Beyond the Build

Tips from the Field

Pros and Cons of Three Concrete Structure Methods

Over the years, we’ve built parking structures that employed different structural framing methods. The system chosen depended on a variety of factors including land/site constraints, design functionality and accessibility of local resources.

Cost is a variable of all of the above. At times, the value of the land exceeds the price to add vertical to a project, similar to underground retention. Our experience has shown that each method has its own characteristics that can make it the correct application for a particular project.

7-12-13 Composite slab on metal deck


  • Form work is minimal.
  • There is no leveling or topping slab required.
  • Floor flatness and levelness can be a challenge. Due to overload on decking formwork, super-flat floor requirements may be unattainable.
  • For safety concerns, work that can be completed underneath unfinished floors can be minimal.
  • Occupancy requires thermal insulation between non-conditioned space below. This can be accomplished by spray-on application.
  • Fireproofing of steel members is required. 
  • In the long term, painting of surfaces can become a maintenance expense.

Post tensioned



  • Super flat Ff numbers are possible.
  • All deck work is formed in place, requiring large resources of forming materials, shoring scaffolds and labor.
  • The location and count of post tension cable is a must.
  • Progress is much slower than other types of decks.
  • Time must be spent waiting for concrete to reach 70% of design before cables can be stressed and shoring scaffolds/ formwork can be removed for next lift.
  • If the space below the post tensioned slab is parking, a topping slab and insulation are required between conditioned space.
  • It is not as cost effective if a project only consists of one or two elevated slabs.

Cast in Place



  • First and foremost, installation is much faster.
  • Super flat floors are possible.
  • No fireproofing is required.
  • No forming is required, except for leveling and a topping slab.
  • Larger lifting equipment is needed for the loads of precast. This requires more stable soils or mats to support the crane.
  • It is necessary to level the slab.
  • Insulation is required between the topping slab and the leveling slab when used with conditioned spaces.
  • Can require slightly larger foundations due to loads.


Merrill Stewart Jr.

Merrill Stewart is Founder and CEO of The Stewart/Perry Company, a commercial building contractor based in Birmingham.