowel supporting it depending on the size. I zip-tied the dowels I used to the underside of the shelves.

as for making doors, for the panel(s) you want to be able to open, only ziptie one edge of them to the rest of the cage... you can use a carabiner to hold the door closed (these things: )

I like to have the doors in the middle of the cage. I also prefer them to be 2X2 grids if possible or at least 2 wide. This makes it easier to get into the cage to cleaning and to get the rabbit out when needed.
For making the doors, only zip tie one edge so it opens. You then keep the closed using clips or small bungee cords (whatever works for you). You can make the door one big door or 2 smaller doors.

I am making the cage 2 grids high, I want to use two of the top grids (ones that are right next to each other) as a door so I can get in there well to clean the whole thing when nessecary, but now I have ran into another dilema, how does my bunnies get out of the cage when I use the top two grids without having to pick them up to let them out? LOL I thought this was gonna be easier but I was mistaken, so many things to consider! I already screwed up part of the cage because the box that the grids came in some of the grids have small openings and some have larger ones and I put the smaller holed ones on the bottoms and intended to put the smaller ones also around the second story shelf but accidentally put the large ones there because I wasnt thinking clearly, so now I have to cut all those zip ties because I dont want the large holed ones anywhere they will be able to stick their head into.

I put the door in the front of the cage. This way the rabbit can come out on their own. It is easy to clean as well without needing to bend over anything.

You can put doors in multiple places if you like. The pic below shows 2 open doorways, but actually there are more doorways on that cage than is shown.

The grid just to the left of the open front door also opens. Also, the middle level front grids open. And also another grid in the middle on the far right side of the cage opens.

Basically, I just put doors anywhere I thought I needed to allow access.

If you've already zip-tied the cage, you can make a doorway by cutting the ties all around the door (except for the hinge side).

I used dowels for extra support beneath the NIC shelf, used a peg board plank over it and then a coroplast sheet over that. Made for a sturdy, easy to clean shelf. The door war is easy, no zip ties at the edges of the door frame. I used to use the clips Imbrium mentioned but found them to tricky (yes I can even screw up something as easy as that so instead I started using these paper clips Just two well placed ones can even thwart the larger escape artist buns.