Because floor joists are close to the ground and untreated wood is susceptible to rot, warping, and damaging pests, we use lumber that’s been properly treated to avoid these problems and ensure longevity. Its insect and fungal resistance also help it to outlast natural wood, and because it tends to be denser than untreated wood products, it also has increased strength.
We use 2×4″ pressure-treated floor joists on our 8′ and 10′ wide sheds and 2×6″ pressure-treated floor joists on standard 12′, 14′, and 16′ wide garages.