Post Tension Remodel
A lot of homeowners love the idea of a true curbless shower—clean lines, easier access, and a more modern feel. But if your home is built on a post-tension slab, creating that look takes extra planning (and it affects the budget).
Recently, we completed a bathroom remodel where we converted a tub/shower into a curbless shower on a post-tension slab, and I wanted to share the approach we used—plus how the same process applies to other remodels like kitchen plumbing changes.
Why post-tension slabs change the game
Post-tension slabs contain high-tension cables laid in a grid, typically 30”–36” on center. Those cables are anchored into the slab system with plates buried in the stem wall and tensioned to extremely high forces. In practical terms, that means any concrete removal or plumbing work under the slab has to be planned carefully—especially near exterior walls—so you don’t create structural issues or, worse, a dangerous situation.
Step 1: Scan the slab with GPR before cutting anything
For this project, we brought in a post-tension specialist to scan the slab using GPR (Ground Penetrating Radar). The scan mapped the exact cable locations and depth. In this case, the cables measured about 3.8” deep, which gave us enough verified clearance to safely remove 1.5” of concrete in the shower area without compromising the slab.
Step 2: Controlled demo (handled by the post-tension company)
The post-tension company also handled the demolition. That reduced risk and simplified coordination, because the same specialists who mapped the cables were the ones doing the concrete removal.
Step 3: Use a system that supports curbless without excessive depth
To make the curbless design work, we used a Schluter Kerdi shower system. One advantage of Kerdi is that it typically requires less depth than traditional deck mud, which helps when you’re working within the limits of an existing slab. The end result was a true curbless entry with the correct slope and proper waterproofing.
How this applies to other remodels (like kitchens)
This same approach isn’t limited to bathrooms. A common example is relocating a kitchen island that needs plumbing routed under a post-tension slab.
With a GPR layout, we can plan trenching between cables. And when work needs to happen near a stem wall, cables can sometimes be temporarily de-tensioned, the work completed, and then re-tensioned properly—but only when done under the direction of a post-tension specialist.
Pricing impact (high-level)
Post-tension work adds steps, specialists, and risk-management—which is why it changes pricing.
Here are the typical adders in a scenario like this:
GPR slab scan: ~$900
Post-tension concrete demo: ~$2,250 per area
Schluter Kerdi shower system upgrade: ~$1,800
In a typical curbless shower conversion on a post-tension slab, that can add roughly $5,000 compared to a standard slab scenario.
While that increases upfront cost, it dramatically reduces risk—and helps prevent much bigger problems down the road.
Our process, in a nutshell
When a remodel involves a post-tension slab, the process should look like this:
Scan the slab to confirm cable location and depth
Verify proximity to exterior walls/stem walls
Perform controlled demolition
Proceed with plumbing and construction safely
Thinking about a remodel on a post-tension slab?
If you’re planning a bathroom or kitchen remodel and your home sits on a post-tension slab, it’s worth working with a contractor who understands how to approach it correctly. If you’d like, I’m happy to talk through your project and help you understand what’s involved.