Q: We are installing a lift in a church that has a prestressed, precast concrete elevated floor. Concern has been expressed about cutting an opening in the floor to install a lift. Can a precast hollow-core concrete floor be cut? Any instructions to make this safer would be greatly appreciated.
A: This type of floor can be cut, but you are wise to check into things before doing so. The best approach would be to contact the producer who supplied the floor for guidance. You’re dealing with an engineered, structural system that assumes certain things about the supports and continuity of the floor panels. The original producer would know what these assumptions were and how to accommodate your needs. Alternatively you could hire a consulting structural engineer.
Precast producers do provide reference materials for their products. For example, Spancrete provides guidelines for cutting small penetrations (up to 10 inches) on the Web at www.spancrete.com/pdfs/spanNotes/spanNotes9.pdf. It includes hints on planning the cut and the very important note that you should not cut reinforcing strands without permission of the manufacturer unless shown on the approved shop drawings. If you were talking about a small hole to accommodate a hydraulic cylinder, that might be all the guidance you would need.
But when you say “lift,” I imagine you’re talking about an elevator. That will obviously require a hole larger than 10 inches. And in that case, an engineering analysis will be required.