Steel Sections & Reo for NZ Builds

A plain-English rundown of the structural steel sections and reinforcing you order on NZ residential jobs – what the designations mean, where each shape earns its keep, and the current reo rules.

Quote a job free Browse the code guide

Steel earns its place in a house where timber runs out of puff – long clear spans, big point loads (a beam carrying a wall over a wide opening), or slim posts. Get the designations and the reo grades straight and you order the right member the first time.

How to read a steel designation

The designation reads as shape + nominal mass per metre. A 200UB22 is a 200 mm-deep Universal Beam weighing 22 kg/m. The shape codes tell you what you’re looking at:

UB – beam
UC – column
PFC – channel
RHS / SHS / CHS – hollow sections

All of these are made to AS/NZS standards.

Hot-rolled sections

Universal Columns & Beams (UC / UB)

Used for portal frames, transfer beams and heavy lintels, designed to NZS 3404. Typical sizes run UC 100UC15, 150UC23, 200UC46, 250UC73, 310UC97; and UB 150UB14, 180UB18, 200UB22–30, 250UB31–37, 310UB32–46.

Parallel Flange Channel (PFC)

Common for lintels and beams in residential – often a single PFC over a wide opening. Sizes run 100PFC, 125PFC, 150PFC, 180PFC, 200PFC, 230PFC, 250PFC, 300PFC.

Hollow sections (RHS / SHS / CHS)

RHS (Rectangular) – posts, frames, pergolas, sub-floor beams; often hot-dip galv for exterior. Sizes 50×25 up to 300×200, walls 2.0–12 mm.
SHS (Square) – architectural posts, portals, light structural. Sizes 25×25 up to 250×250, walls 2.0–12 mm.
CHS (Circular) – round posts, columns, archy steel. Sizes 32–273 mm OD, walls 2.6–25 mm.

Cold-formed & light steel

Purlin sections (Z + C)

Cold-rolled roof and wall purlins to AS/NZS 4600 – lighter than rolled section. Sizes Z150, Z200, Z250, C100, C150, C200.

Steel framing (Howick, NASH)

Light gauge steel framing for residential, an alternative to timber – lighter, dimensionally stable, no shrinkage, and available as CodeMark-certified systems. A typical stud is 92×35×0.75 mm.

Reinforcing (reo)

Reinforcing bar

Used for structural concrete reinforcing. Sizes run D10, D12, D16, D20, D25, D32 in Grade 500E ductile seismic (AS/NZS 4671:2019).

Reinforcing mesh

For slab reinforcement. SE62 is the minimum for a residential slab per NZS 3604 + BRANZ:

SE62 – 2.27 kg/m², 6.0 mm @ 200 mm grid
SE82 – 4.04 kg/m², 8.0 mm @ 200 mm
665 yard mesh – NON-STRUCTURAL only (driveways)

Grade 500E – the current requirement

All structural concrete reinforcing in NZ residential MUST be Grade 500E ductile seismic (AS/NZS 4671:2019). Older 300E/300 grade is no longer compliant for new work.

Check the rebar tag at delivery – 500E will be marked.

Corrosion protection

Match the coating to the exposure zone:

Hot-dip galvanised – standard exterior. Coating ~50µm. Lasts 30–50yr Zone B, 15–25yr Zone D.
Duplex coating – HDG + paint topcoat. 60–80yr Zone D.
Powder coat over HDG – architectural, durable, expensive.
Stainless steel 316 – coastal, marine. Highest cost.

Plain-English guide, not advice. This page helps you understand and navigate the rules — it is general information, not design, engineering or consent advice, and it does not reproduce the copyrighted tables of NZS 3604 or any Standard. Always check the current Standard or Acceptable Solution and your BCA, and use a suitably qualified LBP, engineer or QS where it matters.

Do it in Toolie

Put this into practice with the material calculators · quoting with an NZ pricebook. Try Toolie free — no signup — or open this topic in the Toolie app.

Common questions

What does a designation like 200UB22 actually mean?

It reads as shape + nominal mass per metre. A 200UB22 is a 200 mm-deep Universal Beam weighing 22 kg/m. The letters are the shape code: UB is a beam, UC a column, PFC a channel, and RHS/SHS/CHS are hollow sections – all made to AS/NZS standards.

What grade of reo is required for NZ residential concrete?

All structural concrete reinforcing in NZ residential MUST be Grade 500E ductile seismic (AS/NZS 4671:2019). Older 300E/300 grade is no longer compliant for new work. Check the rebar tag at delivery – 500E will be marked.

What mesh do I use in a residential slab?

SE62 is the minimum for a residential slab per NZS 3604 + BRANZ (2.27 kg/m², 6.0 mm bar at a 200 mm grid). SE82 is heavier (4.04 kg/m², 8.0 mm at 200 mm). 665 yard mesh is non-structural only – driveways.

Which corrosion protection suits a coastal job?

For coastal or marine exposure, stainless steel 316 is the top option (and highest cost). Otherwise hot-dip galvanised is standard exterior (~50µm, lasting 30–50yr in Zone B and 15–25yr in Zone D), and a duplex coating (HDG plus paint topcoat) lifts that to 60–80yr in Zone D.

More in Materials

All Materials topics → · Full NZ Building Code index

Quote it, comply, get paid — in one app

Toolie turns this knowledge into the job: NZS 3604 take-off, H1 & Healthy Homes, consents, retentions and invoicing — one flat NZD price.

Quote a job free →