Anchoring Pallet Rack Into Post-Tensioned Slabs in DFW
November 10, 2026
Before you drill anchor holes for pallet rack in a DFW warehouse, find out whether the slab is post-tensioned. A post-tensioned slab holds steel tendons under high tension, and drilling into one is dangerous and expensive to repair. Scan the slab with ground-penetrating radar, get the as-built drawings, and mark every tendon before anchoring.
Most warehouse slabs in North Texas are conventionally reinforced slab-on-grade, but post-tensioned slabs do exist in the region, and you cannot tell by looking at the floor. A rack crew that assumes "it's just concrete" is making a guess with a bad downside.
What is a post-tensioned slab, and why does it matter for rack anchors?
In a conventional slab, rebar or welded wire sits in the concrete and does its work passively. In a post-tensioned slab, steel cables (tendons) run inside plastic sheathing and are stretched after the concrete cures, then locked off. The slab stays in compression, which lets builders pour thinner slabs and control cracking over long spans.
That stored force is the problem. A masonry bit or core drill that cuts a tendon can release that tension suddenly. Depending on where the tendon is cut, the result ranges from a damaged slab to injury to the person drilling. Even a drilled hole that misses the tendon by a small margin can nick its sheathing and let moisture in over time.
How do I find out if my warehouse floor is post-tensioned?
Work through these in order. Each step is cheap compared to a repair:
| Step | Who to ask | What you are looking for |
|---|---|---|
| 1. Ask the landlord or property manager | Building owner | Whether the slab is post-tensioned, and who the original contractor was |
| 2. Request as-built drawings | Owner, GC, or city records | Tendon layout, spacing, and any "no-drill" notes |
| 3. Look for stressing pockets | Slab edge or perimeter | Small patched recesses at the edge that hint at tendon ends |
| 4. Commission a scan | GPR or X-ray scanning contractor | Actual tendon and rebar locations marked on the floor |
1. Ask the landlord or property manager
- Who to ask
- Building owner
- What you are looking for
- Whether the slab is post-tensioned, and who the original contractor was
2. Request as-built drawings
- Who to ask
- Owner, GC, or city records
- What you are looking for
- Tendon layout, spacing, and any "no-drill" notes
3. Look for stressing pockets
- Who to ask
- Slab edge or perimeter
- What you are looking for
- Small patched recesses at the edge that hint at tendon ends
4. Commission a scan
- Who to ask
- GPR or X-ray scanning contractor
- What you are looking for
- Actual tendon and rebar locations marked on the floor
Drawings can be incomplete or wrong, which is why the scan matters even when you have paperwork. If the building owner confirms there are tendons, treat the scan as mandatory rather than optional.
What does a scan change about the rack layout?
Rack base plates have fixed anchor hole patterns, usually two holes per plate. A scan produces marked "clear zones" on the slab. Your rack designer then checks whether each column location has a clear spot for its anchors.
When a column lands on a tendon, the options generally include:
- Shifting the layout slightly so base plates avoid the tendon line
- Using the slotted or alternate holes in the base plate, where the plate allows it
- Having an engineer specify a different anchor type or embedment depth for that location
- Replacing a conflicting bay with a different configuration
Those are decisions for the rack engineer and the slab's engineer of record, not for a crew improvising on site. Our guide to pallet rack anchors in Dallas covers standard anchor selection, and the base plate checklist explains what the plate itself has to provide.
Should the scan happen before or after the rack order?
Before is better, because the scan can change the layout. If the order is already placed, scan before the install date and give the results to whoever is anchoring. Stock rack from NAWL dispatches from Venus, TX within 48 hours on stock orders, so the scan is often the longest lead item on a fast project. Schedule it first.
Who is responsible if a tendon gets hit?
That depends on the lease, the install contract, and who directed the drilling. Settle it in writing before work starts. Ask your installer whether their scope includes slab scanning, and ask the landlord whether they require scanning or a permit for floor penetrations. Many commercial leases do.
Frequently asked questions
Does every Dallas-Fort Worth warehouse have a post-tensioned slab? No. Most industrial slabs here are conventionally reinforced. The point is that you cannot tell visually, so you verify instead of assuming.
Can I use adhesive anchors or shallower anchors to avoid tendons? Possibly, but anchor type and embedment are engineering decisions tied to the rack's load and the slab's thickness and strength. Do not substitute anchors on your own.
How accurate is a GPR scan? Scanning is widely used for this purpose and generally locates tendons and rebar well, but results depend on slab thickness, moisture, and operator skill. Choose a scanner with experience in post-tensioned slabs.
Does this apply to freestanding shelving? Light shelving that is not anchored does not drill into the slab. Anything anchored, including pallet rack and cantilever rack, does.
Planning an install on an unknown slab?
Send us your layout and we will help you line up the rack before the scan results come back.