Post-Tension vs Conventional Slab

The difference

• A conventional slab is reinforced with steel rebar cast into the concrete.
• A post-tension slab contains steel cables that are tensioned after the concrete cures, putting the slab into compression so it resists cracking as soil moves beneath it.
• Post-tension is extremely common in Central Texas homes built from roughly the 1980s onward, precisely because it performs well on expansive clay.
• Both can be repaired with piers. The critical difference is what happens if someone cuts into the slab.

Why it matters before anyone cuts

• Cutting or coring a post-tension slab without locating the cables first can release enormous stored tension. That is dangerous to the person doing it and damaging to the structure.
• Any competent contractor scans to locate cables before coring a post-tension slab. This is standard practice, not an upsell.
• It comes up more than homeowners expect, because plumbing access under a slab often requires coring - a common part of foundation and plumbing work.
• If a contractor is casual about which slab you have, that tells you a great deal about the rest of their process.

How to find out which you have

• Look for a stamped notice, often in the garage or at the slab edge, warning against cutting.
• Check your original builder documentation or the plans if you have them.
• Your municipality may hold the original permit records.
• A foundation contractor or engineer can determine it during inspection.
• If nobody can tell you, that alone is reason to slow down before any cutting begins.

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