Thinner slabs, longer spans and fewer columns: PT flat slabs can unlock extra storeys within the same building envelope. We break down the commercial case and the buildability trade-offs.
Thinner slabs, taller returns
The headline benefit of a post-tensioned flat slab is depth. Less structural zone per floor means either a lower overall building — cheaper cladding and cores — or, more often in a height-limited scheme, an additional lettable floor within the same envelope.
On a commercial scheme that extra floor is pure upside, and it is the single argument that most often tips a developer towards PT.
Fewer columns, more flexible space
Longer spans mean fewer columns, which means more flexible, more lettable, more re-configurable floorplates. For offices and build-to-rent that flexibility has a direct value, and it is hard to retrofit into an RC grid after the fact.
Material and carbon efficiency
PT uses concrete and reinforcement more efficiently, so per square metre it can carry less embodied carbon than an equivalent RC slab — particularly when paired with cement replacement. It is not automatic, but on the right spans it is a genuine lever.
The trade-offs to plan for
PT is not free of complexity. Penetrations and future alterations need care around tendon zones, stressing must be sequenced against early-age strength, and you need a contractor who does this routinely. Procured well, those are managed risks, not reasons to avoid PT.
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