Complex sentence: Simpson and Eaton seize the occasion to each add a third floor to their store; the adding of a third floor did not necessitate any change in the outdoor architectures of Simpson and Eaton because both stores were built to house three floors back in 1965.
Split into simpler sentences: Simpson and Eaton seize the occasion to each add a third floor to their store. The adding of a third floor did not necessitate any change in the outdoor architectures of Simpson and Eaton because both stores were built to house three floors back in 1965.