Defect Atlas — Mortars, Pointing & Joints

A masonry joint in which mortar is missing or significantly recessed, leaving the joint open to weather.

Voids between adjacent units, exposing the depth of the joint; sometimes with debris, vegetation or water staining within.

Erosion, loss of pointing, weathering or earlier raking out without subsequent repointing may contribute.

• extent and distribution of open joints
• depth of opening where assessable
• presence of debris or vegetation within
• association with sheltered or exposed aspects

“Open joints were recorded along the lower courses of the south elevation, with mortar absent to a depth of approximately 30 mm.”

Mortar pointing that has lost surface material and recessed below the original joint face.

Soft, rounded or pitted mortar surface set back from the masonry face; sometimes with associated friability.

Weathering, water flow, original mix composition and sustained exposure may contribute.

• extent and depth of erosion
• association with exposure or run-off paths
• friability of remaining mortar
• evidence of progression

“Eroded pointing was recorded across the upper string course, with the mortar surface set back approximately 10 mm from the masonry face.”

Pointing that sits below the surrounding masonry face, whether by design, erosion or earlier intervention.

Mortar visibly set back from the arrises of surrounding units; sometimes with shadow lines emphasising the recess.

Original detailing, weathering or past raking out may contribute.

• depth and consistency of recess
• evidence of whether the recess is original or developed
• condition of adjacent arrises
• any associated water retention

“Recessed joints were recorded across the rebuilt panel, with the pointing consistently set back behind the arrises of the surrounding stones.”

Pointing that is detaching or capable of being dislodged from the joint without significant force.

Visible cracking around the perimeter of the pointing; movement under light pressure; sometimes with fragments fallen from the joint.

Loss of adhesion, salt activity, frost cycling or incompatible mortar may contribute.

• extent of loose pointing
• size of detaching fragments
• evidence of associated decay in adjacent fabric
• stability under environmental conditions

“Loose pointing was recorded along the lower courses, with fragments lifting on light hand pressure.”

Joints from which pointing is absent over a meaningful area, exposing bedding mortar or voids behind.

Open joints with no surface pointing; sometimes with bedding mortar visible behind, sometimes with voids.

Loss over time, raking out without repointing or earlier failure may contribute.

• extent and location of missing pointing
• depth of joint exposed
• condition of bedding mortar where visible
• presence of voiding behind

“Missing pointing was recorded across the gable, with joints open and bedding mortar visible behind.”

Mortar that crumbles, releases material on light handling or has lost cohesion through its body.

Soft, easily disaggregated material; loss under light pressure; sometimes with associated powdering.

Original mix, prolonged weathering, salt activity or biological action may contribute.

• extent and depth of friability
• evidence of associated salts or moisture
• method used to assess friability
• stability of adjacent fabric

“Friable mortar was recorded across the parapet joints, releasing material on light pressure.”

Mortar surface releasing fine, dust-like material indicating loss of binder cohesion at the surface.

Light residue on adjacent surfaces or hands when touched; chalky, dulled surface; sometimes with very gradual recession.

Loss of binder, weathering, salt activity or biological action may contribute.

• extent and distribution of powdering
• evidence of associated salts or moisture
• stability of underlying mortar
• association with specific orientations or areas

“Powdering mortar was recorded on the south-facing pointing, with light residue transferring to the hand on touch.”

Loss of the sharp edge of masonry units adjacent to joints, often associated with hard pointing or weathering.

Rounded or chipped arrises along bed or perpend joints; sometimes with widened joint width compared with adjacent areas.

Hard or proud pointing concentrating stress at arrises, weathering, frost or impact may contribute.

• extent and distribution of arris loss
• association with hard pointing or specific joint profiles
• approximate widening of joints
• evidence of progression

“Loss of arris was recorded along the upper bed joint, consistent with stress concentration at the adjacent over-hard pointing.”

Joints that have become wider over time through erosion, arris loss or repeated repointing.

Wider joints than typical for the assembly; sometimes with chipped or eroded arrises; visible variation between historic and adjacent areas.

Erosion, repeated raking out, frost cycling or arris damage may contribute.

• approximate joint widths recorded against typical original widths
• extent of widening
• condition of surrounding masonry units
• evidence of progression

“Joint widening was recorded across the rebuilt panel, with bed joints noticeably wider than those in the surrounding original fabric.”

Vertical perpend joints from which pointing is absent or significantly recessed.

Open vertical voids between units; sometimes consistently across courses; may admit water and debris.

Erosion, original workmanship or selective failure of perpends may contribute.

• extent and location of open perpends
• depth and width of openings
• any associated water tracking visible internally
• comparison with adjacent bed joints

“Open perpends were recorded across the upper section, with vertical joints consistently set back from the surrounding bed joints.”

Cracks within mortar pointing, ranging from fine surface fissures to wider cracks passing through the joint.

Linear cracks within the pointing, sometimes following the joint, sometimes diagonal across it.

Shrinkage, movement, frost cycling, incompatibility with adjacent fabric or thermal effects may contribute.

• orientation, width and length of cracks
• association with bed or perpend joints
• any associated displacement
• evidence of progression

“Cracked pointing was recorded across the upper courses, with fine longitudinal cracks following the bed joints.”

Very fine cracks within pointing, often only visible on close inspection or in raking light.

Thin linear marks following the joint or radiating across the pointing; sometimes confined to surface skin.

Drying shrinkage of recent pointing or minor seasonal movement may contribute.

• extent and distribution of hairline cracking
• association with recently repointed areas
• depth where assessable
• evidence of progression

“Hairline joint cracking was recorded across the recently repointed bay, visible in raking light along several bed joints.”

A stepped crack pattern following alternating bed and perpend joints, often associated with structural movement.

Cracks following the path of least resistance through the mortar joints, producing a stair-step pattern across the masonry.

Differential settlement, foundation movement or wall plate movement may contribute.

• extent, length and width of cracking
• direction of the step pattern
• any associated displacement across the crack
• evidence of progression

“Stepped cracking through the joints was recorded above the window head, with the pattern rising diagonally across approximately 1.2 m of masonry.”

Cracks associated with drying shrinkage of mortar, often within recently repointed areas.

Cracks along the centre or edges of the pointing; sometimes with debonding from adjacent masonry units.

Mix composition, application thickness, drying conditions or substrate suction may contribute.

• location and pattern of cracking
• association with recent repointing
• evidence of debonding at joint edges
• stability of cracked pointing

“Mortar shrinkage cracking was recorded along the centre of the recently repointed joints, with associated debonding visible at the upper arris.”

Visible displacement or opening at a bed joint, suggesting differential movement between courses.

Wider or stepped opening along a specific bed joint; sometimes with associated cracking through adjacent units.

Structural movement, slip planes, bedding-mortar behaviour or load redistribution may contribute.

• location, length and width of the opening
• any vertical or lateral displacement
• extent across the elevation
• evidence of progression

“Movement at the bed joint was recorded above the lintel, with the joint opening consistently along its length.”

Evidence at the joint of slippage, opening or distress along a bedding plane within the assembly.

Linear opening or displacement at a specific horizontal plane; sometimes with associated mortar loss or unit displacement.

Bedding mortar performance, slip planes within multi-leaf walls or differential loading may contribute.

• location and extent of bedding-plane distress
• any displacement above and below the plane
• evidence of moisture or salt activity along the plane
• stability of the wall section

“Bedding-plane weakness was recorded at the third course above ground level, with consistent opening of the bed joint along the elevation.”

White or pale crystalline deposits emerging from mortar joints, indicating salt movement to the surface.

Powdery or feathery white deposits on or adjacent to the joint; sometimes with associated friability.

Salt content within mortar or adjacent fabric mobilised by moisture cycling may contribute.

• extent, location and pattern of efflorescence
• association with specific aspects, levels or sources of moisture
• any associated mortar friability
• evidence of recurrence after cleaning

“Salt efflorescence at the joints was recorded along the lower courses, with crystalline deposits emerging consistently after wet weather.”

Darkened, persistently damp areas of mortar joint indicating sustained moisture presence.

Joints visibly darker than surrounding areas; sometimes with adjacent biological growth or staining.

Rainwater ingress, run-off paths, rising moisture or condensation may contribute.

• extent and location of damp staining
• association with rainwater goods, copings or details
• evidence of associated biological growth or salts
• variation with weather or season

“Damp joint staining was recorded below the failed rainwater outlet, extending across approximately 0.5 m of pointing.”

White, drip-like deposits emerging from mortar joints associated with calcium carbonate run-off.

White or cream calcareous streaks below joints, sometimes forming stalactite-like deposits in sheltered locations.

Sustained water passage through lime-based mortar, often associated with leaks or saturation, may contribute.

• location and extent of leaching deposits
• association with leaks, copings or run-off paths
• any associated joint erosion
• evidence of recurrence

“Lime leaching was recorded below the parapet joint, with calcareous streaking extending approximately 200 mm down the masonry face.”

Loss of mortar from joints in patterns consistent with freeze–thaw activity.

Friable or spalled mortar concentrated on exposed faces or at frost-prone details; sometimes with broken-out fragments below.

Saturation followed by freezing, exposure or water retention behind impervious surfaces may contribute.

• location and extent of loss
• association with exposed aspects or water-retaining details
• evidence of seasonal progression
• stability of adjacent fabric

“Frost-related joint loss was recorded on the north-facing parapet, with friable mortar and spalled fragments below the affected joints.”

Loss of bedding mortar behind apparently sound pointing, leaving voids that may admit water.

Pointing intact at the surface but sounding hollow on light tapping; sometimes with associated dampness or salts; voids visible where pointing is broken.

Failure or loss of bedding mortar, water tracking behind pointing or original construction may contribute.

• extent of voiding where audible or visible
• associated dampness or salt activity
• stability of overlying pointing
• any visible signs at the masonry face

“Voiding behind the pointing was recorded at the upper courses, with hollow sound on tapping and dampness emerging at adjacent joints.”

Living organisms colonising mortar joints, ranging from algae and mosses to lichens and small plants.

Green, black or grey colonies within or adjacent to joints; sometimes with associated dampness or debris accumulation.

Moisture retention, sheltered orientation, debris accumulation or porous mortar may contribute.

• type and extent of growth where identifiable
• association with damp or sheltered aspects
• any apparent physical effect on the mortar
• presence of more substantial vegetation

“Biological growth was recorded across the north-facing joints, with moss colonising the recessed pointing along the lower string course.”

Lichens established on mortar surfaces, ranging from crustose patches to leafy or shrubby forms.

Discrete patches of grey, yellow, green or orange growth; sometimes with associated mortar staining or pitting beneath.

Exposure, atmospheric conditions, mortar chemistry and absence of regular cleaning may contribute.

• extent and distribution of lichen
• approximate form where identifiable
• any apparent effect on the mortar surface
• association with specific aspects

“Lichen colonisation was recorded across the upper courses, with patchy crustose growth covering approximately 20 percent of the pointing.”

Plant roots established within joints, with potential to displace mortar and adjacent masonry.

Visible woody or fibrous roots emerging from joints; sometimes with associated displacement of pointing or units.

Established self-seeded vegetation, especially in horizontal or sheltered details, may contribute.

• type of vegetation where identifiable
• extent of root penetration where visible
• any associated displacement of mortar or units
• evidence of ongoing growth

“Root growth was recorded within the parapet joint, with a woody stem displacing the adjacent pointing and lifting a coping unit.”

Accumulated deposits of airborne pollutants and dust darkening mortar joints.

Grey, brown or black soiling concentrated on sheltered faces or under projecting details; sometimes obscuring mortar condition.

Atmospheric exposure, traffic-related particulates or sheltered detailing reducing rain washing may contribute.

• extent and pattern of soiling
• association with sheltered or projecting details
• extent to which soiling obscures underlying condition
• presence of associated crusts

“Atmospheric soiling was recorded across the sheltered face of the cornice, with dark deposits obscuring assessment of the underlying mortar.”

Evidence of insects, birds or small animals nesting, boring or living within mortar joints.

Enlarged or excavated joints; visible nesting material; droppings; bee, wasp or insect activity at specific joints.

Soft or friable mortar, sheltered openings and existing voids may contribute.

• type of activity where identifiable
• extent and location of affected joints
• evidence of ongoing use
• any structural or fabric implications

“Insect activity was recorded at the upper courses, with several enlarged joints showing evidence of solitary bee occupation.”

Pointing using a cement-rich mortar significantly harder than the surrounding historic fabric.

Dense, smooth, grey pointing standing proud or flush, often visibly different in colour and texture from any surviving lime mortar.

Earlier repointing campaigns using Portland cement mortars may contribute.

• extent and location of cement pointing
• evidence of associated decay in adjacent fabric
• comparison with surviving historic mortar where present
• any associated arris loss

“Over-hard cement pointing was recorded across the lower courses, visibly proud of the masonry face and associated with arris loss in the adjacent stones.”

Mortar whose binder, hardness, porosity or appearance is materially different from the surrounding historic fabric.

Visible contrast in colour, texture, hardness or weathering behaviour between the pointing and adjacent original mortar or masonry.

Earlier interventions using mortars selected without reference to the host fabric may contribute.

• extent and pattern of incompatible mortar
• evidence of differential weathering compared with adjacent fabric
• any associated decay or loss in surrounding units
• indicators of binder difference where assessable

“Incompatible mortar was recorded across the central panel, visibly harder and more weather-resistant than the surrounding historic pointing.”

Loss of softer masonry adjacent to harder pointing, often through concentration of weathering on the more vulnerable material.

Erosion, spalling or arris loss in masonry units adjacent to hard pointing, with the pointing itself often intact and standing proud.

Differential hardness directing weathering and moisture movement to the softer fabric may contribute.

• extent and pattern of adjacent fabric loss
• relative hardness of pointing and adjacent units
• evidence of moisture concentration at unit faces
• association with specific exposure

“Hard mortar appears associated with adjacent fabric loss in the sandstone units, with erosion concentrated on the unit faces while the pointing remains standing proud.”

Visible variation in weathering behaviour between adjacent mortars or between mortar and masonry units.

Areas of recession, erosion or staining contrasting with adjacent areas of more resistant material; sometimes following repointing boundaries.

Differing binder, aggregate or mix proportions and differing exposure may contribute.

• extent and pattern of differential weathering
• association with repointing boundaries or specific batches
• evidence of effect on adjacent fabric
• comparison with original fabric where present

“Differential weathering was recorded across the rebuilt section, with the newer pointing visibly more recessed than the surrounding historic mortar.”

Pointing mortar that has been worked or feathered over the face of adjacent masonry units.

Thin films or smears of mortar extending beyond the joint onto the face of the surrounding units; sometimes obscuring tooling or detail.

Workmanship during pointing, inadequate finishing or use of over-wet mixes may contribute.

• extent and distribution of smearing
• extent to which smearing obscures the masonry surface
• any associated decay of masonry beneath
• association with specific repointing campaigns

“Smeared pointing was recorded across the rebuilt panel, with thin films of mortar extending over the faces of several units.”

Pointing finished above the level of the surrounding masonry face.

Mortar standing forward of the masonry surface; sometimes with feathered or rounded edges; may shed water onto unit faces.

Workmanship during pointing, applied to standard joints rather than worn ones, may contribute.

• extent and consistency of proud pointing
• any associated water retention on unit faces
• evidence of arris loss or decay below
• association with specific campaigns

“Proud pointing was recorded across the central elevation, with the mortar standing approximately 3 mm forward of the masonry face.”

Pointing finished as a flat, raised band sitting forward of the joint, often with sharp edges along the masonry units.

Continuous flat strips of mortar standing proud of the masonry, often visually dominant and unlike the surrounding original detailing.

Inappropriate workmanship or finishing techniques applied to historic masonry may contribute.

• extent and location of ribbon pointing
• comparison with adjacent historic profile
• any associated arris damage or water retention
• visual impact on the elevation

“Ribbon pointing was recorded across the lower courses, sitting visibly proud of the masonry and contrasting with the historic pointing above.”

A pointing detail in which mortar strips overlap onto adjacent unit faces, creating a strap-like band across the joint.

Mortar bands extending across the joint and onto the adjacent units, often with sharply defined edges.

Inappropriate workmanship intended to mask wide or eroded joints may contribute.

• extent and location of strap pointing
• extent to which adjacent unit faces are obscured
• any associated water retention or decay beneath
• visual impact compared with surrounding fabric

“Strap pointing was recorded along the upper string course, with broad mortar bands extending across the joints and over the faces of adjacent units.”

A pointing profile that differs from the surrounding historic detailing or is unsuited to the masonry concerned.

Profiles such as weather-struck, bucket-handle or sharply tooled finishes inserted into fabric with different original detailing.

Workmanship reflecting general trade convention rather than the specific historic context may contribute.

• extent and location of the inappropriate profile
• comparison with surrounding historic profile
• any associated water-shedding implications
• visual impact on the elevation

“An inappropriate joint profile was recorded across the rebuilt section, with weather-struck pointing inserted into masonry otherwise finished flush.”

A joint in which pointing has been finished as a concave recess, intentionally or as a result of workmanship.

Concave mortar surface below the level of the surrounding masonry; sometimes with associated water retention or debris accumulation.

Workmanship convention, original detailing or earlier intervention may contribute.

• depth and consistency of the recess
• any associated water retention
• comparison with adjacent profiles
• evidence of associated decay or growth

“Hollow joints were recorded across the lower courses, with mortar consistently set back into shallow concave profiles.”

Pointing from a previous campaign that has lost adhesion, cracked, fallen out or otherwise ceased to perform.

Areas of recently identifiable repointing in poor condition, with cracking, debonding, friability or loss; sometimes contrasting with adjacent better-performing pointing.

Mix incompatibility, workmanship, substrate condition or environmental exposure may contribute.

• extent and location of failed repointing
• type of failure observed
• approximate age of the campaign where known
• evidence of associated decay in adjacent fabric

“Failed repointing was recorded across the lower elevation, with the relatively recent mortar cracked along the joints and friable in places.”

Localised areas of pointing inserted into otherwise older fabric, often as informal maintenance.

Discrete patches of more recent mortar within surrounding original or earlier pointing; sometimes with visibly different colour, texture or hardness.

Phased maintenance or response to localised loss may contribute.

• extent, location and approximate age of patches
• compatibility with surrounding fabric
• condition of patched and surrounding pointing
• evidence of ongoing recurrent loss

“Patch pointing was recorded across the elevation, with several discrete areas of recent mortar inserted into otherwise weathered historic pointing.”

New pointing applied as a surface layer over substantially decayed underlying mortar without proper raking out.

Thin surface skim of newer mortar over a deeper void or friable older mortar; sometimes visible at joint edges or where the skim has broken away.

Cosmetic intervention without adequate preparation may contribute.

• extent of the surface pointing
• evidence of underlying voids or friability
• stability of the skim layer
• any associated dampness within the wall

“Repointing over decayed mortar was recorded along the lower courses, with a thin surface skim concealing voids and friable material behind.”

Evidence that earlier mortar repairs are no longer compatible with surrounding fabric in performance or appearance.

Areas of earlier intervention behaving differently from adjacent fabric: harder, more eroded, more soiled or visibly different in colour.

Earlier choices of binder, aggregate or method may contribute.

• extent and location of identified earlier repairs
• type of incompatibility observed
• any associated decay in adjacent fabric
• evidence of progression

“Previous repair incompatibility was recorded across the upper section, with earlier cement-rich pointing visibly contrasting with the surrounding lime mortar and associated with arris loss.”

Joints filled with flexible sealant rather than mortar, generally inappropriate for historic masonry.

Continuous flexible material within the joint; sometimes discoloured or staining adjacent masonry; often visible as a thin extruded line.

Modern maintenance practice applied to historic fabric may contribute.

• extent and location of sealant-filled joints
• type of sealant where identifiable
• any associated staining of adjacent fabric
• evidence of trapped moisture or salt activity

“A sealant-filled joint was recorded along the parapet coping, with a continuous extruded line of mastic discolouring the adjacent stone.”

Joints or voids filled with modern materials such as expanding foam, mastic, plastic patching compounds or proprietary fillers unsuited to historic fabric.

Foamed, plasticky or otherwise non-mortar material within or behind joints; sometimes visible at joint edges or where surface pointing has broken away.

Informal maintenance using readily available modern products may contribute.

• type of filler where identifiable
• extent and location of use
• any associated decay, dampness or staining
• stability and visibility of the filler

“Inappropriate modern filler was recorded behind missing pointing, with expanding foam visible in the void.”

Loss or significant deterioration of mortar within the bedding plane between courses, with potential structural implications.

Visible voids behind pointing; mortar fragments emerging from joints; sometimes with associated unit displacement or movement.

Long-term weathering, water tracking through walls, salt activity or original mix may contribute.

• extent and depth of bedding mortar loss
• any associated displacement of units
• evidence of moisture or salt activity
• implications for stability

“Failed bedding mortar was recorded along the upper courses, with extensive voiding behind the pointing and minor displacement of two adjacent units.”

Linear staining of mortar joints associated with run-off paths from copings, sills, projections or rainwater goods.

Vertical or diagonal stain marks following run-off paths; sometimes with associated soiling, biological growth or salts.

Failed or inadequate water-shedding details, blocked rainwater goods or saturation may contribute.

• location and extent of staining
• association with identifiable run-off sources
• any associated joint deterioration
• evidence of recurrence

“Water run-off staining was recorded below the displaced coping, with a vertical stain extending across approximately 1 m of pointing.”

Staining of mortar joints by corrosion products from adjacent metalwork or embedded ferrous fixings.

Orange, brown or dark streaks within or below the joint; sometimes with associated displacement around embedded metal.

Corrosion of nearby metalwork, embedded ferrous fixings or run-off from upper details may contribute.

• source of staining where identifiable
• extent and pattern of stained joints
• any associated displacement or cracking
• evidence of active corrosion

“Mortar staining from metal run-off was recorded below the failed iron cramp, with orange streaking extending into the joints below.”

Discolouration of mortar joints by run-off from adjacent materials such as timber, paint, copper, lead or salts from other fabric.

Brown, green, white or coloured staining within or below joints, associated with identifiable upstream sources.

Tannin, pigment, metal or salt run-off from adjacent materials may contribute.

• colour and pattern of staining
• identifiable upstream material
• extent and severity
• evidence of associated damage

“Mortar staining from adjacent materials was recorded below the timber cill, with brown tannin streaks extending across two courses of pointing.”

Damage or disturbance to joints arising from cleaning, scaffolding, fixings, services or other maintenance activity.

Localised chipping, gouging, abrasion or mortar loss at points of maintenance contact; sometimes with associated patch repairs.

High-pressure cleaning, mechanical tools, scaffold contact, drilling for fixings or services installation may contribute.

• location and type of disturbance
• association with identifiable maintenance activity
• extent and severity
• any associated repairs

“Maintenance-related joint disturbance was recorded along the scaffold contact line, with chipped pointing and exposed bedding mortar visible across several joints.”