What Happens Before Your Slab Is Poured
If you are building a home in Central Texas there is a good chance your foundation will be a post tension slab. Here is what the crew does after the plumbing rough in and before the concrete truck shows up. This is the work you want to see done cleanly and correctly.
Form with large gaps needing backfill before pour.
Form the footprint
Carpenters build the temporary wooden frame that defines the exact shape of your slab. They set boards to the final floor height using a laser and brace them so they do not bow when heavy wet concrete pushes against them. Corners are checked for square and any steps or ledges for porches and garages are formed now.
Prepare the ground
Inside the forms the team compacts the soil, especially where plumbing trenches were backfilled. A firm, level base keeps the slab from settling. A pest pro treats the soil for termites. Then the crew rolls out a plastic vapor barrier across the entire area, overlapping and taping seams and patching any holes. This layer helps block ground moisture from wicking into your slab and flooring later.
Place any required rebar
Although a post tension slab relies on steel cables, engineers often call for some rebar at edges, corners, or around openings. Workers set these bars on small supports so they will be inside the concrete, not sitting on the dirt. Bars are tied together so they cannot shift during the pour, and any vertical ends are capped for safety.
Grid of post tension cables around the front porch of home.
Lay out the post tension cables
You will see plastic coated steel strands, called tendons, uncoiled and arranged in a grid. Anchor plates are fixed to the inside of the forms at both ends of each tendon. The crew routes the cables per the engineer’s plan, usually every three to four feet in both directions, and gently curves them around plumbing as needed. Cables rest on plastic chairs so they sit at the correct height within the slab. The live ends stick past the forms for later tensioning.
Secure and straighten
Installers lightly snug the cables to remove slack, confirm anchors face the correct way, and tie crossings to the chairs so everything stays put when workers walk the deck. They check clearances so cables are not too close to edges or corners and verify the spacing matches the plan. This is also when they mark cable ends for later measurement during tensioning.
Final checks before concrete
A pre pour inspection confirms the work matches the engineered drawings and code requirements. The inspector looks for compacted soil, intact vapor barrier, termite treatment, correct cable count and spacing, proper supports, and plumbing on test. The crew cleans debris from inside the forms and pumps out any standing water. Once approved the site is ready to place concrete.
What happens after the pour
When the concrete gains enough strength, usually within the first week, a specialized crew uses a hydraulic jack to pull the live ends of the cables to a specified force. The wedges at the anchors grip the strands and lock in the tension, placing the slab in compression. Excess cable tails are cut and the anchor pockets are sealed.
What you can watch for
Straight and well braced forms. Firm ground and a continuous plastic barrier with taped seams. Rebar off the soil where required. A neat grid of plastic coated cables on chairs with no sagging runs. Anchor plates at the edges and clearly marked cable tails. A clean, organized work area and a passed pre pour inspection.
When these steps are done right your post tension slab will be ready for a smooth pour and reliable performance on Central Texas clay soils for years to come.