We have a four year old husky that we adopted from a rescue sheltre when he was 1 year old and he was already housetrained. We never used to have problems with him since we were always very good about letting us know when he had to go outside. A little while ago when I came home one day I saw that peed in one of the room soon the second floor. When never use the second floor and the two of the rooms up there are basically empty. We cleaned it up as well as we could so that the smell would be gone but ever sine then we'll discovered that he's either pooed or peed, or both in that room. It happenes about once a week or so and sometimes a few weeks will go by without an accident. It not at night either, it's usually in the middle of the day. We always make sure to let him when he needs to go or after he eats and I haven't noticed anything that could be causing this. Since we never had to housetrain him before I'm sure how to deal with this.
Any ideas? :confused:

Sometimes they will act up for attention. If it doesn't appear to be physical/medical he may be doing it for attention. Try confining him again, like re-training him using the crate method of training. You will also need a very good cleaner to break the scent out of the area of his choice. Sometimes mixing with vinegar helps.