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Pad level

Pad level is the Reduced Level of the earthworks pad after cut, fill, and compaction, before footings. Typical tolerance ±25 mm. Confirmed by the surveyor.

By Chalkline. Last updated 14 May 2026. Verified 14 May 2026.

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Pad level is the Reduced Level (RL) of the prepared earthworks pad at the point earthworks finish and footings are about to start. It is the level the building sits on: footings excavate from it, slab edge beams form at it, and every height in the structure above it is measured from it.

Where the pad level sits in the build sequence:

  1. Design pad RL is shown on the engineer’s footing or slab design drawing, calculated to put the finished floor level at the design height, accounting for the slab thickness, screed (if used), and floor finish stack-up.
  2. Earthworks cut and fill bring the natural surface to within ±25 mm of design pad RL.
  3. Subgrade compaction and proof-roll lock the pad in.
  4. Surveyor confirms pad level by recording RLs at a grid of points (typically 5 to 10 across the pad) against the TBM.
  5. Footings excavate from pad level into the subgrade beneath.
  6. Slab pour sets the slab top at the design RL.

Tolerance. The typical industry tolerance is ±25 mm of design pad RL across the pad before the geotech accepts the works. Tighter tolerances (±10 to ±15 mm) are sometimes specified for waffle pod slabs or for designs with precise step-down requirements (e.g. wet area drop, garage slab step).

Why the tolerance matters.

  • Over-cut (pad below design RL): more concrete in the slab edge beams and waffle pods, or additional clean fill needed to bring back up. Cost and time.
  • Under-cut (pad above design RL): slab sits high, FFL goes wrong, the architectural step-downs in the design no longer work. Far more expensive to fix than over-cut.
  • Lumpy pad (within tolerance on average but ±50 mm point-to-point): difficult to form slab edge beams cleanly. Concretor needs to chase the high spots and pack the low spots.

Documentation. The surveyor’s pad-level confirmation is part of the geotech’s AS 3798 compliance report. The certifier wants to see the surveyor’s report at the slab pre-pour inspection.

For builders.

  1. Don’t skip the pad-level survey. It’s typically 1 to 2 hours and a few hundred dollars; it’s the cheap insurance against discovering the wrong pad RL after the slab is poured.
  2. Tie pad level to a permanent benchmark, not a temporary peg that might move during the excavation work. The TBM RL noted at site set-out is the reference.
  3. Communicate FFL clearly to the concretor. Pad level + slab thickness + floor finish = FFL. Mistakes here cascade up the entire build.

Also known as: design pad RL, platform level, pad RL.

Category: Surveying / earthworks / heights.

See also

Last updated: 2026-05-14. Verified: 2026-05-14.

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