A friend of mine has a brittney who is around 4 years old. He never got him neutered. Up until a few months ago it was never an issue, but this summer he began to want to run straight to my brand new sofa and pee on it as soon as he hit my door. This was easy enough to explain, or so we thought, because one of my dogs had had an accident there a few months before. I just would not let the dog in th3e house. Fast forward a few months and now my friend goes to live with his girlfriend who has a house where there has never been any animal pee in the house. New sofa, new carpet, etc. The dog would pee on the front door, the sofa, the carpet, everywhere. Now it is running to the neighbor's house and peeing on their deck.

Does anyone with experience with dogs have any good theories as to why it suddenly became an issue?

I had a chessie that started peeing all the time and turned out it was cancer causing it.

Infection?

That usually only happens to dogs that don't have a kennel or a tie out chain. It should not happen a second time unless the owner wants it to.
Did this person offer to replace your furniture?

Maybe the dog dislikes certain types of furniture or people?

It is an obvious territorial issue.

I would have her visit the vet first. Could be medical condition. If not, retraining may be needed, good luck!

That's not good at all, med checkup first then consequences should begin and escalate until they work....don't work?....snip, snip.

I had a cat doing the same, it turned out to be a bladder infection. In my cats case it was caused by high sugar content in the urine due to diabetes, but being 4 years old I assume it's not likely your dog would have it.

Not worth the cost of ruining the house, it would not be allowed in my house

I have a dog in the house story:

A rich doctor wanted a very tough german shepherd. Paid for me to go to Europe and find him one.
I told him that type of dog may be hard to handle and would need to be taught who was the boss....I emphasized this to him and he agree that he could do this.

I bring the dog back and he meets me at the airport, we get the dog out and let him go for a walk and head to the dr's house. His wife has a meal waiting for us on the dining room table...dr walks the dog into the house on leash and lets is off leash once we get inside. Dog checks out the house....he was well housebroken and very clean in his kennel so no peeing problems....dog jumps up on the table and starts eating.....


Dr looks at me and asks what he should do, I said we talked about this......
In the end he swapped for a dog I already had before he sent me to Europe, Ordi, a great Hungarian German Shepherd.

I will send him to the vet.

I agree, I would have performed an autopsy immediately.

Diabetes is another concern. But a telltale sign is they drink a LOT of water. Diabetes is pretty common in dogs as well. That requires 2 insulin shots per day...Which in turn gets both the water consumption and peeing under control better.

Doing that on command, not all the time, sounds more like territory marking.

I don't have a brittany, but if it's not medical I'd start over by leash/treat training the dog as if it were a puppy to go "potty" outside in a designated area. Even if the dog doesn't have to go, I'd take it out frequently. New smells new area pretty common as stated.

Sure what it sounds like to me.

I'd get a female! Problem solved.

I see that.

Prostate?

When I was with my ex I had 2 male shorthairs and she had 5 or 6 female German shepherds... my males had pee wars with each other inside the house, mostly on the couch, but also on hallway doors, cabinets, etc... I broke up with her, moved out and it was never an issue again. Not sure how this relates to your friend's situation but it could be good info for someone in the future haha.