Complex sentence: The building's exterior roof is fully supported by the brick walls, thus the loft is an entirely open space save for some pole and beam construction supporting the laminated beams, which act as tie rods at the base of the roof.
Split into simpler sentences: The building's exterior roof is fully supported by the brick walls. The result is a loft which is an entirely open space save for some pole and beam construction supporting the laminated beams, which act as tie rods at the base of the roof.