Originally Posted by
Amt0571
The garage is ventilated by an unused chimney that was left open precisely for this reason. I have checked and so far I haven't seen any condensation on the bikes. However, I hanged them on the wall by the front wheel in summer using hooks, and when it started raining a few weeks ago, one of the humid spots appeared below the hooks. As I said it just feels humid to the touch. There's no water dripping or even reaching the floor, and nothing more than the back tire of one of the bikes is touching the humid part of the wall.
It seems that before I bought the house, the neighbour built a wall in his patio against my garage wall, but it doesn't reach the top of my wall and water filtrates between them. It doesn't help that the garage is not really well built and is totally uninsulated. Since the house was unhinhabited at that moment, nobody complained. It's not the friendliest of neighbours, so I don't have faith that it will be resolved quickly.
...if you think that this intersection between his short wall, and your taller garage wall is the source of your moisture issue, is there anything preventing you from extending your roof overhang on that side ? You can extend it far enough by tying onto the existing rafters. It will cost you some money, but I think you'll have trouble getting an uncooperative neighbor to tear down an existing "improvement".
Otherwise, you might be able to work out a slanted watershed structure that runs along the top of his wall and ties into your garage wall, which would probably be easier to build, because you don't have to do it up on ladders. But I really think you can improve your situation a lot with a blower in there somewhere. The chimney alone is not enough, unless you have some sort of intake opening down low, like vents in the bottom of one wall, or locking the garage door in place with a small 4" gap between the bottom of it and the ground.