I often hear people ask for a waterproof rug pad. The closest to this is a waterproof pad made for under wall to wall carpeting. Even in this case, the waterproof aspect is still not a guarantee and could cause problems by trapping any moisture between the carpet pad and the carpet above it. In the world of area rugs, although there technically is no 100% waterproof rug pad, there is something that comes close.
For those who experience the occasional spill or perhaps pet accident, no matter what type of floor covering or protection you have in place, it is always best to try to blot the area as soon as possible. When you place an area rug on your hardwood or laminate wood floor, you should have the proper rug pad. Many of these pads do not resist water or liquid at all, hence causing the spill to go through the rug and the pad right to the floor under it. The only padding available with a plastic layer is one made for wall to wall carpeting and would be severely dangerous if used under area rugs as the plastic layer is quite slippery and causes rugs to slide right off.
There is a high quality rug pad made of a recycled jute and rubber combination. This pad is about 1/4 of an inch thick and very dense. Not only is ti one of the best protections for your rugs and your floors for normal wear and tear, it is also one of the only rug pads that will resist liquid until you can get to it and dry it up.
I have tested several pads by pouring a cup of water and watching the results. this above mentioned pad did the best in as far as the time it took to penetrate through to the wood floor underneath. Since we all would like to catch the spill or accident as soon as it happens, sometimes this is not possible. This jute and rubber carpet pad resists as best as possible and takes quite long to penetrate through to the rubber bottom. Although the top jute may be wet, and this can be dried up when you have a chance, the solid layer of rubber underneath acts as an excellent barrier between the spill and your floor. I will not say the spill will not eventually seep through this rubber. It will, depending on the amount of the spill, yet in my test it took several hours for the underside of the rubber to feel damp.
As I always mention in my articles, when I refer to this jute and rubber combination pad, I am referring to the finer one available. There are plenty where the rubber is a sprayed on latex and this will not stand the test as well. My test was on a solid rubber layer that is sewn on to the jute surface.
As much as we try to avoid spills and pet accidents, they are bound to happen. Choose the proper rug pad and you will have less worries and damage to your floors.