I have a large piece (13'x15') of high quality nylon carpet that I would like to make into a rug. I have a very specific question about padding and protection - I'd like for the rug padding to have a moisture barrier, provide comfort, and be relatively inexpensive.

Is it as simple as ordering more of the dense padding I used underneath the carpet in my bedrooms, and then gluing or otherwise applying it to the back of this large rug? I would think so, but how far from the edges of the rug I should stop the padding? Or is there a better product that would help me achieve the comfort and protection for my hardwoods underneath? The waffle weave rug pads that are everywhere seem to offer a grip to keep a rug from sliding or shifting, but I don't need that as each end will be anchored by very heavy pieces of furniture.

There's two other pieces that I'd like to bind together for a runner for the hall. I watched a good YouTube video and it seems doable. A solution for adequate padding has me stumped, though. Thanks.