Reinforced concrete and post-tensioned frames each win on different jobs. Here's how span, floor-to-floor height, programme and vibration drive the decision, and where a hybrid frame beats both.
The decision comes down to four levers
Reinforced concrete and post-tensioned frames are not rivals so much as tools suited to different jobs. The right call almost always turns on four things: the spans you need, the floor-to-floor height you can afford, the programme, and how sensitive the building is to vibration.
Get those four straight early and the structural strategy usually picks itself. Leave them vague and you risk redesigning the frame at tender, which is the most expensive time to change your mind.
Span and depth: where PT earns its keep
Post-tensioning lets a slab span further with less depth. On medium-to-long spans a PT flat slab can be 20 to 30 percent thinner than the equivalent RC slab. Over many floors that recovered depth can add up to a whole extra storey within the same overall building height.
On short spans the advantage shrinks. If your grid is tight and your floors are already shallow, plain RC is often simpler and cheaper, with none of the stressing sequence to coordinate.
Programme and buildability
RC frames are forgiving and well understood by most labour teams; the pour cycle is predictable. PT adds a stressing operation and early-age strength monitoring to the critical path, which a capable specialist absorbs comfortably but an inexperienced team will not.
Vibration-sensitive uses — labs, imaging suites, precision manufacturing — usually favour a stiffer RC solution tuned to a response factor, rather than a thin PT slab.
When a hybrid beats both
Real buildings are rarely pure. A tower over an open podium may use a PT or heavily reinforced transfer slab, RC for the repetitive floors above, and precast for stairs. Choosing per zone, rather than per building, often gives the best overall result.
If you are unsure, our free RC vs PT frame selector walks through the four levers in a couple of minutes and gives you a reasoned starting point to discuss with your engineer.
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