Complex sentence: These beams were extended over the street, hence enlarging the footprint of the upper floor then enclosed with latticework and roofed also with wood since it is lighter as the projection is cantilevered and does not bear the weight of traditional building materials.
Split into simpler sentences: These beams were extended over the street, enlarging the footprint of the upper floor. The projection is cantilevered and does not bear the weight of traditional building materials.