I have made many, many denim quilts in all different size squares. Some were rag quilts & some were not. I back all my denim quilts with fleece & everyone loves them & they last forever. I get my denim from friends & relatives.

I made one years ago for the bed in the back of our van. I just used wide seams and stitched the edges under. Only the single layer. My squares were however big I could get from the bottom part I cut off when the knees wore out in the kids jeans - probably 9" or 10".

Denim quilts were some of the first I made. I just cut them into 6" squares (I would probably do 6.5" nowadays), mixed and matched the different shades of blue and sewed together into a large throw size--almost twin size, and used a plaid as backing. I tied them. They are really cute. Still around. I made one with blues, one with blacks, one with oranges, greens, etc. (I started looking for used jeans/denim in various colors.)

Stain glass quilt with denim squares, black sashing between denim square so you are never sewing denim to denim. It is on my bucket list for my great nephew's graduation 2016. Google it and you can get a free pattern. Pictures are on Pinterest also.

I have made several of them. A tip is to use a heavy duty machine to sew it. After it gets so big it seems to put a drag on the machine. I burnt up my Elna Air Electronic machine sewing a jean quilt. The machine caught fire right as I was sewing. Scary forsure.

I know you are wanting suggestions on making a jeans quilt but just a side note for your little grandson... I recently made a LOT of bibs for various friends who were having little ones. I backed them with DH's recycled jeans and did not use batting. I even put decorative stitching around them. They sewed up beautifully and everyone loved them.

I should add they won't leak liquid easily!

I love working with denim in the longest pieces possible. You can leave the long leg pieces and cut them into 2 1/2" strips to make a quilt like a jelly roll race. Curved techniques are also nice in denim if you are interested. Keep in mind that all of your fabric does not have to be denim. The denim quilts are so heavy - I always incorporate other cotton fabrics. There are a few options on my blog if you want to search "denim" there.

I made a denim quilt for my grandson using all different sizes of blocks. I used all the jeans including zippers, pockets, etc. I backed them with a bandana type material and no batting. He used it many years mainly as a floor quilt to watch TV, do computers with friends, etc. He kept his pajamas in one of the pockets.

I would make the squares as large as possible because you can always make the blocks smaller if need be. Wow do I ever love this denim quilt. Could you please send us a link for the pattern?