the expression used for "main floor" is "rez de chaussez"
You say "quatrième étage" in French to indicate the fourth floor.
Le troisième étage is third floor in French.
The tenth floor is "le dixième étage" in French.
You would say "Le sol est la lave" in French to express "The floor is lava."
"Sweep the floor" in French is "balayer le sol."
premier étage
plans d'étage
Dernier etage.
le plancher
D'appui au sol.
"On the ground floor" in French is "au rez-de-chaussée".