Norway spruce cladding panels were surface charred with a prototype device utilizing a hot plate method. The panels were used to construct a test wall that was exposed to natural weathering for a period of two years. The changes in functional groups were evaluated with photoacoustic FTIR spectroscopy. The analysis revealed degradation of the thermally modified lignin component, indicating poor stability in weathering. Improvements in the prototype device process conditions, such as increased surface pressure and slower feed speed, and future research needs regarding surface charred wood are discussed.