FAQ

What is hollowcore?

Hollowcore is a prestressed concrete slab with continuous voids provided to reduce weight and cost. Hollowcore is primarily used as a floor or roof deck system.

How is hollowcore made?

Hollowcore slabs are produced worldwide using a variety of manufacturing processes. PBC has chosen to use an extruder production system developed by Technocore. This state-of-the-art system is a dry cast, extrusion process where zero slump concrete is forced through the machine. The cores are formed with augers and tubes with the concrete being compacted around the cores using high frequency vibrators.

What are the benefits of hollowcore?

Hollowcore slabs provide economical, efficient floor and roof systems. Structurally, a hollowcore slab provides the efficiency of a prestressed member for unsurpassed load capacity, span range, and deflection control. In addition, the grouted slab assembly provides a basic diaphragm for resisting lateral loads. Excellent fire resistance is another attribute of the hollowcore slab system. Used as floor-ceiling assemblies, hollowcore slabs have the excellent sound transmission characteristics associated with concrete.

Will the hollowcore provide a perfectly smooth surface?

Hollowcore slabs will be cambered as with any other prestressed flexural member. The amount of camber is affected by span, pre-stressing forces, concrete differences and curing variations. PBC recommends that the erector adjust the bearing elevations and level adjacent slabs to minimize the camber differential. Also, as with any structural concrete component, minor imperfections in the surface should be anticipated.

What is done to finish hollowcore at the project site?

The top surface can be finished with a structural, composite concrete topping or by simply ‘feathering’ the joints with latex cement. We do not recommend carpet direct. The underside can be used as a finished ceiling as installed, by painting, or applying an acoustical spray.

What needs to be done to finish the openings?

Plant provided openings are ‘rough openings”. If openings through the hollowcore slabs are to be left in an exposed condition, others may provide concrete patching or trimming of the opening with another building material.

What needs to be done for openings less than 100 square inches?

Holes smaller than 100 square inches should be core drilled by the trade requiring them after the slabs have been erected and grouted. The drilling should be done only with the express written approval of ‘PBC’ engineering department.

How is the hollowcore erected?

Hollowcore should be erected by personnel skilled in such work utilizing lifting devices and cranes capable of safely handling the slabs. The slabs are to be positioned and connected to the structure in accordance with PBC hollowcore drawings and details. The slabs are erected one at a time with slings and spreader beams specifically suited for hollowcore. 

How is hollowcore connected to my building?

There are numerous methods to connect the hollowcore slabs to the building frame. The type of connection is dependent on the building material the hollowcore bears on or connects to. PBC has a library of cost-effective connection details for concrete, masonry, steel and precast concrete construction. You may request for technical manual for further information on connection, load and other details as required.