I have a small two-step 2 deck that comes off my sunroom, and due to the location, the deck never gets any sunlight so it's almost perpetually damp/wet during rainy spring and summer, making it the perfect place for a carpenter ant colony.
The sunroom itself is supported by short pressure treated 6x6 posts going onto concrete bases, and these get damp from time to time if the rain is heavy enough.
I plan on replacing the ant-infested deck with composite decking, but since the stringers will be made of wood, they are just as susceptible. There is also an exposed wood face as the final step up to the sliding door of the sunroom that is perpetually damp.
Aside from the composite boarding on the horizontal surfaces, how can I protect the other wood surfaces from carpenter ant infestations?