First we study in detail the tensorization properties of weak gradients in metric measure spaces (X, d, m). Then, we compare potentially different notions of the Sobolev space H 1,1 (X, d, m) and of weak gradient with exponent 1. Eventually we apply these results to compare the area functional ´ 1 + |∇f | 2 w dm with the perimeter of the subgraph of f , in the same spirit as the classical theory.