Scanning before you drill
The expensive mistakes are all invisible from the surface.
What you are looking for
- Reinforcement, which is a structural and practical problem.
- Post-tensioning tendons, which are a catastrophic problem — cutting one can be life-threatening and can compromise the structure.
- Electrical, data, gas and water services buried in or behind the element.
Tools
Cover meters and rebar locators for reinforcement; ground-penetrating radar for deeper or more complex scanning; cable detectors for services.
Each has limitations. Depth, congestion and moisture all affect reliability.
Post-tensioned slabs
Treat any suspected post-tensioned element as drill-free until proven otherwise by competent survey and the structural engineer's approval. This is not a judgement call for the operative.
Related
See what to do when you hit rebar.
Questions about this
What is the most serious thing to hit?
A post-tensioning tendon. Cutting one can be life-threatening and can compromise the structure. Treat any suspected post-tensioned element as drill-free until cleared by competent survey.
Is scanning always reliable?
No. Depth, congestion and moisture all affect results, and different technologies have different limitations. Scanning reduces risk; it does not eliminate it.