The 3-4-5 method is more accurate than a framing square at scale

For layout of foundations, decks, or framing, the Pythagorean theorem (3-4-5 or multiples like 6-8-10, 9-12-15) provides greater accuracy over long distances than a framing square, which amplifies error at scale. Diagonal measurements between corners must match before pouring concrete. This is standard practice per the ACI 117 tolerance standard for concrete construction.