Certificate III in Roof Tiling cheat sheet

Safe work at height: for roof work, use a fall-arrest system or guardrail when there is a risk of falling 2 m or more; a 1.8 m lanyard must not allow a free fall that puts the worker below the platform edge.

Roof pitch is expressed as a ratio of rise to run (e.g. 1:4 = 14°); pitch determines the minimum lap of sarking and tiles, so verify pitch before selecting materials.

Sarking lap rule of thumb: side laps not less than 150 mm and end laps not less than 150 mm, with laps running down-slope so water sheds over the lower sheet.

Tile batten spacing is set by the tile manufacturer's gauge; the gauge equals the tile length minus the head lap, and battens must be fixed to each rafter with the specified nail or screw.

Load limits: tiled roofs commonly impose 40–60 kg/m² dead load; confirm truss/rafter capacity and keep point loads (stacks of tiles) spread over several rafters.

Bedding and pointing mortar for ridge caps is typically a 3:1 sand:cement mix; flexible pointing compounds are used where movement is expected.

Flashings: valley, apron, and step flashings must be lapped so the upper element overlaps the lower, with a minimum 150 mm cover and no upward-facing open laps.

Hazard controls: asbestos-containing sheeting may be present on re-roofs; stop work and arrange identification/testing before disturbing any suspect sheeting.

Quality check: after laying, verify straight ridge lines, even tile courses, correct overhang at eaves (usually 40–50 mm past the fascia), and clear, unobstructed valleys.

Terracotta and concrete tiles differ in porosity and weight; terracotta is typically heavier per m², so batten and rafter capacity must be rechecked when substituting tile types.

Metal roofing electives: minimum roof slope for corrugated steel is commonly 5° for sheets with end laps, and lower (about 3°) for continuous long-length sheets with no end laps.

Wall cladding electives require cavity construction: a drained and ventilated cavity of at least 20 mm behind the cladding, with weep holes and flashings at the base.

Waterproofing electives: a shower recess membrane must extend at least 150 mm above the floor and 25 mm above the hob, with the floor graded 1:80 to 1:100 to the waste.

Estimating: tile quantity = roof area ÷ (tile coverage per m²) × (1 + wastage); allow 5–10% wastage for hips, valleys, and cuts.

Scaffolding electives: a working platform must be at least 450 mm wide, and guardrails top rail 900–1100 mm with a mid-rail and toe board.

Solar/roof penetration electives: every penetration needs a dektite or collar flashing matched to the pipe diameter and roof pitch, sealed to the tile profile.

Restoration electives: repointing is required where mortar has eroded more than about 10 mm; re-bed only after removing loose mortar and wetting the substrate.