Flacking occurs when the swelling and shrinking of siding occurs due moisture behind the siding is absorbed and then evaporates. Brittle paint cracks and fails under the slow strain and eventually will pull away from the woods surface. It’s imperative to locate and eliminate the sources of the moisture. If an untrained eye doesn’t correct the problem and only attempts to mask it with a poor paint finish it’s sure to rear it’s ugly head and potentially cause more damage. These areas and their tremendous amount of vapor are very destructive. There could be a potential leak in the eaves, roof or plumbing and should be inspected further.