When placing a block on a carpet it floats above the carpet

I placed down various colored carpets to make my house look nice, but when I tried to place a fence post, to hold my horse, the fence post seemed to float as if the carpet was a full block. I tried it on all the other colors the same happened even if I used a different block. Water and lava seemed to act similar. Redstone, string,levers pleasure plates and other items also floated in a similar matter. This defeats the purpose of carpeting.