Sorry for asking a basic question but this did not get answered on M.SE.

Let $\Omega \subset \mathbb{R}^n$ be a Lipschitz domain. How do I show rigorously that $$\int_{\partial\Omega} \frac{1}{|y|^{n-2}} dS(y) < \infty$$ where $dS$ is the surface measure.

My problem is that there is no easy way (for me) to convert this integral via chart maps etc because it's a Lipschitz domain (and not a graph which would be easy). If the integral were over an open subset of $\mathbb{R}^d$ (i.e. a normal integral) then it's easy to show using polar coordinates.