Why Are Post-Tensioned Slabs So Popular?

Why builders like post-tensioned slab foundations 

Post-tensioned slab foundations first became popular among the larger production builders. Today, they are used almost universally by builders of all sizes. The reason is simple: post-tensioned slab foundations are less expensive to build than conventionally reinforced slab foundations. They are less costly because the grade beams and the stiffening beams do not have to be as deep so there is less concrete used and the trenching to create the beam does not have to be as deep.

Less concrete and less labor means less cost to the builder than a comparable slab foundation using rebar. 

Why engineers like post-tensioned slab foundations

It is not obvious why Professional Engineers prefer post-tensioned foundations, but it is obvious once you get familiar with the two techniques.

To design a conventionally reinforced slab you need a soil report. The data from the soil report is used to design the foundation using various curves and graphs. Sounds simple enough, but if you give ten engineers the same soil report they will come up with ten different designs.

How can that be when they all have the same soil report and use the same graphs? Simple. They each read the graphs differently. That creates a problem: if an unhappy homeowner ever files a suit, his attorney will find an engineer who will testify that the design engineer did not read one or more graphs correctly.

Contrast that with post-tensioned design. You take date from the soil report and enter it into what is essentially a spreadsheet. Turn the handle and you have your design check without reading a single graph. All ten of the engineers gets the same answer.  

Why home buyers really shouldn’t care

Conventionally reinforced and post-tensioned slab foundations are both adequate design methodologies 


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