NC Pipe & Drainage
Oldcastle Precast, Inc.
1431 Products Rd.
Fuquay-Varina NC, 27526
Phone: (919) 552-2252
Fax: (919) 552-1310
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Knowledge Center

FAQ 

 

How far can Hollow Plank span?

Under normal conditions, 6" plank can span 20'.  8" plank can span up to 30'.  10" plank can span up to 35'.  12" plank can span up to 40'.  And 16" plank can span p to 50'.

 

What is Camber?

Camber is inherent in all prestressed precast products.  It is the upward deflection created by the prestressed forces in the strands located below the center of gravity required to resist design loads.  Camber cannot be designed to an exact number.  Planks with dissimilar lengths, differing strands patterns, or openings adjacent to each other will have differential camber.  The benefit of camber in prestressed precast products is that it allows for longer spans, shallower depth sections, and higher load carrying capabilities than could be achieved with conventional building materials.

 

How are load tables interpreted?

Load tables show the span length in feel across the top, and the plank series along the left hand side.  The series indicated the number of strand (or wires) in the plank.  The field of the table contains the achievable loads at each given span.  Load tables are meant only to be a guide, as engineers will do actual plank sizing.

 

Can holes be cut in Hollowcore Plank?

Yes, generally they should be aligned in the plank so that the fewest number of strands is cut as possible.  All intended openings should be placed on the shop drawings during the approval process so that they can be properly design engineered.  Hold can be cut with a zip saw.  Round openings are generally core drilled by the respective trade that requires the hole.  It is important that the holes are cut AFTER the plank has been erected and the keyways grouted and cured.

 

Can attachments be made to the underside of Hollowcore Plank?

Yes, anchors can be drilled and sleeved into the underside of the plank.  Different connectors can withstand carrying degrees of pullout force.  Drilling through the plank and bolting completely through the plank can achieve heavier hanging loads.

 

Connection details are located in the Technical Guide for Hollowcore Plank?

Click Here to view more detail on this.

 

Do the ends of the Hollowcore Plank need to be filled solid?

In most cases, the core ends do not need to be filled.  In instanced of extremely high loading conditions or exceedingly long span requirements, solid ends may be recommended to provide additional shear strength.

 

How is the underside of Hollowcore Plank finished?

The plank underside is generally finished with a medium to heavy textured acoustical material such as USG Imperial QT or equal.  It is recommended that a Block Filled be applied as a prime coat, (i.e., Pittsburg Paint PPG6-7, Latex BF, Benjamin Moore 28501) prior to the application of a sprayed textured acoustical material.

 

How is the topside of Hollowcore Plank finished prior to flooring application?

Plank can be finished with a minimum ¾” leveling, such as a gypcrete.  A 2” + structural concrete topping may also be applied.  (This is 4000-psi concrete that must be steel mesh reinforced.)  The type of topping for each application depends on the finished flooring material to be used.  When planning for a topping slab, there are a number of design considerations: camber, floor decks in which planks change direction, elevations of door openings, etc.

 

Is a structural topping necessary?

In an instance where a structural topping is required, a minimum of 2” of reinforced concrete designed for a 28-day strength of 4,000 psi must be specified.  The top surface of the plank must thoroughly be cleaned and properly prepared prior to the placement of the topping slab to ensure proper composite action.  The reinforcing wire mesh in the topping slab is to be determined by an architect/engineer.  (Note that 2” minimum thickness is measured at mid-span, or high point of camber, therefore additional concrete may be required at the perimeter.)  All non-load bearing walls (CMU, Steel Stud or Wood Partitions) should be installed AFTER the concrete topping is placed.

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