A glossary for roof reports
Parts of a roof, in plain English.
The names of the parts of pitched, flat and metal roofs, from rafters to rooflights, with what to look for on each one in a survey. For surveyors, estates teams and building owners who write or read roof reports.
For roofs in the UK. Checked against the Planning Portal and HSE on 13 October 2026. Next review by 13 April 2027.
Why the names matter
One name for each part, used every time.
A roof report is read by people who were not on the roof: a client, a finance team, a roofer pricing the repair. If the report says "the edge" when it means the verge, the roofer may price the wrong job. Use the trade name for each part, the same way every time, and the report is easy to act on.
Roofs come in two broad kinds. A pitched roof slopes, and is usually covered in tiles or slates laid over a timber frame. A flat roof is close to level, with a continuous waterproof layer over a deck. Metal sheet roofs, common on industrial and commercial buildings, can be either.
The timber frame of a pitched roof does more than hold up the tiles. The Planning Portal says its parts let the roof span the building and:
"transfer the loads (weight) created by any wind and snow down to the walls."Planning Portal, Building Regulations: Work to an existing roof, read 13 October 2026
Each entry below gives the part's name, what it does and what to look for in a survey: the common problem, written as something to check, not a diagnosis. Whether a part has failed, and why, is for the surveyor to judge on site.
Safety first
Look from the ground, a ladder, the roof space or a drone where you can. HSE's advice is that all roofs, once fixed, "should be treated as fragile until a competent person has confirmed that they are non-fragile". The rooflights section has more.
Pitched roof structure
The frame under the tiles.
Rafters
The sloping timbers that form the pitch of the roof. They run from the wall plate at the eaves up to the ridge, and carry the battens and the covering. The Planning Portal describes them as the timbers that "form the main pitch to the roof".
What to look for: a dip or sag in the roof line, split or rotted timbers, and signs of insect attack, seen from the roof space.
Ridge
The top line of a pitched roof, where two slopes meet. Inside, a ridge board usually runs along the top, with the rafters fixed to it on both sides. Outside, ridge tiles cap the joint (see coverings).
What to look for: a ridge line that dips or bows along its length.
Purlins
Long timbers that run along the roof, usually about halfway up the rafters, and act like beams to support them. In the Planning Portal's words, they "reduce the span (unsupported length) of the rafters". Angled timbers called struts often prop the purlins from a load-bearing wall below.
What to look for: purlins that bend, struts that have been cut or taken out, often during a loft conversion, and splits at the joints.
Ties and ceiling joists
Ties stop the two slopes of a roof spreading apart. The ceiling joists often do this job, or a tie is fixed higher up the rafters. Ceiling joists mainly carry the ceiling below.
What to look for: ties or struts that have been removed, and walls at the eaves that lean outwards, which can follow roof spread.
Wall plate
A timber laid along the top of the outside wall, where the feet of the rafters sit. It spreads the weight of the roof along the wall.
What to look for: rot at the eaves, often where a gutter has overflowed for years, and how well the plate is held down to the wall.
Trusses
Factory-made triangular frames, spaced along the roof, that do the work of rafters, ceiling joists and ties in one. Common in newer houses and extensions, with thin diagonal timbers inside each frame.
What to look for: trusses that have been cut, for example to make room for storage or a hatch, and missing bracing. Treat any cut truss as one for a structural engineer to look at.
Hips
The sloping outside corner where two roof slopes meet, running down from the ridge to the eaves. A hipped roof slopes on all its sides.
What to look for: loose or missing hip tiles and cracked mortar along the hip.
Valleys
The opposite of a hip: the inside corner where two slopes meet and the rain from both runs together. The valley is lined with lead, a preformed liner or purpose-made valley tiles.
What to look for: leaves and moss, splits in the lining and slipped tiles along the valley. A valley carries more water than the slopes beside it, so a small gap matters.
Battens
Thin timber strips fixed across the rafters. The tiles or slates hang on them or are nailed to them.
What to look for: rotted or broken battens, seen from the roof space or where tiles have slipped.
Underlay
A sheet laid over the rafters, under the battens, as a second line of defence against rain and snow that blows past the covering. Older roofs may have bitumen felt, often called sarking felt; newer ones often have a breathable membrane. Very old roofs may have none at all.
What to look for: torn or sagging underlay, felt that has rotted away at the eaves, and daylight or staining seen from the roof space.
Coverings
The layer that keeps the rain out.
Roof covering
The outer layer of the roof: tiles, slates, metal sheets or a membrane. In a report, "roof coverings" usually means this whole layer, with the ridge, hips and edges named in the notes.
What to look for: slipped, cracked or missing pieces, moss, and earlier repairs in a different material.
Tiles
Clay or concrete units hung on battens. Plain tiles are small and laid with a double overlap. Interlocking tiles are larger and lock into the tiles beside them.
What to look for: slipped, cracked or missing tiles, clay faces that are flaking, and tiles that have lost their nibs or nails.
Slates
Thin, flat units of natural stone or man-made fibre cement, nailed to battens and laid with an overlap. Natural slate is common on older buildings.
What to look for: slipped or cracked slates, metal strips called tingles holding slates that have slipped before, and slipping across a whole slope, which can point to the nails failing (often called nail sickness).
Ridge and hip tiles
Shaped tiles that cap the ridge and the hips, closing the joint where two slopes meet. They are traditionally bedded in mortar. Many newer roofs hold them with a dry ridge or dry hip system instead (see edges and details).
What to look for: loose or missing ridge tiles, cracked or missing mortar, and gaps under the tiles.
Solar panels
Panels fixed above the covering on brackets that pass between the tiles, or set into the roof in place of tiles.
What to look for: cracked or lifted tiles round the brackets, leaves or nests trapped under the panels, and loose cables.
Edges and details
The edges, the joints and the way water leaves.
Eaves
The lower edge of a pitched roof, where it overhangs the wall and drains into the gutter.
What to look for: underlay that has rotted at the eaves, gaps where birds can get in, and staining on the wall below.
Verge
The sloping edge of a roof at a gable, where the roof stops at the side of the building.
What to look for: cracked or missing mortar under the edge tiles, and loose tiles along the verge, which take the full force of the wind.
Fascia
The board fixed along the eaves, to the ends of the rafters. The gutter is usually fixed to it.
What to look for: rot, flaking paint, and a fascia that has pulled away, taking the gutter with it.
Soffit
The board on the underside of the overhang at the eaves, closing the gap between the fascia and the wall. It may carry vents that air the roof space.
What to look for: gaps where birds get in, blocked vents, and staining from a gutter that overflows.
Bargeboard
The board fixed along the verge of a gable, covering the ends of the roof timbers. It does at the gable what the fascia does at the eaves.
What to look for: rot, especially at the lower ends, and loose fixings.
Gutters
The channel along the eaves that collects rain from the roof. Half-round, square and ogee shapes are common, in plastic, cast iron or aluminium. Larger buildings may have box gutters or valley gutters set into the roof itself.
What to look for: blockages, leaking joints, sagging lengths and water that runs the wrong way. On a box gutter, check the lining and the outlet.
Downpipes
The vertical pipes that carry water from the gutters down to the drains. Gutters and downpipes together are often called rainwater goods.
What to look for: blocked pipes, cracked or missing sections, loose brackets, and staining on the wall behind, which can show a leak.
Flashings
Strips of lead or another material that seal the joint where a roof meets a wall, a chimney or anything else that stands up from it. The top edge is usually tucked into a mortar joint in the wall. A joint between a roof and a wall is called an abutment.
What to look for: flashings that have lifted, split or come out of the joint, and mortar fillets used in place of a flashing, which often crack.
Lead work
Lead sheet shaped on site to form flashings, valley linings, soakers and the coverings of small roofs and bays. A stepped flashing follows a sloping wall in steps. Soakers are small pieces slipped under each tile where the roof meets a wall.
What to look for: splits and cracks, lead that has slipped or crept down the slope, missing fixings, and signs of theft.
Mortar bedding
Sand and cement used to bed ridge and hip tiles and to seal the verge. It holds the tiles in place and closes the gaps under them.
What to look for: cracked or missing mortar and loose tiles. Mortar often wears out before the tiles it holds, so patchy repairs are common.
Dry ridge and dry verge systems
Fixings that hold ridge, hip and verge tiles with clips, screws and plastic caps in place of mortar. They are common on newer roofs and after re-roofing.
What to look for: missing or broken caps, loose clips, and units that have shifted in the wind.
Valley linings
The waterproof lining of a valley, in lead, a preformed liner or valley tiles. The valley itself is described under pitched roof structure.
What to look for: splits in the lead, cracked mortar along the edges of the valley, and leaves and moss building up.
Chimneys
From the stack to the pot.
Chimney stack
The part of the chimney that stands above the roof, usually brick or stone, carrying one or more flues.
What to look for: a stack that leans, open or worn mortar joints, cracked render, and loose bricks near the top.
Chimney pots
The clay or concrete pots on top of the stack, usually one for each flue.
What to look for: cracked or loose pots, and pots that have been capped, which suggests the flue below is out of use.
Flaunching
The sloping bed of mortar on top of the stack that holds the pots in place and sheds rain off the top.
What to look for: cracks and missing pieces. Water that gets in through cracked flaunching can work down into the stack.
Cowls and caps
Fittings on a pot that keep out rain and birds, help the flue draw, or close off a flue that is no longer used.
What to look for: loose, damaged or missing cowls and caps.
Chimney flashings
Where the stack passes through the roof, flashings seal the joint: an apron at the front, stepped flashings and soakers at the sides, and a small back gutter behind the stack on the uphill side.
What to look for: lifted or split lead, and staining on the chimney breast in the roof space below.
Flat roofs
A flat roof, layer by layer.
A flat roof is built up in layers. From the bottom: the joists or other structure, the deck, often a vapour control layer, the insulation and the waterproofing. The Planning Portal describes a simple flat roof as joists spanning between two walls, covered by panels which are then covered "in felting or other such coatings". Where the insulation sits gives the roof its type: warm, cold or inverted.
Deck
The boards or slab that carry the roof: timber boards, plywood, OSB, metal decking or concrete.
What to look for: soft or springy spots underfoot, where it is safe to walk, sagging between joists, and staining on the ceiling below.
Vapour control layer
A sheet laid on the warm side of the insulation to limit how much moist air from inside the building gets into the roof, where it could condense.
What to look for: it is rarely visible. Condensation or staining under the roof, with no leak found above, is a reason to ask what the build-up is.
Insulation
Boards or quilt that keep the building warm. In a flat roof it may sit above the deck, below it, or on top of the waterproofing.
What to look for: boards that feel soft or crushed underfoot, and any record of what was used. Its condition is usually hidden until a core is cut.
Waterproofing membrane
The continuous layer that keeps the water out. The main types are:
- Felt, or built-up roofing: layers of bitumen sheet bonded together, often with a mineral or chipping finish on top.
- Single ply: one sheet of plastic or rubber, such as PVC, TPO or EPDM, with welded or taped joints.
- Liquid applied: a coating brushed or rolled on in layers, often with a reinforcing fleece, and often laid over an old roof.
- Mastic asphalt: a layer laid hot and smoothed by hand, common on older and commercial roofs.
What to look for: splits, blisters, ridges, open seams, crazing on asphalt, standing water and patch repairs. Note the type, because the right repair depends on it.
Upstands
The membrane turned up the face of a wall, parapet or rooflight kerb, so water cannot get in at the joint. The top is usually covered by a flashing or a coping.
What to look for: upstands that are very low, peeling away or split at the corners, and missing cover flashings.
Outlets
The openings that drain water off a flat roof into a downpipe: either down through the roof, or out through a parapet wall by a scupper or chute.
What to look for: blocked or missing grates, splits in the membrane round the outlet, and water standing nearby.
Falls
The slight slope built into a flat roof so that water runs to the outlets. A flat roof is never quite flat.
What to look for: ponding, which is water left standing long after rain. It can point to too little fall, a sagging deck or a blocked outlet.
Parapets
A low wall that rises above the edge of a roof, round a flat roof or along a gable.
What to look for: cracked render or brickwork, plants growing from the joints, and damp on the inside face below.
Copings
The capping along the top of a parapet wall, in stone, concrete, clay or metal, shaped to throw water clear of the wall.
What to look for: cracked, loose or moved copings, and open joints between them.
Warm roof
The insulation sits above the deck and under the waterproofing, with a vapour control layer below it. The deck stays on the warm side of the insulation.
What to look for: the build-up as recorded on drawings or found in a core, so the report says which type the roof is.
Cold roof
The insulation sits below the deck, between or under the joists, so the deck is on the cold side. It relies on a ventilated gap above the insulation to carry moisture away.
What to look for: blocked or missing vents, and condensation or mould on the underside of the deck.
Inverted roof
The insulation sits on top of the waterproofing, held down by gravel or paving slabs, so the membrane is protected underneath.
What to look for: insulation boards or gravel that have shifted. The membrane is hidden, so leaks are harder to trace.
Rooflights
Let the light in, keep the water out.
Rooflight
A window set into a roof to let daylight in. On flat roofs these are often domes or flat glazed units on a raised kerb. On pitched roofs, roof windows sit in the slope. Sheeted roofs often have clear sheets laid in line with the metal sheets.
What to look for: cracked, crazed or yellowed glazing, failed seals, and splits where the membrane meets the kerb.
Kerb
The raised frame that a flat-roof rooflight sits on. The membrane is dressed up its sides as an upstand.
What to look for: splits in the membrane at the corners of the kerb, and rot in timber kerbs.
Rooflights and safety
HSE lists rooflights among the surfaces likely to be fragile, particularly those in the roof plane that can be "difficult to see in certain light conditions or when hidden by paint". It also says falls through fragile surfaces, particularly fibre-cement roofs and rooflights, account for 22% of all fall from height fatal injuries in the construction industry.
"All roofs, once fixed, should be treated as fragile until a competent person has confirmed that they are non-fragile."HSE, Fragile surfaces, page dated 30 October 2024
In a report, note where every rooflight is, so anyone going onto the roof later knows. A view from below, from a safe edge or from a drone avoids standing near them.
Metal and sheet roofs
Sheets, panels and what holds them.
Profiled sheets
Steel or aluminium sheets pressed into ribs or corrugations for strength, fixed to purlins. Common on industrial, warehouse and farm buildings.
What to look for: rust, flaking coating, dents and holes, and sheets lifting at the edges. HSE lists corroded metal sheets as likely to be fragile.
Composite panels
Two metal skins with insulation bonded between them, made and fixed as one panel. Sometimes called sandwich panels.
What to look for: gaps at the joints between panels, rust at the edges, and skins parting from the insulated core.
Built-up sheeted roofs
An outer sheet and an inner liner sheet with insulation between them, put together on site. HSE lists liner panels on built-up sheeted roofs as likely to be fragile.
What to look for: the same as profiled sheets on the outside, and staining or rust on the liner seen from inside.
Fibre cement sheets
Corrugated sheets of fibre cement, found on many older industrial and farm buildings. HSE lists non-reinforced fibre-cement sheets as likely to be fragile, whatever their profile.
What to look for: cracks, broken corners, moss and lichen. Check the asbestos register before anyone works on or near them.
Cut edges
The edges of a sheet where it was cut to length, usually at the eaves and the end laps. The protective coating stops at the cut, so rust often starts there and creeps back under the coating.
What to look for: rust and peeling coating along the lower edge of the sheets at the eaves, often called cut edge corrosion.
Fixings
The screws or bolts that hold the sheets to the purlins, each with a sealing washer under the head.
What to look for: rusty, loose or missing fixings, and perished or missing washers. Each one is a possible way in for water.
Laps
Where one sheet overlaps the next: side laps along the ribs, and end laps where one sheet meets the next one up the slope. Laps are sealed with a strip of sealant or tape.
What to look for: laps that have opened, rust at the end laps, and sealant that has dried out or squeezed out.
HSE also warns that no sheeted roof, whatever its material, should be trusted to bear a person's weight, and that this includes the ridge and the purlins.
Naming parts in a report
How a roof report names the parts.
Most roof reports take the roof one part at a time, in the same order every time, with a rating, photos and a note for each part. The part names are usually broad groups, with the detail in the note:
- Roof coverings: tiles, slates, sheets or membrane, with the ridge, hips, verges, valleys and flashings named in the note.
- Roof structure: rafters, purlins, trusses, battens and underlay, as seen from the roof space.
- Chimney stacks: the stack, pots, flaunching, cowls and chimney flashings.
- Rainwater pipes and gutters: gutters, downpipes and outlets.
- Rooflights, parapets and solar panels, where the roof has them.
Within each part, name the exact place: "rear slope, above the bedroom window", "north-east outlet", "left-hand verge". Write what was seen, then what to check or do, and how soon. Where a part could not be seen or reached, say so and say why.
Our roof inspection report example and template shows this layout in full, with a checklist for the visit. For the rest of the building, see our building condition survey guide.
Before a repair: building regulations in England
The Planning Portal says that repairing or re-covering an existing pitched or flat roof will not normally need a building control application if less than 25 per cent of the total building envelope and less than 50 per cent of the roof are affected. It says approval is needed if those limits are exceeded, for structural alterations, if a new covering will perform significantly differently in a fire, or if a new covering adds 15 per cent or more to the weight of the roof covering.
That is the Planning Portal's guidance for England. Elsewhere in the UK, or if in doubt, ask the local building control or building standards office before the work starts.
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More guides
Guides for the rest of the survey.
Questions
Parts of a roof, answered.
What are the main parts of a roof?
On a pitched roof: the structure (rafters, purlins, ridge, wall plate or trusses), the battens and underlay, the covering of tiles or slates, and the edges and details (eaves, verges, fascias, soffits, gutters, downpipes and flashings), plus any chimney. On a flat roof: the deck, the insulation, the waterproofing membrane, and the upstands, outlets, parapets and copings.
What is the difference between the eaves and the verge?
The eaves are the lower, level edge of a pitched roof, where the gutter runs. The verge is the sloping edge at a gable, where the roof stops at the side of the building.
What is the difference between a fascia, a soffit and a bargeboard?
The fascia is the board along the eaves that usually carries the gutter. The soffit is the board underneath the overhang, between the fascia and the wall. The bargeboard runs along the verge of a gable, covering the ends of the roof timbers.
What is flaunching on a chimney?
The sloping bed of mortar on top of a chimney stack that holds the pots in place and sheds rain. Cracked flaunching is a common finding, and water can work down into the stack through it.
What is the difference between a warm roof and a cold roof?
It is about where the insulation sits. In a warm roof it sits above the deck, so the deck stays warm. In a cold roof it sits below the deck, with a ventilated gap above it. In an inverted roof it sits on top of the waterproofing.
What does roof covering mean in a report?
The outer layer that keeps the rain out: tiles, slates, metal sheets or a flat-roof membrane. Reports usually rate the covering as one part and name the ridge, hips, verges, valleys and flashings in the notes.
Do I need building regulations approval to re-cover a roof?
Sometimes. In England, the Planning Portal says a repair or re-cover will not normally need a building control application below set limits, and will need approval above them or for structural work and some changes of covering. Our summary above gives the limits. Check with your building control body if in doubt.
Is it safe to walk on a roof to inspect it?
Only with the right precautions and access. HSE's advice is that all roofs, once fixed, should be treated as fragile until a competent person has confirmed they are not, and rooflights are a particular hazard. Inspect from the ground, a ladder, the roof space or a drone where you can.
Sources
Where the facts come from.
The quoted roof parts and the building regulations summary come from the Planning Portal; the safety facts come from HSE. Both were read on 13 October 2026. The other definitions and the "what to look for" notes are our own plain-English summary of common trade terms, not official guidance. This guide is not legal advice: check the latest position before relying on it.
- Building Regulations: Work to an existing roof, Planning Portal, guidance for England, no date shown.
- Fragile surfaces, Health and Safety Executive, page dated 30 October 2024.
- Roof work, Health and Safety Executive, page dated 5 June 2026.
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