He eventually succeeded his uncle as Inspecteur general at the Corps des Ponts et Chaussées.

He directed the construction of bridges at Choisy, Asnières and Argenteuil in the Department of the Seine, and built a footbridge to the Île de la Cité in Paris.

His 1824 design for the Pont des Invalides failed to leave a safety margin on top of his calculations, and after cracking the bridge had to be dismantled, destroying Navier's bridge-building reputation.

Navier formulated the general theory of elasticity in a mathematically usable form (1821), making it available to the field of construction with sufficient accuracy for the first time.

In 1819 he succeeded in determining the zero line of mechanical stress, finally correcting Galileo Galilei's incorrect results, and in 1826 he established the elastic modulus as a property of materials independent of the second moment of area.