Building: Two storey mixed use alteration and addition: Class 5, Class 9b and Class 2, Type B construction
Location: Gippsland, Victoria
NCC edition: NCC 2022, Volume One
Area of NCC requirements: F3P1 weatherproofing; F3D5 wall cladding (and F3D2, F3D4 at openings and junctions)
Raised by: The relevant building surveyor
Year: 2026
The challenge
The new external walls are tilt up concrete panels. F3D5 only gives Deemed to Satisfy pathways for masonry to AS 3700, autoclaved aerated concrete to AS 5146.3 and metal cladding to AS 1562.1. Tilt up panels are not on that list, so even a well designed concrete wall needs a performance solution to show it meets F3P1.
The performance solution
Expert judgement, comparison with the Deemed to Satisfy Provisions and evidence of suitability, following the National Precast guidance note on weatherproofing precast concrete to NCC 2022. The F3V1 risk score method was not used because the walls are solid reinforced concrete. The report addressed the three ways water gets through a concrete panel wall:
Cracking. Panels designed by a structural engineer to AS 3600, including lifting and bracing stages, with crack control, cover to the nominated exposure classification, proper curing, and lifting and bracing inserts grouted flush.
Joints. Sealed and drained joints to National Precast details, with backing rod and a movement capable sealant, joint widths controlled within AS 3600 tolerances, and panel bases bedded and sealed to the slab.
Permeability. Concrete of at least 40 MPa at 28 days, properly compacted and cured, with no reliance on paint or coatings.
Windows and doors comply with AS 2047 and drain to the outside, with flashings, end dams and sealed perimeters, and penetrations are sleeved and sealed. Compared with the masonry that F3D5 accepts, a tilt up wall has no absorbent units and far fewer joints, each sealed and drained, so it performs at least as well.
Conditions
Joint types, sealant, flashings and window details shown on the drawings before the permit is issued, a structural engineer's certificate to the building surveyor, experienced tilt up and sealant contractors, inspection of each element before it is covered, and resealing joints at the sealant maker's recommended interval.
Outcome
Final report issued in September 2026 and successfully accepted by the relevant building surveyor.
Lesson for designers
If a wall system is not named in F3D5, plan for a performance solution early. For concrete, the answer is usually in the joint and opening details, so get them on the drawings before the permit stage.
Related: Performance solution report | Performance Solution vs Deemed to Satisfy
Need a performance solution for a similar problem? Request a fee proposal or phone 0407 560 708.