Male dogs marking territory

I set up a new gazebo this weekend in the backyard and my male mutt dog insists on peeing on it. We went thorugh this when he was about a year old when he peed on everything on the patio for about three months. No matter how much I scolded or washed it, he continued to do so. I suppose he eventually decided it was adequately marked and finally stopped doing this but now we have something new and I would really like to enjoy this without the smell of urine. Any doggy gurus out there have any idea how to fix this problem?

He is completely house trained and doesn’t have a problem when we bring new things into the house - only in the yard.

While you’re at it, would anyone like to explain why my FEMALE dog likes to mark territory?

Well, he knows the house is safe from territory challenges from other animals. Not so with the yard. He’ll get over it eventually. Also, I think the constant washing may be counterproductive. The dog’s sitting there thinking, “Great, now I’ve got to label it again. When’s that silly woman going to learn to quit messing with my stuff?” By taking his scent off, and masking it with detergent smells, you’re probably just dragging out the process.

Also, is he neutered? Intact males are more likely to have territory issues, and their urine tends to smell worse, IME.

As for the female dog, some of them are just like that. My parents’ dog doesn’t mark territory unless there’s a new dog wandering around. Then she’ll pee on a few things, including and especially anything the strange dog has wet on.