You’ll have to look at your covenants. Different HOA’s have different rules and regulations, and, when you bought, you signed on for all of them. Covenants should’ve been provided to you when you purchased your home, and they’ll outline any restrictions on what is/isn’t permitted. They’ll also explain the procedure should you decide to improve your property (build a deck, fence, etc). I can tell you that our HOA board members don’t wander through our yards. If they notice something when they’re out in the neighborhood or if another neighbor complains, a resident might get a letter. Maybe other HOA boards are a little sleuthier with more time on their hands?