Core Drilling a Post-Tension Slab in Dubai

Many Dubai towers and podiums are post-tensioned. The tendons are stressed steel, and the slab was calculated with those forces in place. A core drill that cuts one is not a patching job. It is a structural incident. The drill is still the right tool for a sleeve. It has to land between the cables, on a point someone has accepted.

Find out if the slab is post-tensioned before you set out

Ask the structural drawings, not the site rumour. Look for tendon profiles, live-end and dead-end pockets, and notes that say PT or post-tension. If the drawing is missing, assume you need a scan rather than assuming mild steel. Transfer slabs, long spans and thin flat slabs in towers are the usual places this question matters.

Scanning before drilling is how those cables get marked on the concrete. Concrete scanning and the drill should be booked as one sequence.

Agree the centre, then drill

MEP set-out often puts a pipe on the shortest route. That route may cross a tendon band. The conversation with the engineer is: move the sleeve, or prove this point is clear. Once the mark is accepted, the core drill stays on that mark. A driller should be allowed to stop if the cuttings or the scan do not match what was agreed.

Do not ask the crew to “go carefully” through an unmarked slab. Careful is not a method.

What the brief should contain

• Structural drawing reference, or a clear statement that no drawing exists
• Hole diameter, depth and whether it is a through-hole
• Who will approve a moved centre on the day
• Protection below, because a core can drop
• Whether the report must go back to the consultant before drilling

If approval has to leave site, do not book the drill for the same hour as the scan. You will pay for standing time or you will be pressured to drill early.

After the hole

Photograph the core and the finished hole against the mark. If the sleeve shifts later, the next trade needs to know the slab was drilled where the engineer said, not where the first drawing showed. Fire stopping and the sleeve itself are usually builder’s work unless the quote says otherwise.

Typical diameters for those sleeves are listed in the MEP hole-size guide. Send the PT note with the hole list when you request a quote.

Common questions

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