Is he the only male dog in the house? or for that matter they only dog? Males do hike their legs to mark their territory. Especially if there are other dogs in the house. And neutering does not always solve this problem
If you neuter early on (about 5 - 6 months of age) you have a good chance of having a dog that will never mark. But, of course, there is *some* chance that he still would. Bosco does not mark even when he is around other male dogs with ONE exception - in my parents living room. LOL we have to baby-gate that area off!!