Study notes — CPCCCA3007 Construct pitched roofs

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What this unit is about

This unit covers setting out, cutting and erecting the timber members of a pitched roof — from marking the top plates and developing a pattern rafter, through hips, valleys and creepers, to under-purlins, struts, collar ties and tie-downs — and finishing with a clean, safe site. It matters because a pitched roof is built from geometry, not guesswork: get the bevels, lengths and supports right to AS 1684 and the National Construction Code, and the whole roof goes up straight, strong and safe.

What you must be able to show

Set out, construct and erect a skillion roof above 10° over at least 10 m².
Set out, construct and erect a roof (or roofs) covering at least 30 m² that includes a broken hip and valley, a gable end and a scotch valley.
Set out a pattern rafter with birdsmouth, creeper reductions and eave overhang, plus all roof bevels.
Set out strutting beams and under-purlins to the span tables in AS 1684 and manufacturers’ specifications.

Element 1

Plan and prepare

Read the paperwork first. Work through the drawings, specification and work instructions; identify the roof type, pitch, spans and rafter spacing, then plan the sequence of work before you pick up a saw.
Plan for compliance. Every step must satisfy WHS and environmental laws, the National Construction Code (NCC), Australian Standards — especially AS 1684 Residential timber-framed construction — manufacturers’ specifications, and your workplace’s own procedures.
Tools and equipment. Select what the job needs, check each item is serviceable, and tag out and report anything faulty. A damaged lead or a saw with a sticking guard never goes to work.
PPE for each part of the task. Select and wear what the current task calls for — eye and hearing protection when cutting, gloves for handling, and change as the task changes.
Inspect the site before starting. Locate services (overhead power especially), assess hazards and put risk controls in place, including signage and barricades. Roof framing is work at height — falls controls and a SWMS come before any work starts, and it belongs in the toolbox talk.
Materials. Work out types and quantities from the plans, order and check them, then handle, stack and position them safely, ready for use.

Element 2

Set out, prepare and erect pitched roof members

Set out the top plates. Mark the position of every member on the plates to suit the roof type and the specified rafter spacing — everything is located before anything is cut.
Determine the bevels for all members. Plumb and level cuts for commons; their own flatter plumb and level cuts plus edge bevels for hips and valleys; edge bevels for creepers and face/edge bevels for purlins. All of them come from the roof’s geometry (its rise per metre of run), developed with a steel square, roofing calculations or a full-size set-out.
Develop a pattern rafter. Calculate its true length, mark the birdsmouth over the plate, add the eave overhang and mark the creeper reductions. Every common and creeper is cut from this one template.
Ridge boards. Set out and cut the main ridge boards to length and transfer the rafter positions onto them from the plates.
Cut the commons — and check. Cut common rafters from the pattern and try the first pair in position before cutting the rest of the stack.
Erect in the correct sequence. Opposing pairs at each end of the ridge first, ridge sighted straight and braced, then the pairs in between filled in.
Hips and valleys. Calculate their lengths from the roof pitch — their run is the diagonal in plan, so they’re longer and flatter than commons. Cut and fix them with their own bevels.
Creepers. Cut them from the pattern rafter with an equal reduction per spacing, keep the overhang line true, and fix them in opposing pairs so the hip isn’t pushed out of line.

The pattern rafter: true length runs from the ridge to the birdsmouth; the eave overhang is added beyond the plate. Rise over run sets the pitch — and the pitch sets every bevel on the roof.

Member	Bevels / cuts needed	Why
Common rafter	Plumb cut · level (foot) cut	Plumb against the ridge, seat on the plate. The creeper borrows the same plumb cut.
Hip / valley rafter	Hip plumb · hip level · edge bevel	Its run is the plan diagonal, so its bevels are flatter than the commons’.
Creeper rafter	Common plumb + creeper edge bevel	The edge bevel lets the shortened rafter sit flush against the hip or valley.
Under-purlin	Face and edge bevels	So it beds tight under the sloping rafters at splices and hip ends.

Plan view of a broken hip and valley roof with a gable-ended wing — step through the erection sequence.

Element 3

Install roof support

Under-purlins. Determine their lengths, then cut and fix them under the rafters at mid-span (or as the span tables require) to reduce the rafters’ effective span.
Struts. Measure, cut and fit struts from the under-purlins, hips, valleys and ridge down to load-bearing walls or strutting beams — solid bearing, within the angle limits, never off ceiling joists mid-span.
Collar ties and tie-downs. Install them to the span tables in AS 1684. Tie-downs resist wind uplift and are non-negotiable — check the required fixing type for your wind classification.
Gable ends. Fit trimmers to carry the gable-end rafter and the barge board at the verge.
Valley boards and battens. Cut and fix valley boards and the surrounding battens so the valley gutter and roof covering have continuous solid support.

Element 4

Clean up

Clean as you go and at the end. Sort waste, recycle offcuts where you can, and dispose of the rest to meet legislative and workplace requirements — nothing left on the frame or dropped over the edge.
Handle leftover materials safely and stack reusable stock properly for the next stage or job.
Tools and equipment. Check, maintain and store everything; report (and tag out) any faults so the next person isn’t handed a hazard.

Knowledge evidence

Know this cold

NCC and AS 1684. Where roof compliance comes from: member spans and spacings, stress grades, strutting rules, and tie-down/fixing requirements. Manufacturers’ span tables govern engineered products.
Workplace quality standards. Tolerances for straight, level and plumb; checking as you go, not at the end.
Safety requirements. Falls from height (SWMS for high-risk construction work), edge protection and scaffold, ladder use, manual handling of long stock, power tool and lead safety, and stopping work in unsafe weather.
Framing techniques and sequence. How a pitched roof goes together and the order that keeps it straight and safe while it’s still flexible.
Plans, specifications and symbols. Pitch notation, spans, section marks, scales and abbreviations used on roof drawings.
Tools and equipment. Steel/roofing square, circular saw, nail guns, levels, string lines, saw stools, ladders and access equipment — what each is for and how to check it.
Set-out and calculation processes. True length per metre of run, rafter counts from spacing, and material quantity take-offs.
Materials. Seasoned and unseasoned timber, MGP stress grades, engineered products such as LVL, and steel connectors (triple grips, framing anchors, straps, bolts) — their structural properties and correct uses.
Set-out procedures. Pattern rafter development, plate and ridge set-out, centring (crown-end) rafters at hip ends.
Roof types and their character:
- Gable and verge — two faces meeting at a ridge, ending at vertical gable walls; the verge overhang is trimmed with a barge board.
- Hip and valley — hips slope back from external corners; valleys form at internal corners where two surfaces meet.
- Broken hip and valley — a wing meets the main roof so a shortened (broken) hip and a valley spring from the same point.
- Scotch valley — the wing roof is built over the main roof’s continuous rafters on a valley board; no cut valley rafter.
- Skillion — a single sloping surface with no ridge.
- Strutted roofs — rafters supported mid-span by under-purlins, struts and props to walls below.
Geometric development of bevels. How every bevel on the roof — common plumb and level, hip plumb, level and edge, creeper edge, purlin face and edge — is developed from one geometric set-out of rise and run.

Watch out

Where people slip up

✗ Forgetting the ridge deduction. The true length runs to the roof’s centreline, so rafters cut to it finish long and the ridge crowns or bows.

✓ Fix: deduct half the ridge thickness, measured square (at right angles) to the plumb cut, before cutting.

✗ Cutting the birdsmouth too deep. A deep notch looks like better seating but it guts the rafter right where the overhang cantilevers.

✓ Fix: keep the birdsmouth to a maximum of one-third of the rafter depth.

✗ Cutting the whole stack from an unchecked pattern. One error in the template multiplies into a pack of expensive firewood.

✓ Fix: try the pattern (or the first pair) in position and check the fit at ridge and plate before cutting the rest.

✗ Muddling the creeper reduction. Measuring the shortening along the plate, or skipping the edge bevel, leaves creepers that won’t sit on the hip.

✓ Fix: the reduction per spacing is constant and is set out along the rafter, square to the plumb line — and every creeper still gets its edge bevel.

✗ Landing struts anywhere handy. A strut onto a ceiling joist mid-span just transfers the roof load to a member that can’t take it.

✓ Fix: struts bear only on load-bearing walls or strutting beams, within the angle limits in AS 1684.

Reference

Mini-glossary

Pitch: The slope of the roof, given in degrees or as rise per unit of run.
Span, run and rise: Span is the width over the wall plates; run is half the span (for a common rafter); rise is the vertical height gained over that run.
Top plate: The horizontal member on top of the wall frame that the rafters bear on — where the roof is set out.
Ridge board: The horizontal board at the apex that the rafter plumb cuts bear against.
Common rafter: A full-length rafter running from top plate to ridge.
Pattern rafter: The first, carefully set-out rafter used as the template for cutting all commons and creepers.
Birdsmouth: The notch (horizontal seat cut plus vertical plumb cut) that seats the rafter on the top plate — maximum one-third of rafter depth.
Plumb and level cuts: The vertical (plumb) and horizontal (level) cuts on a rafter, set from the roof’s bevels.
Eave overhang: The part of the rafter projecting past the wall to form the eave.
Hip rafter: The rafter running from an external corner up to the ridge, on the plan diagonal.
Valley rafter: The rafter at an internal corner where two roof surfaces meet, collecting the valley creepers.
Creeper rafter: A shortened rafter running from plate to hip (or valley to ridge), each one reduced by the same amount per spacing.
Crown-end (centring) rafter: The common rafter at the centre of a hip end, running square from the end plate to the end of the ridge.
Under-purlin: A member fixed under the rafters mid-span to reduce their effective span, supported by struts.
Strut and strutting beam: A strut props under-purlins, hips, valleys or ridge down to a load-bearing wall; a strutting beam carries struts where no wall is available.
Collar tie: A horizontal member connecting opposing rafters to resist spread, installed to AS 1684.
Tie-down: The strap, bolt or framing anchor that holds the roof frame down against wind uplift.
Gable, verge and barge board: The gable is the triangular end wall; the verge is the roof edge above it; the barge board trims and finishes the verge.
Scotch valley: A valley construction where the wing roof is framed over the main roof’s continuous rafters on a valley board.
Skillion: A roof with a single sloping surface and no ridge.
Trimmer: A short member fitted at a gable end to carry the gable-end rafter and barge board.
Valley board: The wide board fixed in the valley that supports the valley gutter and surrounding battens.

Finish

You’ve reached the end

That’s the whole unit in one pass: plan and prepare, set out and erect the members, install the support system, and clean up properly. Print these notes as a handout, or come back before your practical check.

Or just scroll through every section — your progress is tracked in the list above.