special relativity - Calculating length contraction at speed $c$ (not near it)

Is the Lorentz transform applicable to speeds that are lower than light only?Because I'm trying to calculate length contraction of objects moving at speed $c$ (not near it) and it turns always 0. Is my calculation correct?Please help I'm just a beginner

Suppose a 5 m object is traveling at $c$,so $$x'=x/γ$$

$$\begin{align} x&=x'\sqrt{(1- (v^2)⁄(c^2)}\\ x&=5\sqrt{1-1}\\ x&=5\sqrt0\\ x&=0 \end{align}$$ Not infinite right? If so then the rule will have no length?