Study Notes — CPCCCA3016 Timber External Stairs

☰What this unit is about

This unit covers building a flight of external timber stairs from the ground up — reading the plans, calculating rise and going, setting out and housing the stringers, fixing treads, fitting handrails and balustrade, and leaving the site clean. Stairs are one of the most unforgiving jobs in carpentry: get the numbers right and people walk safely between levels for decades; get one riser wrong and you've built a trip hazard that fails inspection and has to come out.

What you'll be assessed on: constructing, assembling and installing one flight of timber external stairs from ground level to a height of at least 1.1 metres, including a handrail and balustrade to the open side of the flight and the landing.

Anatomy of a timber external stair — side view.

1Plan and prepare

Read the paperwork first. Work through the drawings, specifications and work instructions, then plan the sequence of work before touching a tool — stairs are set out on paper before they're set out on timber.
Plan to comply. Every decision has to line up with the National Construction Code (NCC), the relevant Australian Standards, WHS and environmental requirements, manufacturers' specifications and your workplace's own procedures — not just "how we've always done it".
Check your tools. Select the tools and equipment the job needs, inspect them for serviceability (guards, leads, tags, sharp blades), and report and tag out anything faulty — never quietly put a dud tool back on the truck.
PPE per task, not per day. Match protection to each part of the job: eye and hearing protection when cutting, gloves when handling treated timber, dust protection when sawing or sanding treated pine.
Inspect the site before you start. Locate underground and overhead services, identify hazards (uneven ground, other trades, weather, manual handling), apply risk controls, and put up the required signage and barricades. This is SWMS and toolbox-talk territory.
Materials sorted before the first cut. Select the right materials, calculate quantities from the drawings, handle them safely (team lifts for long stringers), and stack and position them ready for use so you're not double-handling.

2Set out stair components

Find your two levels. Determine the exit (top) level and the finished ground level from the site drawings and the actual site — the vertical distance between them is your total rise, and everything else flows from it.
Calculate rise and going. Divide total rise by a trial riser height to get the number of risers, then adjust so every riser is identical and the rise, going and slope relationship all sit inside NCC limits (see "Know this cold" below).
Set out the newel posts to the designed stair layout — their positions fix the width, the start and finish of the flight, and where the balustrade lands.
Mark the stringers. Set out risers and goings on the stringers with a steel square and stair buttons (fence) so the flight sits at the regulated pitch — consistent, accurate, and checked before cutting.
Prepare the tread supports. Either house (trench) the stringers to receive the treads, or fix metal brackets to the stringers to carry them — both are accepted methods; the drawings tell you which.
Cut treads to length from your set-out, allowing for housings or brackets and any nosing overhang, so the flight finishes at the specified width.

The golden rule of set-out: every riser in the flight must be the same height. A person's feet learn the rhythm of a stair within two steps — one odd riser is the classic trip point.

3Assemble and install the stairs

Cut and fix the stringers, attaching them into the newel posts at the bottom and to the landing or deck structure at the top — this connection carries the whole flight, so fixings must suit external use.
Fix the treads to the stringers — glued and screwed into housings, or screwed/bolted to brackets — checking each tread for level across its width and line along the flight as you go.
Fit stair bolts (tie bolts) across the flight to lock the stringers at the correct width so the stair can't spread under load over time.
Brace it. Fix bracing and lateral ties to the newels so the whole structure is rigid — an external stair gets sideways load every time someone grabs the rail, and it must not rack or wobble.
Keep checking line, level and plumb through the whole assembly: treads level, newels plumb, stringers in line at the designed pitch. Small errors compound fast on a flight.

4Fit handrails, balustrade and finish

Mark and cut handrail and baluster material to length from the installed flight — measure the actual stair, not just the drawing, because the built pitch governs the rail angle.
Fit and fix the handrail and balusters to the open side of the flight and the landing: rail at compliant height above the tread nosings, balusters spaced so no opening lets a 125 mm sphere pass through, all fixings suited to external exposure.
The rail must be graspable and solid — it has to take a real load from a person catching themselves, not just look the part.
Install a non-slip finish to the treads — grooved/profiled treads, adhesive strips or applied nosing products — because a wet timber tread is genuinely dangerous. External stairs must have slip-resistant surfaces.

5Clean up

Clean up to the rules, not just to look tidy: meet legislative and workplace requirements for safety, waste disposal, materials handling and protection of the environment.
Treated timber offcuts are controlled waste — never burn them and never leave them where they can enter soil or waterways; dispose of them as your site and local requirements direct.
Sort and recycle what can be reused or recycled; separate general waste from timber and metal.
Tools last if you look after them: check, clean, maintain and store tools and equipment properly, and report any faults so the next user doesn't pick up a dangerous tool.

★Know this cold

Compliance — NCC and Australian Standards

External stairs on housing must comply with the NCC and referenced Australian Standards. The numbers below are the ones assessors and building surveyors check first:

Requirement	Rule of thumb (Class 1 housing)
Riser height (R)	115 mm – 190 mm, and equal throughout the flight
Going (G)	240 mm – 355 mm, equal throughout the flight
Slope relationship	2R + G between 550 mm and 700 mm
Handrail height	At least 865 mm above tread nosings; landings with a fall over 1 m need a 1 m barrier
Balustrade openings	No gap allowing a 125 mm sphere to pass
Tread surface	Slip-resistant surface or nosing strip on external stairs

Safety and quality

WHS requirements: SWMS where required, service location before excavation, signage and barricades, safe manual handling, PPE matched to each task, and your workplace's quality policies and standards for finished work.
Line, level and plumb: treads dead level, newels plumb both ways, stringers straight and in line at the designed pitch — checked constantly, not just at the end.

Materials and durability

External timber must be durable: naturally durable species (durability class rated for outside use) or preservative-treated timber — H3 treatment as the minimum for exposed above-ground work, higher for in-ground posts.
Fixings must match: hot-dip galvanised or stainless steel bolts, screws and brackets — bright steel rusts and stains, and some treatments corrode unprotected fixings.
Measure and calculate: total rise ÷ riser height = number of risers; number of treads = risers − 1 (the landing is the top "tread"); stringer length comes from the rise/going triangle (think Pythagoras).

Techniques, tools and types

Joining and fixing methods: housed (trenched) stringers with glued-and-wedged or screwed treads; cut stringers with treads fixed on top; metal brackets; stair bolts across the flight; bolted newel connections; bracing and lateral ties.
Tools: steel square and stair buttons, levels, string lines, circular saw, router or trenching for housings, drills, clamps, chisels, and the measuring and marking gear for set-out.
Stair types: straight flight, quarter-turn (L), half-turn/dog-leg (U), open riser vs closed riser, cut stringer vs closed (housed) stringer — know how each carries its treads.
Handrails and balusters: profiled vs pigtail-free graspable rails, timber vs metal balusters, top-fixed vs side-fixed — each has different fixing details but the same compliance numbers.

!Where people slip up

✕

Measuring total rise from the wrong points. Total rise is finished exit level to finished ground level — not deck frame to dirt.

✓ Establish both finished levels on site before any calculation, and re-check after the ground is prepared.

✕

Forgetting to "drop the stringer". If you don't reduce the bottom riser by the tread thickness, the first step ends up one tread too tall and the top one too short.

✓ Deduct one tread thickness from the bottom of the stringer so every finished riser measures the same.

✕

Interior-grade timber and bright steel fixings outside. They look fine on handover day and fail within a couple of seasons.

✓ Use durable or H3-treated timber and hot-dip galvanised or stainless fixings — always.

✕

Balustrade "near enough". A rail at 820 mm or a 140 mm baluster gap is a straight fail and a genuine fall risk for kids.

✓ 865 mm minimum above nosings on the flight, and no opening that passes a 125 mm sphere. Measure, don't eyeball.

✕

Digging post holes without locating services. Gas, water, power and comms run exactly where you'd rather they didn't.

✓ Locate services as part of the site inspection before any excavation — every time.

A–ZMini-glossary

Rise / riser: The vertical height of one step; the riser is the vertical face (or open gap) between treads.
Going: The horizontal depth of one step, measured nosing to nosing.
Total rise: The full vertical distance from finished ground level to the finished exit level.
Pitch: The slope of the flight, set by the relationship between rise and going (the 2R + G rule).
Stringer: The sloping board that carries the treads. A closed stringer is housed; a cut stringer is sawn to the step profile.
Housing: A trench routed into a stringer that a tread sits into.
Tread: The horizontal board you step on.
Nosing: The front edge of a tread, often overhanging the riser; where a non-slip strip goes.
Newel post: The main upright post at the start, end or turn of a flight that anchors the stringers and balustrade.
Baluster: One of the vertical infill members between rail and stair that stop falls through the side.
Balustrade: The whole barrier assembly — newels, handrail and balusters — on the open side of a flight or landing.
Stair (tie) bolt: A bolt fitted across the flight to hold the stringers at the correct width.
Line, level and plumb: Straight along its length, horizontal across, vertical up-and-down — the three checks that make a stair true.
H3 treatment: Preservative treatment level for timber exposed to the weather above ground.

Nice work — these notes are marked as read. Print them for revision if it helps.