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Post-Tension Slab

Also called: PT slab, cable slab

🧱 Foundation & Drainage — a term you may see in your inspection report.

What is a post-tension slab?

A post-tension slab is a concrete foundation reinforced with steel cables that were tightened after the concrete cured. They're common in Texas because they handle expansive clay soil better than a conventional rebar slab. The critical thing for any homeowner: never cut, core, or drill into a post-tension slab without having the cables located first. Those cables are under substantial tension, and cutting one is both dangerous in the moment and expensive to repair.

Why used in Texas
Handles expansive clay better than conventional rebar
How to identify
Often a stamped or placarded warning at the garage or utility area
Absolute rule
Locate cables before cutting, coring, or drilling
Common trap
Anchoring shelving, safes, or fencing into the slab

What it actually is

Steel cables run through the slab in a grid and were pulled tight once the concrete hardened, putting the whole slab into compression. Compressed concrete resists cracking far better than concrete that's just sitting there.

Why it matters in East Texas

Very common in newer East Texas subdivisions. The problem I see isn't the foundation — it's the second owner who has no idea what they have and wants to anchor a safe or a basketball goal into the garage floor.

What I do when I find one

I note the foundation type in the report and look for the identifying placard. If I see evidence of coring or drilling, that gets photographed and written up, because it's the kind of thing that needs someone qualified to assess.

What it means for you

Keep this in mind for anything you'd anchor into the floor — shelving, safes, exercise equipment, fence posts near the slab. It costs very little to have cables located and a great deal to fix a cut one.

More foundation & drainage terms: Settlement Crack · Normal Foundation Movement · Pier & Beam Foundation · Negative Grade · Moisture Intrusion

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