This is for the level titled "Clean the Bungalow" that is a nice one story house.
There are
4 gutters on this house that you'll need to avoid
completely cleaning until they're the last 4 times needed. It's fine to hit them a little with the power washer just as long as you don't fully clean them. You'll know they're not completely clean because when they're the last to clean they'll show up on the left-hand side in the list of items "to-do."
1. The first gutter is on the front left of the house (looking at it from the front)2. The second gutter is on the front right of the house3. The third gutter is on the back right of the house (looking at it from the back)4. The fourth gutter is on the back left of the house It should be fairly easy to avoid fully cleaning these gutters as you make your way around the house cleaning everything else. Be careful when cleaning the roof to avoid getting a large piece of the gutters.
Once you're down to "posts" you'll need to clean it'll likely be these wooden pieces that are near/behind the gutters. Just be sure to use the narrowest nozzle in order to get the edge of these posts.
Note: I didn't use any special soap for this clean and only used the extensions for the base power cleaner to hit the underside of the roof from the ground.
With all that said, once you get just the gutters to show on the "to-do" list, and make sure it's 4, once you fully clean these the achievement will unlock. Congratulations! Let me know if there's anything to improve the solution and I'll add it.