Defect Atlas — Roofing & Rainwater Goods

An individual slate or tile that has moved from its original lapped position on the roof slope.

Unit hanging below its course, exposing the unit beneath or the underlay where visible from ground or access level.

Fixing failure, batten decay, wind uplift or thermal movement may contribute.

• location on the slope and orientation
• number of units affected
• whether the displaced unit is retained or has fallen
• any visible underlay or batten beneath

“A slipped slate was recorded on the south slope, third course from the eaves, with the underlay visible beneath.”

Absence of one or more units from the roof covering.

Gap in the lapped pattern; exposed underlay, batten or interior where visible.

Storm damage, prior slippage, fixing loss or unrecorded earlier intervention can be associated.

• location and number of missing units
• whether replacement units are stored on site
• visibility of the underlay or interior
• any associated debris at eaves or ground level

“Two missing slates were recorded on the north slope above the porch, with exposed underlay visible from ground level.”

A slate or tile raised at its tail or head, no longer sitting flat against the unit beneath.

Unit visibly raised; daylight or shadow gap beneath the tail when viewed from low angle.

Wind exposure, lost or corroded fixings, distortion of supporting battens may contribute.

• extent across the slope
• association with exposed elevations or roof edges
• whether multiple adjacent units are affected
• any associated displacement of mortar bedding

“Lifted tiles were recorded along the west verge, with visible gaps beneath several tails consistent with wind exposure.”

Movement, slippage or rotation of ridge tiles, hip tiles, or stone or terracotta cappings.

Visible misalignment of the ridge line; opened joints; cracked or missing bedding mortar.

Failed bedding mortar, lack of mechanical fixing, wind action or thermal movement may contribute.

• extent and location along the ridge
• condition of bedding mortar where visible
• any cracked or missing ridge units
• any associated leakage indicators internally

“A displaced ridge tile was recorded toward the eastern end of the main ridge, with open bedding joints visible from access level.”

A slate or tile that is fractured in place but has not yet displaced from its position.

Visible crack across the unit; sometimes with stepped or laminated fracture lines; fragments may be present.

Impact, foot traffic, frost action, manufacturing defects or thermal stress may contribute.

• location and crack orientation
• whether fragments remain in place or have fallen
• any associated water staining below internally
• evidence of foot-traffic damage along access routes

“A cracked tile was recorded mid-slope on the south elevation, with a transverse fracture running across the visible face.”

A roof slope showing visible deflection, undulation or loss of plane.

Plane of the slope no longer straight when sighted along the eaves or ridge; localised hollows or swells.

Rafter, purlin or batten movement, overloading from re-covering, decay of supporting timbers, or historic deformation may contribute.

• extent and location of deflection
• association with chimneys, valleys or party walls
• any visible internal evidence
• whether the deflection appears longstanding or recent

“Sagging was observed across the central bay of the main slope, with a visible dip between the chimneys when sighted along the ridge.”

Separation of natural slate along its bedding planes.

Visible layering; lifted laminae at exposed edges; thinning or flaking of the upper surface.

Weathering, frost cycling, atmospheric pollution and inherent slate quality can be associated.

• extent and distribution across the slope
• association with exposed or sheltered areas
• evidence of laminae loss
• any associated fixing exposure

“Slate delamination was recorded across the upper courses of the east slope, with visible lifting of upper laminae on several units.”

Fracturing of slates through the body of the unit, often along bedding planes.

Visible split lines; sometimes with displacement of the lower fragment.

Weathering, frost, fatigue at nail holes or impact damage may contribute.

• extent and pattern of splitting
• association with nail line
• any displaced fragments
• comparison with adjacent unaffected slates

“Slate splitting was observed across several units of the south slope, with visible cracks running parallel to the nail line.”

Loss of material from the tail, side or head edges of slates.

Ragged, thinned or rounded edges; loss of original cut profile.

Long-term weathering, run-off, pollution and age may contribute.

• extent across the slope
• implications for lap and water-shedding
• any associated water marking below
• comparison with sheltered units

“Edge erosion was recorded along the tails of slates across the west slope, with visible thinning of the original cut edges.”

General surface deterioration of slate including softening, pitting or loss of finish.

Dull, pitted or roughened surface; sometimes with surface flaking or powdering.

Atmospheric pollution, weathering, inherent slate quality and orientation may contribute.

• extent and distribution
• any associated fixing visibility
• presence of surface deposits
• comparison between elevations

“Surface decay was observed on slates across the south-west slope, with a visibly pitted and softened upper face.”

Iron-oxide staining radiating from the nail or fixing line of slates.

Brown or orange stain on the slate face, often vertical or fanning from the nail hole.

Corrosion of ferrous nails or hooks may be associated; staining can indicate fixing deterioration.

• extent and number of units affected
• any associated slippage
• type of fixing where visible
• association with particular elevations

“Rust staining was recorded at the nail line of slates across the north slope, consistent with corrosion of ferrous fixings.”

Loss of surface fragments from clay or concrete tiles.

Pitted, flaked or chipped surface; loss of glaze or fired skin where present.

Frost action, manufacturing variability, salt activity or weathering may contribute.

• extent across the slope
• depth of loss where visible
• any associated cracking
• comparison between exposed and sheltered units

“Spalling was observed on clay tiles along the lower courses of the west slope, with pitted surfaces and small surface losses.”

Separation of layers within clay or concrete tiles.

Visible layered structure; lifting or detachment of upper layer; sometimes with hollow sound under tap if access permits.

Manufacturing flaws, frost cycling or long-term weathering may contribute.

• number and location of affected tiles
• extent of layer separation
• any associated loss of fragments
• evidence of fallen material below

“Tile lamination was recorded on several units of the south slope, with the upper layer visibly lifted from the body of the tile.”

Loss of applied coatings or surface finishes on concrete or coated tiles.

Loss of original colour or finish; exposed aggregate or substrate; patchy weathered appearance.

Weathering, UV exposure and age of original coating may contribute.

• extent across the slope
• any colour variation suggesting different replacement batches
• associated surface roughening
• evidence of biological colonisation

“Surface coating loss was observed across concrete tiles on the main slope, with visible exposure of the aggregate substrate.”

Damage to tiles that can be associated with freeze-thaw cycling.

Surface flaking, pitting or fracturing; sometimes concentrated on exposed elevations or units retaining moisture.

Saturation, exposure, frost cycling and tile porosity may contribute.

• association with exposed elevations
• extent and severity
• any associated moss or debris retention
• comparison with sheltered areas

“Damage consistent with frost action was recorded on tiles along the exposed north-east verge.”

Fracturing of ridge or hip tiles in place.

Visible cracks across the ridge unit; sometimes with displaced fragments.

Movement, impact, thermal stress or failed bedding may contribute.

• location along the ridge or hip
• number of units affected
• whether fragments are loose
• any associated bedding mortar loss

“A cracked ridge tile was recorded on the western end of the main ridge, with visible transverse fracture.”

Progressive downhill movement of lead sheet due to repeated thermal cycling on bays of excessive length.

Buckling, ridging or rippling of the lead sheet; movement away from upper edges; sometimes with splitting at fixings.

Excessive bay length, lack of free movement provision or undersized lead may contribute.

• extent and location
• any associated splitting
• approximate bay length where measurable
• evidence of internal water staining

“Lead creep was observed across the central flat of the porch roof, with visible ridging and downward movement away from the upstand.”

Fracturing of lead sheet, typically running across the slope or along fixings.

Linear cracks through the lead sheet; sometimes with associated creep or buckling.

Thermal fatigue, creep, restraint at fixings or undersized lead may contribute.

• crack location and length
• association with bay edges or fixings
• any visible water entry path
• extent of movement across the bay

“A lead split was recorded across the central bay of the gutter lining, running approximately 200 mm along the line of thermal movement.”

A lead flashing, soaker or apron that has moved from its original detailed position.

Lifted, drooping or detached flashing; gap between flashing and adjacent fabric.

Wind action, failed wedging, mortar loss in chase, or thermal movement may contribute.

• location of displacement
• size and direction of gap
• condition of chase mortar where visible
• any associated internal staining

“A displaced lead flashing was recorded at the chimney junction, with the upper edge lifted from the chase and a visible gap of approximately 15 mm.”

Loss or cracking of a mortar fillet used at a roof junction in lieu of proper lead detailing.

Open joint between covering and adjacent abutment; missing or cracked mortar fillet; sometimes with visible underlay or substrate.

Drying shrinkage, thermal movement, inherent incompatibility of mortar fillets as a weathering detail may contribute.

• location and extent
• any associated internal water staining
• whether a flashing was originally present
• evidence of prior re-fillet repair

“An open mortar fillet was recorded at the abutment between the lean-to roof and the main wall, with the fillet largely missing across its length.”

Disruption of the protective patina on lead sheet, often associated with run-off pathways.

White or pale crystalline deposits on lead surfaces; tracking patterns following run-off lines.

Run-off from concrete, lichen-covered slopes or organic acids can be associated with patina disruption.

• extent and pattern
• source of run-off where identifiable
• any associated staining of adjacent fabric
• comparison with sheltered lead surfaces

“Patination disruption was observed on the lead flat below the moss-covered slate slope, with white deposits tracking from the eaves.”

Localised damage to lead at gutter outlets, chute openings or rainwater connections.

Cracked, torn or deformed lead at the outlet edge; loose or missing collar; debris build-up.

Movement, blockage pressure, frost expansion of trapped water or inadequate detailing may contribute.

• location and outlet type
• extent of damage
• any associated blockage
• evidence of internal staining below

“Damaged lead was recorded at the parapet gutter outlet, with a torn collar and visible debris around the chute.”

Decay or failure of timber battens supporting roof units, often visible where units are displaced or removed.

Soft, friable or fungus-affected timber visible behind displaced units; surface decay or staining.

Moisture ingress, fungal decay or insect activity may contribute.

• extent visible from accessible areas
• any associated displacement of units
• evidence of dampness or staining
• type of timber where identifiable

“Decayed battens were observed behind a slipped slate on the north slope, with visibly soft and discoloured timber.”

Corrosion of nails, hooks, clips or other fixings securing roof units.

Rust staining around fixings; visible loss of fixing section where accessible; associated unit slippage.

Use of incompatible or non-stainless fixings, moisture exposure and age may contribute.

• extent and distribution
• type of fixing where identifiable
• any associated unit displacement
• evidence of prior re-fixing

“Corroded fixings were recorded across the south slope, with rust staining at multiple nail positions and several associated slipped slates.”

A tile clip, slate hook or supplementary fixing that has failed in service.

Broken, missing or distorted fixing; associated unit lifting or slipping.

Material fatigue, corrosion, wind loading or inappropriate original specification may contribute.

• number and location of failed fixings
• associated unit movement
• type of clip or hook
• exposure of the affected area

“Failed slate hooks were recorded along the verge, with associated lifting of three adjacent units.”

A fixing arrangement that appears insufficient for the exposure or material, observed without testing.

Sparse, irregular or inconsistent fixing pattern visible where units are displaced or stripped; mixed original and replacement fixings.

Earlier informal repair, inappropriate original specification, or modification over time may be associated.

• evidence of mixed fixing types
• any pattern variation across the slope
• association with displaced units
• exposure rating of the location

“An inconsistent fixing pattern was observed where slates were lifted on the south slope, with both original nails and later clips visible.”

Deterioration of the underlay membrane visible through gaps in the covering.

Torn, brittle, sagging or perished underlay material; visible daylight where applicable.

Age, UV exposure, repeated wetting or animal disturbance may contribute.

• extent visible from accessible points
• any associated water ingress
• type of underlay where identifiable
• evidence of patch repair

“Deteriorated underlay was observed behind a missing slate on the porch roof, with visibly brittle and torn material.”

A gutter run obstructed by debris, vegetation or accumulated material.

Visible debris, vegetation or silt within the gutter channel; standing water; overflow staining beneath.

Leaf fall, biological growth, lack of maintenance or undersized outlet may contribute.

• location and extent of blockage
• any associated overflow staining
• evidence of vegetation growth
• condition of outlets

“A blocked gutter run was recorded along the eastern eaves, with visible debris accumulation and overflow staining on the wall below.”

Loss of fall, deflection or downward movement of a gutter run.

Visibly deflected gutter line when sighted along the eaves; standing water; gap between gutter and fascia.

Failed or missing brackets, decayed fascia or rafter feet, or overloading from debris may contribute.

• extent and location of sag
• any associated bracket failure
• evidence of standing water
• condition of supporting timberwork

“A sagging gutter section was recorded along the south eaves, with a visible dip between two brackets and standing water along the run.”

A joint in a gutter run showing visible water loss.

Water staining beneath the joint; visible dripping during or after rainfall; failed sealant or jointing material.

Movement, sealant failure, corrosion at the joint or original installation may contribute.

• joint location and type
• extent of associated staining
• any prior repair evidence
• associated discharge onto fabric below

“A leaking gutter joint was recorded mid-run on the north elevation, with vertical staining on the masonry below.”

Corrosion of cast iron, steel or aluminium gutter sections.

Rust staining, surface pitting, holes or perforation; flaking coating; sometimes with structural weakening.

Coating failure, retained debris, age or atmospheric exposure may contribute.

• extent and location
• any visible perforation
• condition of any protective coating
• associated staining below

“Corrosion was recorded along the cast iron gutter on the west elevation, with surface pitting and a small visible perforation near a joint.”

A downpipe that is blocked, broken, displaced or otherwise not conveying water as intended.

Visible damage, splits or missing sections; overflow at top; staining or saturation of adjacent wall; vegetation at outlet.

Frost expansion of trapped water, impact damage, corrosion or blockage may contribute.

• location and nature of damage
• extent of associated wall staining
• any blockage visible at base or hopper
• discharge location at ground

“A damaged downpipe was recorded on the eastern elevation, with a split section above the offset and saturation of the wall below.”

A rainwater hopper that is damaged, blocked, leaking or overflowing.

Debris accumulation, corrosion, displacement, cracked side or overflow staining around the hopper.

Blockage, undersized capacity, corrosion or damage may contribute.

• extent of debris
• any associated overflow staining
• structural condition of the hopper
• fixing condition

“A defective hopper was recorded at second-floor level on the north elevation, with overflow staining extending down to the cornice below.”

A rainwater fitting, bracket, ear or section that is missing or detached.

Loose or fallen components; uncoupled lengths; pipe held only by friction or paint.

Corrosion of fixings, masonry loss at fixings, or impact damage may contribute.

• location and component type
• stability of remaining components
• any associated wall damage
• ground-level debris

“A detached downpipe bracket was recorded at first-floor level, with the pipe unsupported across approximately one metre.”

Rainwater discharging directly onto a building element rather than into the drainage system.

Saturation, staining, biological growth or erosion of the fabric beneath the discharge point.

Failed or absent rainwater goods, displaced flashings or design issues may contribute.

• source of discharge
• extent of saturation
• associated material loss or biological growth
• any internal damp associated

“Discharge onto fabric was recorded below a missing downpipe section, with visible saturation and moss growth on the wall beneath.”

Visible staining on an internal ceiling that may be associated with water entry through the roof above.

Brown, yellow or tide-mark staining on ceiling finishes; sometimes with associated surface deformation.

Defective covering, flashing failure, blocked gutters or condensation may contribute; visual observation alone does not confirm a single source.

• location and pattern of staining
• any associated active dampness
• relationship to roof features above
• evidence of repeated or single events

“Ceiling staining was recorded directly beneath the chimney stack, with a tide-marked pattern consistent with intermittent water entry.”

Damp marking on internal or external fabric adjacent to a roof abutment.

Staining, salt blooming or biological growth following the line of an abutment, parapet or party wall.

Flashing failure, mortar fillet loss, parapet defect or cavity tray issues may contribute.

• location along the abutment
• extent above and below
• evidence of recent or longstanding dampness
• condition of associated flashings

“Damp staining was recorded internally along the line of the lean-to roof abutment, with a marked tide line below the ceiling.”

Damp expression on internal or external walls in association with a parapet.

Staining, salt blooming, biological growth or finish failure on internal faces below parapet level; sometimes with external indicators.

Coping defects, parapet cracking, DPC failure, or absent cavity trays may contribute.

• internal and external location
• condition of coping or capping
• any visible movement
• evidence of cyclical wetting

“Penetrating damp expression was recorded internally beneath the parapet on the east elevation, with associated salt blooming on the plaster surface.”

Visible wetting, dampness or staining of exposed roof timbers viewed from a roof void or accessible interior.

Darkened, wet or stained timber surfaces; sometimes with associated fungal growth or efflorescence.

Active leaks, condensation or sustained dampness may contribute.

• location and extent
• relationship to covering details above
• any associated decay indicators
• ventilation condition of the roof void

“Wet roof timber was observed in the western bay of the roof void, with darkened areas across the rafter beneath the valley.”

Visible standing water in gutter linings, parapet gutters or roof valleys.

Persistent water in horizontal surfaces; associated debris or staining of the lining.

Loss of fall, blockage, settlement or lining deformation may contribute.

• extent and depth of standing water
• any associated lining damage
• outlet condition
• evidence of overflow internally

“Standing water was recorded in the parapet gutter behind the north elevation, with associated debris around the outlet.”

Visible moss growth on roof slopes, ridges or in joints between units.

Green, brown or yellow cushions of moss across the covering or along ridges; sometimes with associated debris build-up.

Shaded orientation, retained moisture, surface texture and lack of maintenance may contribute.

• extent and distribution
• association with shaded elevations
• any associated displacement of units
• evidence of gutter blockage from dislodged moss

“Moss colonisation was recorded across the north slope, with cushions visible along ridge joints and at slate laps.”

Lichen growth on slates, tiles, leadwork or stone copings.

Circular or irregular patches of yellow, white, grey or orange lichen on the covering surface.

Atmospheric conditions, exposure and surface texture may contribute.

• extent and species pattern where identifiable
• association with particular elevations
• any associated surface decay
• ecological considerations

“Lichen colonisation was recorded across the south slope, with mature patches across exposed tiles.”

Higher plant growth — including seedlings, grasses or shrubs — established on roof areas.

Visible plants rooted in joints, gutters, parapets or behind flashings.

Debris accumulation, moisture retention and seed deposition may contribute.

• location and size of growth
• evidence of root penetration
• any associated damage to mortar or covering
• presence of nesting wildlife

“Vegetation growth was recorded in the parapet gutter on the east elevation, with grass and a small buddleia rooted in retained debris.”

Build-up of leaves, twigs, dust or other debris in gutters, valleys or behind parapets.

Visible debris within gutter and valley runs; sometimes with associated moss or vegetation growth.

Nearby trees, lack of maintenance or wind-deposited material may contribute.

• location and depth of debris
• any associated blockage
• evidence of associated water retention
• biological colonisation of the debris

“Debris accumulation was recorded in the valley gutter between the main slopes, with retained leaves and moss growth visible from access level.”

Green or dark biological staining on roof or rainwater surfaces.

Greenish, brown or dark biofilm on slates, tiles, leadwork or downpipes.

Sustained dampness, shading and atmospheric conditions may contribute.

• extent and distribution
• association with shaded or damp areas
• evidence of run-off staining
• comparison between elevations

“Algal staining was recorded across the north slope and on the cast iron downpipe below, consistent with sustained dampness.”

Corrosion of cast iron gutter, hopper or downpipe components.

Rust staining, flaking paint, surface pitting; sometimes with section loss or perforation at joints or rear faces.

Coating failure, retained moisture or debris, and age may contribute.

• extent of visible corrosion
• condition of any protective coating
• any associated perforation or section loss
• rear-face condition where accessible

“Corrosion of the cast iron downpipe was recorded across its full height on the north elevation, with rust staining of the masonry behind.”

Corrosion of steel flashings, trims or fascia profiles used in roof and rainwater systems.

Rust expression, coating failure, perforation; sometimes with associated staining of adjacent fabric.

Coating failure, design exposure, contact with dissimilar metals or salt deposition may contribute.

• location and extent
• any associated perforation
• evidence of bimetallic contact
• associated staining

“Steel trim corrosion was recorded along the eaves of the rear extension, with visible rust expression and run-off staining of the fascia.”

Staining of masonry below roof or rainwater elements, often associated with corrosion or material discharge.

Linear stains running vertically below leaks, corroded fittings, lead components or coated surfaces.

Active corrosion, leaching from coatings or discharge from blocked rainwater goods may contribute.

• source of run-off
• extent and intensity of staining
• any associated surface decay of the masonry
• evidence of cyclical wetting

“Run-off staining was recorded on the masonry below the corroded gutter, with linear marking extending down to plinth level.”

Accelerated corrosion of one metal where it is in contact with another, observed at roof or rainwater junctions.

Localised corrosion concentrated at junctions between dissimilar metals; sometimes with associated staining.

Galvanic action between dissimilar metals in the presence of moisture may contribute.

• location and identity of metals where possible
• extent and severity of corrosion
• any associated detachment or leakage
• evidence of original or later detailing

“Accelerated corrosion was recorded at the junction between the steel fixing and the lead flashing, with localised pitting on the steel face.”

Use of sealant, mastic or bitumen on roof or rainwater components in lieu of proper repair detailing.

Visible black, grey or coloured sealant smeared across joints, flashings, lap edges or rainwater fittings.

Earlier short-term repair, lack of access for specialist work, or inappropriate materials selection may be associated.

• location and extent
• any visible failure or detachment of the sealant
• underlying defect that may have prompted the repair
• compatibility with adjacent materials

“Sealant repair was recorded across the lead flashing at the chimney junction, with visible bitumen smeared along the upper edge.”

Replacement slates, tiles or ridge units that differ visibly from the original covering.

Mismatched colour, profile, size or material of replacement units; sometimes with visible pattern disruption.

Earlier repair using available rather than matching units may contribute; matching original units may be unavailable.

• extent and distribution of replacements
• differences in profile, colour or material
• any associated performance issues
• implications for significance

“Inappropriate replacement tiles were recorded across the central south slope, with units of differing colour and profile to the surrounding original covering.”

A localised patch repair to lead sheet, flashing or apron.

Visible patch of differing lead thickness or appearance; sometimes with soldered or burned joints; differing patina.

Earlier repair of splits, holes or damaged sections may be associated.

• location and extent
• type of jointing used where identifiable
• any associated current defects
• evidence of subsequent failure of the patch

“A patch repair was recorded in the central bay of the lead flat, with a visibly different lead colour and joint line.”

Use of hard cement-rich pointing in the chase of lead flashings.

Dense grey pointing visible along the chase; sometimes with associated cracking, loss or displacement of the flashing.

Earlier maintenance using cement mortar may be associated; cement can be inappropriate for traditional lead detailing.

• extent and location
• any associated cracking of the pointing
• evidence of flashing displacement
• condition of adjacent masonry

“Cement-rich pointing was recorded along the chase of the chimney flashing, with associated cracking and partial displacement of the lead.”

Heavy paint accumulation on rainwater goods that obscures condition or impairs function.

Thick, layered, blistered or peeling paint on gutters, hoppers and downpipes; sometimes obscuring rust, joints or fittings.

Repeated maintenance painting over earlier failed systems may contribute.

• extent of paint accumulation
• evidence of failure of paint layers
• any obscured defects
• implications for assessment

“Painted-over rainwater goods were recorded on the north elevation, with multiple layers of paint obscuring joint and bracket condition.”

A rainwater good installed without sufficient fall, or otherwise out of correct alignment.

Standing water along the gutter, reverse fall, or visibly inconsistent line; sometimes with overflow staining.

Original installation, settlement, or subsequent re-fixing may be associated.

• extent and location
• evidence of standing water
• associated discharge issues
• fixing arrangement

“A gutter section appeared to lack adequate fall along the east eaves, with standing water observed along the run.”

Evidence of earlier repair, alteration or intervention to roof or rainwater elements for which no record is available.

Mismatched materials, irregular details, partial repair lines or anomalous fixings without supporting documentation.

Phased historical repair, undocumented maintenance or piecemeal renewal may be associated.

• location and nature of the apparent intervention
• extent across the roof
• any associated current defects
• implications for understanding original detailing

“Evidence of an unrecorded earlier intervention was observed at the east verge, where the lead detail differs from that elsewhere on the roof and no records are available.”