Suppose a two-storey timber cottage has been left unoccupied for 15 to 20 years. The entire structure is wooden, including all beams and supports, with a rammed earth foundation. It's situated within a small stoney clearing in the outer skirts of a broadleaf temperate forest, with alternating cool/dry and wet/warm seasons and relatively high periods of humidity - think temperate forests in central China. The clearing is surrounded by tall trees which allow in patches of sunlight, but there is little undergrowth in the area beyond ground cover shrubbery. There are streams that run through the forest, but they are seldom prone to flooding.
Regarding the structure itself, it is rather small and dingy. Windows are paper-paned and shut tight. The roof is built from clay tiles, and from straw for a porch. The floors and walls are all wooden, and so are all furniture and appliances, with some iron and bronze present. Upholstery comprises rough woven textiles such as hemp and bamboo, and some cotton and fur. The house was well-maintained prior to abandonment, and has not been broken into by humans or animals over the stated period (bugs and small scavengers notwithstanding).
Given the above, what would be the condition of the cottage, externally and internally, following the period of vacancy, in terms of structural integrity, takeover by vegetation & critters, degradation, etc.?
EDIT - A few more details: The geography/climate of this setting draws heavily on temperate Eurasian forest ecosystems, with yearly temperatures averaging from 3 to 16 degrees Celsius. Snowfall is unlikely at this particular altitude as the climate is generally mild to humid, and winters would be dry.
The cottage's design combines elements of Zhou- to Han-dynasty housing styles for the lower classes (thus the heavy reliance on wood and the rammed earth slab foundation, even though a crawlspace might be expected instead).
I understand that break-ins are practically unavoidable IRL, so I should clarify that there would be Plot Reasons(TM) justifying the lack of interruptions.