Post-Tensioned Slabs and Penetrations: A Safe, Controlled Method

Penetrations through slabs require careful planning where post-tensioning may be present. Tendons and ducts are high consequence elements and accidental damage can create immediate safety risks and costly remedial works.

A controlled approach typically includes:

• Treating tendon presence as a credible risk until proven otherwise

• Establishing permitted zones based on scanning and structural review

• Using a permit-to-drill process with defined responsibilities and sign-off

• Planning sequencing so scanning, marking, and breakout are coordinated and verified on site

• Recording as-built outcomes for future maintenance and alterations

Even where scanning suggests clear zones, safe practice includes conservative assumptions, clear marking, and stop-work triggers if unexpected reinforcement or ducts are encountered. The objective is to achieve the required services and drainage outcomes without compromising structural performance or durability.