The term “Q-Deck” has become synonymous with many different types of decking much like the term ‘Kleenex’ has come to be known for any type of tissue paper.  The answer in this case though is a common misconception among contractors and engineers.  Metal floor and roof deck is available in many types, heights, and thicknesses but builders that use the term “Q-Deck” often are not sure what type of deck they are talking about.  The truth is – there is no such thing as Q-Deck!  Our research has determined that the term “Q-Deck” most likely refers to the Robertson “Q” decking series manufactured as far back as the 1960’s.  Unfortunately though, this description has now come to be a generic description of any type of metal deck.

Instead of looking for Q-Deck, contractors should reference deck by it’s more proper nomenclature.  If there is no design document available, the contractor needs to know the specific function of the deck in addition to its required height and span before placing an order.  To help them narrow down their choices though, here are the most common types of deck that are typically used in construction:

ROOF DECK:

Metal roof deck can be specified as either Type B or N.  Type B has 1 ½” high ribs while Type N has 3” high ribs and can span up to 17 feet.  In our experience, we recommend galvanizing all roof deck with at least a G60 or G90 level depending on its exposure and use.  When using cementitious insulation fill in the flutes, we also recommend using a vented deck.

Roof_Deck

 

FORM DECK:

Form deck is used as a stay-in-place form system for elevated concrete floors.  The strength of the form deck does not contribute to the final load carrying capacity of the floor system – only to support the weight of the wet concrete during pouring.  The concrete itself must be designed to carry the permanent weight of the concrete plus live loads.  Shoring may be required for longer spans with this type of decking.

 

Form_Deck

 

COMPOSITE DECK:

Composite deck is used in conjunction with the strength of the concrete to develop a composite system.  Embossments in the vertical ribs will bond to the concrete to develop the composite action.  Shoring may also be required for longer spans with this type of deck. A commmon question comes up from time to time regarding whether to turn the wide ribs up or down.  The deck capacity changes very little in either configuration.  When shear studs are used on the beams, with the wide ribs turned down, higher capacities are obtained, due to the increased section properties of the concrete section.   If no shear studs are specified we recommend to turn the narrow ribs down in order to save on concrete.  The reduction in capacity is negligible.

Composite_Deck

 

Understanding how to properly specify metal deck is just one of the ways engineers and contractors can learn to work together on the same page.  To see some other ways Allegheny Design Services is serving contractors, check out some of our most recent Projects.

Written by David Simpson, P.E., SECB, MBA, President, Principal Engineer

dave-simpson2David Simpson’s experience includes over 30 years in structural design and project management for industrial, commercial, institutional and nuclear/chemical facilities utilizing steel, concrete, masonry and wood. His accomplishments include design and construction administration of health care facilities, hotels, schools, shopping centers, aircraft hangars, numerous retail facilities and several forensic engineering assignments. He has professional registrations in D.C., Maryland, Ohio, Pennsylvania, South Carolina, Virginia and West Virginia. Simpson graduated from the West Virginia Institute of Technology with a bachelor’s degree in civil engineering and an MBA from West Virginia University.