Regular inspection is crucial when using untreated wood in any construction project. Prevention measures should be taken to avoid decay or insect damage, which can compromise the structural integrity of a pergola or other wooden structure. It's important to inspect the wood at least once a year and after any severe weather events that may have caused damage. Signs of decay include soft spots, cracks, splits, and discoloration. Insect damage can manifest as holes or tunnels through the wood.