Flir can show you where a wall/roof is damp, as that part stays cooler, due to evaporation.

However, the standard method for finding leaks, cars, boats, trailers, buildings, whatever, is begin hosing at possible entry-points from the bottom, up, so that the beginning of leaking identifies which height the leak was at.

If it's taking awhile to get through a wall, though, you might want to, say, hose the lowest 1/2m of the closest-to-the-right-edge of your 4 walls, then come back in awhile, getting some other area(s), maybe keeping a rigged sprinkler going on it?

Getting the things, to stomp the leak, is important, eh?

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