Post-tensioned slabs-on-ground provide a cost-efficient, high-performance solution for problems associated with ground-supported residential foundations on shrink-swell soils. The compressive stresses resist the anticipated tension stresses induced by the soil movements, enhancing the performance over a non-prestressed foundation. Cost benefits are achieved by reductions in quantities of concrete, steel and excavations, which in turn reduce labor costs.

In less expansive soils, a uniform thickness foundation is utilized. Typical thickness ranges from 7.5- to 12-inches and any increases in material quantities are compensated by reductions in labor and equipment costs. With the elimination of stiffening ribs, a post-tensioned foundation can be constructed rapidly eliminating labor and equipment to dig the ribs and dispose of excavations. This is a substantial benefit in sandy soils where trenches require shoring. Post-tensioned foundations are also used in areas with stable soils to reduce cracking, reduce or eliminate control joints, increase flexural capacity and improve constructability. Reducing the control joints also improves the serviceability and eliminates durability problems.

Advantages of using post-tensioning for your next slab-on-ground project:

    • Stronger/more efficient: Less concrete and steel are needed for the same structural capacity and the slab stiffness is increased so that the slab is better able to resist bending caused by differential soil movements.
    • Minimizes and Controls Cracking: Post-tensioning will reduce cracking and keep any cracks that might form tight, preventing entry of insects and reducing possible water penetration, which can damage flooring and cause mold problems.
    • Controls deflections: The strength and added stiffness of a post-tensioned foundation reduces the amount the slab will bend under load.
    • Faster Installation: With fewer pieces to handle and less concrete to place, a post-tensioned slab can often be installed more quickly than a comparable rebar- or wire mesh-reinforced slab.
    • More Reliable: An engineered solution, post-tensioning is designed to exacting standards and code requirements, has an excellent performance record and offers increased reliability.
    • Economical: Cost benefits are achieved by reductions in quantities of concrete, steel and excavation, which in turn reduce labor costs. Beams are smaller and slab thickness is less, therefore savings in excavation and site preparation are possible.

Stronger Standards, Exceptional Structures

The International Code Council (ICC) has released the 2024 version of the International Residential Code (IRC). IRC 2021 (and preceding) has a Section R506 “Concrete Floors (On Ground),” as well as a Section R506.1 “General” that has only referred to R506 and ACI 332 for the design and construction of concrete slab-on-ground floors. The 2024 IRC code change adds a new Section R506.2 “Post-Tensioned Slab-on-Ground Floors.” This adds the IRC code requirement that “post-tensioned concrete slabs-on-ground floors placed on expansive or stable soils shall be designed in accordance with PTI DC10.5.” DC10.5-19 is also added to the IRC code as a reference. These modifications to the code directly influence the construction of post-tensioned slab-on-ground (PT-SOG) structures. To find out more and keep up to date, please visit https://www.ptstrongerstandards.com/.