Find the term you're looking for.
NZ building reports use a mix of trade terminology, brand names that became generic, and old English roofing terms that haven't changed in a hundred years. None of them are explained, and none of them are written for the homeowner reading the report. This page does that.
Each entry is a short, clear definition, often with a note on what it looks like or where it sits on the roof. Where there's a related guide on the site, we link to it. Use the letter nav below to jump to a term, or scroll through the lot.
Reading your building report? If a building inspector has flagged something on the roof and recommended you engage a roofer, that's exactly what we do. See our guide on what to do when your building report flags the roof.
A
A flashing that runs along the bottom edge of a vertical surface (like a wall or chimney) where it meets a roof slope, directing water away from the joint and into the roof drainage. Common locations: bottom of chimneys, where a single-storey roof meets a two-storey wall, and at the base of dormer walls.
B
The board running along the gable end of a roof, covering the ends of the rafters or purlins. Often painted or stained to match the house exterior. Building reports often note "barge board deterioration" when paint is peeling or the timber is showing decay.
Horizontal timber strips fixed to the rafters that the roof tiles or metal sheeting are attached to. Battens carry the weight of the roof covering and transfer it to the rafters. On a tile roof you can see the tiles, but the battens are underneath holding them.
A gutter built into the roof structure (rather than hung off the edge), usually rectangular in cross-section. Common on commercial and apartment buildings, and on some character homes. If a box gutter fails it leaks into the building (not over the side) which is why building reports flag them.
A flexible black rubber-based membrane (proper name "polyisobutylene" but no one calls it that) commonly used on low-slope and flat roofs in NZ since the 1970s. See our Butynol vs TPO vs WeldTech guide for how it compares to newer membrane systems.
C
The way water moves through narrow gaps against gravity. Important in roofing because water can be drawn up under laps, into joints, and around flashings even when there's no rain falling. Good roof detailing breaks capillary paths.
The external covering of a building. "Roof cladding" usually means the metal, tile, or membrane material covering the roof. "Wall cladding" is the equivalent for walls (weatherboard, plaster, brick veneer).
A brand of pre-painted long-run steel roofing sheet, dominant in modern NZ residential roofing. Often used generically (any pre-painted long-run metal roof). Available in coastal-rated grades for marine environments.
A roof tile made from concrete, the dominant roof tile type on NZ homes built from the 1930s to 1970s. Hard-wearing, heavy, and long-lived, but the bedding mortar that holds the ridges in place has a finite life and is often the first thing to need attention.
A second flashing that sits over the top of a primary flashing (often a soaker), tucked into a wall, chimney or chase, providing a layered water barrier. Often used on tile roofs where they meet a chimney or wall.
D
A lightweight pressed-metal tile coated in stone chips, very common on NZ homes from the 1970s to 1990s. Looks like tile from the street, behaves like metal up close. Common wear pattern: stone-chip loss on weather-facing slopes, edge corrosion at the laps.
A small structure with its own roof that projects out from the main roof, usually with a window. Adds usable space in an attic or upper storey. Lots of flashings around a dormer: apron at the base, soakers up the sides, head flashing at the top.
The vertical pipe that carries water from the gutter down to ground level (or into a stormwater drain). Building reports often flag blocked, leaking, or missing downpipes.
A metal strip along the lower edge of the roof that directs water away from the fascia and into the gutter, rather than letting it track back along the underside of the roof covering.
E
The part of the roof that overhangs the wall of the building. Eaves protect the walls from rain and shade windows from sun. The underside of the eaves (the bit you see from below) is the soffit.
A general term for the flashings along the perimeter edges of a roof: rakes, eaves, verges, parapets. Edge flashings take the brunt of wind, so they're often where issues first show up on Wellington roofs.
F
The board running along the lower edge of the roof, where the gutter is fixed. Usually painted timber, sometimes PVC or aluminium on newer builds. Fascia rot is a common building report finding, often caused by gutter overflow or blocked spouting.
A thin strip of metal (lead, zinc, aluminium, painted steel) or other material used to seal joints and direct water away from vulnerable points on a roof. Found everywhere two different surfaces meet: chimney bases, wall abutments, valleys, ridges, dormers, penetrations. Building reports flag flashings more often than almost any other roof detail. See our guide on "deterioration noted to flashings" for what this usually means.
A flashing made from a flexible material (lead, malleable aluminium, or a butyl/PVC product) that can be shaped to fit over irregular surfaces like tiles. Common around chimneys on tile roofs.
G
The triangular section of wall at the end of a pitched roof, between the two slopes. A "gable end" is the wall under that triangle. Many older NZ homes are gabled at the ends.
A steel coating method (a layer of zinc applied to steel) that prevents rust. "Galvanised iron" or "galv" is the older name for what's now mostly replaced by Coloursteel and Zincalume. Original galvanised roofs can last 50+ years inland but corrode faster in coastal exposure.
The channel running along the lower edge of the roof that catches water and directs it to downpipes. NZ homes typically have hung half-round, PVC quad, or rectangular metal spouting. Blocked or sagging gutters are one of the most common building report findings.
H
A flashing at the top of an opening or surface (e.g. the top of a window, the top of a dormer wall meeting the main roof) that directs water away from the top edge.
The external angle where two sloping roof surfaces meet (going down from the ridge to the eaves). On a hipped roof, all four sides slope down to the eaves rather than ending in a gable. Hips have their own ridge tiles or capping along the line.
A tile (or metal capping) running along the hip line of a roof. Like ridge tiles, hip tiles are bedded in mortar on traditional tile roofs, and that mortar has a finite life.
I
See "box gutter". Any gutter built into the roof structure rather than hung off the edge. Important to flag because internal gutter failure leaks into the building.
L
Where one piece of roofing overlaps the next. Side laps run vertically up the roof; end laps run horizontally. Lap joints are designed to shed water in the direction the roof slopes. Issues at laps are common building report findings, especially on long-run metal that's getting on in years.
A flashing made from sheet lead, traditional on chimneys and other complex roof details. Lead is malleable, weather-resistant, and long-lived, but original lead flashings on NZ homes are often well past their useful life by now.
Roofing made from long continuous sheets of profiled metal (corrugated, tray, or similar), as opposed to short individual tiles. Dominant on modern NZ residential roofing. Usually Coloursteel or Zincalume.
M
A specific interlocking terracotta tile pattern, common on early 20th century NZ homes. If you see a tile with two distinctive ridge channels running down its face, that's often a Marseille pattern.
A general term for sheet waterproofing systems used on flat and low-slope roofs. Common types in NZ: butynol, TPO, WeldTech, EPDM. See our membrane comparison guide.
The cement-based mortar that holds ridge tiles, hip tiles and verge tiles in place on a tile roof. Has a finite life (usually 30-50 years) and is one of the most common maintenance items on older NZ tile roofs. "Loose pointing", "failed bedding" and "ridge mortar past its life" are all building report flags for the same thing.
P
A short wall extending above the roof level, usually around the edges of a flat or low-slope roof. Parapet flashings (where the parapet meets the roof membrane) are common leak points.
Anything that pokes through the roof: vents, flues, plumbing vents, antenna mounts, solar mounts, skylights. Each one needs a flashing around it where it meets the roof. Penetrations are common leak sources because the flashings around them have to work in three dimensions.
The angle of slope of the roof, usually expressed in degrees or as a ratio (e.g. 30 degrees, or "5 in 12" meaning 5 units rise over 12 units run). Steep pitches shed water faster but are harder to access safely. Flat or low-pitch roofs need membrane systems rather than tiles or long-run.
See "mortar bedding". The same mortar work, different name. Building reports use either term.
A horizontal structural timber that supports the roof, running between rafters or trusses. The roof battens (which the tiles or metal sheeting attach to) are usually fixed to the purlins. If a building report mentions "purlin issues", it usually means structural concerns inside the roof space.
R
A structural timber running from the ridge of the roof down to the eaves (or to a wall plate). The rafters carry the roof load. On older homes, rafters are usually individual timbers; on newer homes they're often part of prefabricated trusses.
The highest point of a roof, where two sloping surfaces meet at the top. The ridge runs along the length of the roof.
The capping that covers the ridge of a roof, sealing the joint between the two sloping surfaces. On a tile roof, ridge caps are individual tiles bedded in mortar. On a metal roof, the ridge cap is a long folded metal cap that runs the length of the ridge.
A flexible flashing material supplied in rolls, often a butyl or aluminium-and-bitumen composite, used to seal around irregular roof penetrations or as a soaker product.
S
Boards or sheeting fixed under the roof covering, between the rafters and the tiles or metal. Provides insulation, support, and weatherproofing. The word is also used loosely to refer to roof underlay (the building paper layer beneath the roof covering).
A roof made up of a series of identical pitched sections, each looking like a saw tooth from the side. Common on industrial and commercial buildings, occasionally seen on residential conversions.
A single-pitch roof (one slope only, no ridge). Common on mid-century modernist NZ homes and on contemporary architect-designed houses. Often low pitch, which means it usually needs a membrane rather than tiles.
A natural stone roofing tile, rare in NZ but found on a small number of heritage homes (and some imported European designs). Long-lived but fragile, and too brittle to take any foot load safely.
A small flashing piece fitted under each tile or shingle at an abutment (where the roof meets a wall, chimney or another roof section). Soakers work in combination with counter flashings or apron flashings to create a layered seal.
The underside of the eaves, visible when you stand under the overhang and look up. Soffit lining is usually painted timber, hardboard or fibre-cement. Damaged or rotten soffit linings are a common building report finding.
The NZ term for "gutter". The channel running along the lower edge of the roof that catches rainwater. See "gutter".
The closed end of a gutter or flashing, sealing off the open end so water doesn't spill out. Missing or failed stop ends cause water to leak at the wrong place.
T
A clay roof tile, fired to a reddish-brown colour. Common on NZ homes from around 1900 to 1940. Long-lived and weather-resistant but can crack under load, and the bedding mortar that holds ridges needs maintenance.
Thermoplastic polyolefin. A heat-welded membrane system used on low-slope roofs, increasingly common in NZ as a butynol alternative. See our membrane comparison guide.
A prefabricated triangular timber structure that supports the roof, replacing individual rafters on most homes built since the 1970s. If a building report mentions truss issues, it usually means structural concerns inside the roof space.
U
A waterproof layer between the roof structure and the roof covering, providing secondary weather protection if the primary covering leaks. Older homes used bitumen-impregnated paper; newer homes use synthetic membranes. Aged underlay is one of the most common things we point out on older Wellington roofs.
A vertical edge or kerb on a flat-roof membrane, where the membrane turns up against a wall, parapet or skylight. Upstands need to be high enough that water can't get behind them, and they have to be properly bonded or dressed at the top.
V
The internal angle where two sloping roof surfaces meet (the opposite of a hip). Valleys channel rainwater down the roof to the gutter. Often lined with a metal valley flashing, sometimes called valley iron.
The metal flashing lining a valley. Valleys carry a lot of water, especially on complex multi-pitch roofs, so valley flashings are common leak sources when they wear out or fill with debris.
A roof penetration used to vent air, gases, or moisture out of the building. Plumbing vents, bathroom extractor vents, range-hood discharges, gas flues. Each one needs a flashing where it passes through the roof.
The edge of the roof along a gable end (as opposed to the eaves, which run along the lower edge). On a tile roof, verge tiles or verge flashings finish the edge cleanly.
W
A heat-welded PVC membrane system commonly used on low-slope NZ roofs, particularly on commercial and apartment buildings. See our membrane comparison guide.
Z
An aluminium-zinc coated steel sheet, similar to galvanised but with better corrosion resistance. Often used as the unpainted alternative to Coloursteel.
This glossary is general educational content for NZ homeowners. It's not a building report, an engineering opinion, or a substitute for a roofing-focused inspection of your property. Definitions are simplified for plain-language use and may not capture every technical nuance. For specific roof concerns, get in touch for a roofing-focused assessment.