Complex sentence: In 1953 they commissioned Francisco Juan Barba Corsini to construct 13 apartments in the attic, which until then had been the laundry, becoming less frequently used and an unhealthy place, filled with garbage and cast-offs.
Split into simpler sentences: In 1953 they commissioned Francisco Juan Barba Corsini to construct 13 apartments in the attic, which until then had been the laundry. However it had become less frequently used and an unhealthy place, filled with debris and cast-offs.