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Sava Level 6 Surveying study materials
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Sava Level 6 Surveying practice questions

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Question 1Inspection and survey practice

In an automatic level, what is the main function of the compensator?

  1. It illuminates the crosshair and staff for observations made after dark.
  2. It measures the vertical angle so that slope distances can be reduced later.
  3. It magnifies the graduations on the staff so that finer readings can be taken.
  4. It keeps the line of sight horizontal when the instrument is slightly out of level. Correct answer.

Explanation

The compensator is a suspended optical element that automatically maintains a horizontal line of sight once the instrument has been roughly levelled. This removes the need to re-centre a bubble before every staff reading.

Question 2Inspection and survey practice

A backsight of 1.245 m is taken on a benchmark and a foresight of 0.870 m is taken on a change point. What is the level difference to the change point?

  1. 0.425 m rise
  2. 2.115 m rise
  3. 0.375 m fall
  4. 0.375 m rise Correct answer.

Explanation

Level difference is backsight minus foresight: 1.245 − 0.870 = 0.375 m. Because the backsight is the larger reading, the change point is higher than the benchmark, so the difference is a rise.

Question 3Inspection and survey practice

How many seconds of arc are there in one degree?

  1. 3 600 Correct answer.
  2. 60 000
  3. 1 000
  4. 60

Explanation

A degree is divided into 60 minutes of arc, and each minute into 60 seconds, giving 60 × 60 = 3 600 seconds in a degree. This unit is used to express angular misclosure in traverses and the stated accuracy of instruments.

Question 4Inspection and survey practice

What does the abbreviation GNSS stand for in surveying?

  1. Global Network of Surveying Satellites
  2. Geodetic Network of Survey Stations
  3. Global Navigation Satellite System Correct answer.
  4. General Navigation and Survey Standard

Explanation

GNSS is the generic term for satellite positioning systems such as GPS, GLONASS, Galileo and BeiDou. Surveyors use it for control, detail capture and setting out where sky visibility is adequate.

Question 5Inspection and survey practice

In surveying, what is a benchmark?

  1. A permanent mark with a known reduced level Correct answer.
  2. The difference between the first and last staff readings
  3. The position where the level instrument is set up
  4. A temporary peg placed at the end of each level run

Explanation

A benchmark is a stable, permanent physical mark whose height above a chosen datum is known, and it forms the starting point or check for levelling. It should be robust and unlikely to be disturbed by construction or traffic.

Question 6Inspection and survey practice

On a plan drawn at a scale of 1:500, a line measures 1 mm. What distance does this represent on the ground?

  1. 500 m
  2. 5 m
  3. 50 m
  4. 0.5 m Correct answer.

Explanation

A scale of 1:500 means one unit on the plan represents 500 of the same units on the ground. Therefore 1 mm represents 500 mm, which is 0.5 m.

Question 7Inspection and survey practice

A traditional theodolite is designed primarily to measure which quantity?

  1. Horizontal and vertical angles Correct answer.
  2. Barometric pressure differences
  3. Ground vibration levels
  4. Slope distances between two points

Explanation

The theodolite consists of a telescope mounted on horizontal and vertical circles, allowing precise measurement of horizontal and vertical angles. Distance measurement requires separate equipment such as a tape or an electronic distance meter.

Question 8Inspection and survey practice

What is the principal purpose of a traverse survey?

  1. To establish horizontal control from measured angles and distances Correct answer.
  2. To transfer a level datum across a wide river using reciprocal observations
  3. To determine the depth of a proposed foundation before excavation begins
  4. To measure the area of an irregular parcel of land to the nearest square metre

Explanation

A traverse runs a series of connected lines between stations, measuring the angles and distances at each station to establish horizontal control. The resulting coordinates can then be used as a framework for detail survey or setting out.

Question 9Inspection and survey practice

A level run of 1.2 km closes with a misclosure of +0.024 m. The specification permits a misclosure of 12√K mm, where K is the length in kilometres. Which statement is correct?

  1. The misclosure is acceptable only if the run is shortened.
  2. The misclosure exceeds the permitted value and the run should be investigated. Correct answer.
  3. The misclosure is exactly at the permitted value and needs no action.
  4. The misclosure is within the permitted value and can be distributed.

Explanation

The permitted misclosure is 12 × √1.2 ≈ 13 mm, so the observed 24 mm is roughly twice the allowance. The run therefore fails the specification and the likely cause, such as a booking or staff error, should be found before repeating or adjusting the work.

Question 10Inspection and survey practice

What does a resection determine in a control survey?

  1. It checks the collimation error of a level by two-peg testing.
  2. It fixes the position of the instrument from observations to known points. Correct answer.
  3. It transfers a level datum from one side of a river to the other.
  4. It fixes the coordinates of detail points by radiating from a known station.

Explanation

In a resection the instrument is set up on an unknown point and observations are taken to at least three known control stations. The angles or distances are used to compute the coordinates of the instrument station, allowing work to start without occupying a control point.

Question 11Inspection and survey practice

Why must an atmospheric correction be applied to distances measured by an electronic distance meter?

  1. The prism constant changes with temperature and must be updated.
  2. The instrument's optical axis bends more in warm air.
  3. The speed of light in air varies with temperature and pressure. Correct answer.
  4. The curvature of the Earth increases with rising humidity.

Explanation

An EDM measures the travel time of a light or microwave signal, and the speed of that signal depends on air temperature, pressure and humidity. The instrument applies a correction from these parameters so that the reported slope distance matches the true distance.

Question 12Inspection and survey practice

The interior angles of a five-sided closed traverse sum to 539°59'20". What is the angular misclosure?

  1. +1'20"
  2. +40"
  3. -20"
  4. -40" Correct answer.

Explanation

For a closed polygon the interior angles should sum to (2n − 4) × 90°, which for n = 5 is 540°. The observed sum is 40 seconds less than 540°, so the misclosure is −40 seconds.

Question 13Inspection and survey practice

A surveyor must record the profile of a vertical retaining wall beside a busy road where there is no safe access behind the wall. Which technique is most suitable?

  1. Photogrammetry from satellite imagery of the area
  2. GNSS RTK observations taken from the top of the wall
  3. A tape and offset survey using a long steel tape
  4. Reflectorless total station observations taken from the roadside Correct answer.

Explanation

A reflectorless total station measures directly to the wall surface, so the surveyor can stay at a safe distance and still capture points at different heights. It also gives angular and distance data that can be reduced to coordinates or a profile.

Question 14Inspection and survey practice

What is the primary purpose of an as-built survey?

  1. To record the position and level of completed work against the design Correct answer.
  2. To locate buried services before excavation takes place
  3. To establish the original design levels before construction begins
  4. To transfer control points from the national grid to the site

Explanation

An as-built survey records the actual position, level and dimensions of constructed elements so that they can be compared with the design. It is used to identify departures from specification and to feed accurate information into record drawings.

Question 15Inspection and survey practice

Why is secondary control usually derived from primary control rather than from independent GNSS observations at each point?

  1. It keeps all stations in a single consistent coordinate system and datum. Correct answer.
  2. It reduces the number of prisms required for the survey.
  3. It removes the need for a levelling loop around the site.
  4. It allows each station to be observed in the most convenient order.

Explanation

Deriving lower-order stations from an established higher-order framework preserves internal consistency, so all coordinates and levels share one datum and one set of errors. Independent observations at each point can introduce small inconsistencies between adjacent stations.

Question 16Inspection and survey practice

Why are trial holes used in an underground utility survey?

  1. To measure the electrical resistance of the service pipe
  2. To confirm the position, depth and type of buried services Correct answer.
  3. To provide a permanent record of the service for the asset owner
  4. To establish the depth of the water table at the site

Explanation

A trial hole, or slit trench, exposes the service so that its exact position, depth, material and size can be verified directly. This is the highest-confidence evidence available in a utility survey and is used to validate geophysical tracing results.

Question 17Inspection and survey practice

A total station is set up over a station and a backsight is taken to a reference target. What is the main purpose of this backsight?

  1. To measure the height of the instrument above the station
  2. To orientate the instrument to the survey coordinate system Correct answer.
  3. To check the level of the prism pole at the backsight
  4. To record the temperature for atmospheric correction

Explanation

The backsight establishes the direction of the reference object, allowing the instrument to relate every subsequent horizontal angle to the chosen coordinate system. Without a correct orientation, all detail or setting-out bearings would be systematically wrong.

Question 18Inspection and survey practice

A steel tape calibrated at 20 °C is used to measure a distance on a day when the tape temperature is 32 °C. How does this affect the measured distance?

  1. Too short, so a negative correction is applied
  2. Too short, so a positive correction is applied Correct answer.
  3. Too long, so a negative correction is applied
  4. Unaffected, because steel has a low expansion coefficient

Explanation

Steel expands as it warms, so at 32 °C the tape is longer than its calibrated length and each tape length covers more ground than it should. The recorded distance is therefore too small, and the correction is added.

Question 19Inspection and survey practice

Which document provides the most direct evidence that a total station is fit for precise work on a project?

  1. The site diary entry for the day of the survey
  2. The survey specification issued by the client
  3. The current calibration certificate for the instrument Correct answer.
  4. The manufacturer's brochure for the instrument

Explanation

A calibration certificate records when the instrument was tested against traceable standards and confirms that its angle and distance results are within the maker's tolerance. It is the routine evidence relied on in quality audits and disputes.

Question 20Inspection and survey practice

For a level sight of 200 m, what is the approximate combined effect of curvature and refraction?

  1. 2.7 mm too small
  2. 0.7 mm too small
  3. 2.7 mm too large Correct answer.
  4. 27 mm too large

Explanation

The combined correction is approximately 0.0675D² metres with D in kilometres. For D = 0.2 km this gives 0.0027 m, and because refraction bends the line of sight downwards less than curvature raises it, the staff reading is too large by about 2.7 mm.

Question 21Inspection and survey practice

A closed traverse of perimeter 800 m has a linear misclosure of 0.080 m. What is the precision ratio?

  1. 1:1 000
  2. 1:100 000
  3. 1:100
  4. 1:10 000 Correct answer.

Explanation

Precision is the misclosure divided into the total length: 800 ÷ 0.080 = 10 000. The traverse therefore closes to a precision of about 1:10 000, which is often quoted as the relative accuracy of the framework.

Question 22Inspection and survey practice

A specification requires detail to be plotted to within 0.5 mm at a scale of 1:1000. What ground tolerance does this represent?

  1. 0.50 m Correct answer.
  2. 5.0 m
  3. 0.10 m
  4. 0.05 m

Explanation

The plotting tolerance is multiplied by the scale denominator: 0.5 mm × 1000 = 500 mm, or 0.50 m on the ground. This figure sets the accuracy standard that the field observations must achieve.

Question 23Inspection and survey practice

A total station is quoted as ±(2 mm + 2 ppm). For a measured distance of 500 m, what is the uncertainty contributed by the ppm term alone?

  1. 2.0 mm
  2. 0.2 mm
  3. 0.5 mm
  4. 1.0 mm Correct answer.

Explanation

Two parts per million of 500 m is 2 × 500 ÷ 1 000 000 metres, which equals 0.001 m or 1.0 mm. The full uncertainty also includes the constant 2 mm term, giving about 3 mm in total.

Question 24Inspection and survey practice

Which statement about heights obtained by GNSS RTK is correct?

  1. RTK heights are relative to the antenna phase centre only.
  2. RTK heights are ellipsoidal and need a geoid model to give levels. Correct answer.
  3. RTK heights are orthometric and need no further correction.
  4. RTK heights are measured above the nearest benchmark.

Explanation

GNSS positioning yields heights above the reference ellipsoid, whereas engineering levels are normally expressed above a geoid-based datum such as mean sea level. A geoid model is therefore applied to convert ellipsoidal heights to orthometric heights.

Question 25Inspection and survey practice

What is the most appropriate first action on arriving at a site to begin a topographic survey?

  1. Begin measuring the building facade from the pavement
  2. Set up the instrument on the first available control point
  3. Download the previous survey data from the office server
  4. Carry out a site risk assessment and confirm access arrangements Correct answer.

Explanation

Before any equipment is set up, the surveyor should identify hazards, confirm the scope of access and check that any permits or escort arrangements are in place. This protects the team and avoids work being stopped or repeated later.

Question 26Inspection and survey practice

On a topographic survey drawing, what does a contour line represent?

  1. A line marking the boundary between two property parcels
  2. A line showing the steepest descent path from a ridge
  3. A line joining points of equal horizontal distance from a station
  4. A line joining points of equal elevation on the ground Correct answer.

Explanation

A contour line is the locus of points at the same reduced level, so it shows the shape and slope of the terrain. Close spacing indicates steep ground, while wide spacing indicates gentler ground.

Question 27Inspection and survey practice

In a detail survey, what is an offset?

  1. The angular difference between true north and grid north on a drawing
  2. The perpendicular distance from a survey line to a detail point Correct answer.
  3. The temperature correction applied to a steel tape during measurement
  4. The vertical distance between two successive instrument stations

Explanation

An offset is measured perpendicular from a survey line or baseline to a detail point, allowing that point to be plotted relative to the line. Offsets are usually kept short and taken at right angles to reduce plotting error.

Question 28Inspection and survey practice

What is the main purpose of establishing a site datum before setting out engineering works?

  1. To provide a fixed reference elevation and position for setting out Correct answer.
  2. To provide a temporary secure storage point for survey instruments and tools
  3. To record the names and roles of survey personnel working on site
  4. To replace the need for a permanent control survey on the site

Explanation

A site datum is a fixed reference with known coordinates or level, traceable to project control, from which dimensions and elevations are set out. It gives all parties a common basis for construction.

Question 29Inspection and survey practice

A surveyor sets out a design point by polar coordinates from an occupied control station. Which pair of values must be calculated from the control and design coordinates?

  1. Ellipsoidal height and geoid separation
  2. Horizontal distance and bearing (azimuth) Correct answer.
  3. Slope distance and vertical angle only
  4. Grid convergence and scale factor only

Explanation

Polar setting out computes the horizontal distance and bearing from the occupied station to the design point, then turns the required angle and measures that distance. Slope distance and vertical angle are used only for a direct 3D measurement and still require reduction.

Question 30Inspection and survey practice

In a leveling survey, a backsight of 1.452 m is taken to a benchmark with a reduced level of 50.000 m. The foresight to a new point is 1.876 m. What is the reduced level of the new point?

  1. 49.576 m Correct answer.
  2. 49.624 m
  3. 52.328 m
  4. 50.424 m

Explanation

The height of instrument is benchmark RL plus backsight: 50.000 + 1.452 = 51.452 m. The new reduced level is HI minus foresight: 51.452 - 1.876 = 49.576 m.

Question 31Inspection and survey practice

A slope distance of 250.00 m is measured between two points, and the slope angle is 5° from horizontal. What is the horizontal distance between the points?

  1. 249.05 m Correct answer.
  2. 21.83 m
  3. 250.00 m
  4. 250.96 m

Explanation

The horizontal distance is the slope distance multiplied by the cosine of the slope angle: 250.00 × cos 5° = 249.05 m. Slope reduction is required before the distance is used in a horizontal plan.

Question 32Inspection and survey practice

A total station has a stated horizontal angle uncertainty of ±5″. At a sighting distance of 300 m, what lateral position error does this angular uncertainty produce, approximately?

  1. 2.4 mm
  2. 7.3 mm Correct answer.
  3. 0.7 mm
  4. 24.0 mm

Explanation

Convert the angular uncertainty to radians: 5 arcseconds is about 5/206265 = 2.42 × 10^-5 rad. Lateral error is then 300 m × 2.42 × 10^-5, which is about 0.0073 m or 7.3 mm.

Question 33Inspection and survey practice

When applying the Bowditch (compass) rule to adjust a closed traverse, what is the underlying assumption about the errors in the traverse?

  1. All lines have equal error regardless of length
  2. Angular errors are negligible and only distances need adjustment
  3. Errors are proportional to the square root of the line length
  4. Linear errors are distributed in proportion to each leg length Correct answer.

Explanation

The Bowditch rule distributes the closing errors in latitude and departure in proportion to the length of each leg. It assumes that random errors in angles and distances accumulate in a way roughly proportional to leg length.

Question 34Inspection and survey practice

In a repeated precise leveling program for deformation monitoring, which approach best separates real ground movement from random measurement noise?

  1. Compare changes with propagated uncertainty and keep stable reference benchmarks Correct answer.
  2. Adjust each campaign independently to the first campaign's coordinates
  3. Accept any change greater than the smallest staff graduation as real movement
  4. Use a different instrument for every campaign so errors cancel

Explanation

A change should be judged against the propagated uncertainty of the height difference, not against a single reading resolution. Stable reference benchmarks and a consistent measurement procedure are needed so that apparent movement is not caused by datum instability or changed instruments.

Question 35Building pathology, defects and repair

Which set of features most strongly indicates rising damp in a ground-floor masonry wall?

  1. Damp patches high on the wall beneath a window, drying in dry weather
  2. Local dampness around a leaking gutter, with algae on the eaves and fascia
  3. Dampness at the base, a horizontal tide mark, and salts near the skirting Correct answer.
  4. Uniform dampness across the wall after heavy rain, drying from the edges

Explanation

Rising damp is groundwater-derived moisture drawn upward through the wall by capillary action, so it is concentrated near the base and often leaves a tide mark and hygroscopic salts. Rain penetration and leaks usually produce localized or upper-wall dampness rather than a basal band with salts.

Question 36Building pathology, defects and repair

Which feature is most characteristic of dry rot (Serpula lacrymans) in structural timber?

  1. Cuboidal cracking of the timber with rusty-red spore dust nearby Correct answer.
  2. Dark, wet timber with no visible fruiting body or spore dust at all
  3. Small exit holes with fine wood dust beneath the timber surface
  4. A white, cotton-wool-like fungal growth that remains soft when dry

Explanation

Serpula lacrymans produces cuboidal cracking of the timber, pancake-like fruiting bodies and rusty-red spores, and it can spread through masonry. Exit holes and fine dust indicate wood-boring insects rather than dry rot.

Question 37Building pathology, defects and repair

What is the primary cause of surface condensation on a cold internal wall?

  1. Hygroscopic salts absorbing moisture from the surrounding room air
  2. Water vapour in warm air reaches a surface below its dew point Correct answer.
  3. Moisture rising through the wall from the ground beneath the floor
  4. Rainwater penetrating a defective external render finish on the wall

Explanation

Condensation occurs when air containing water vapour is cooled below its dew point at a cold surface. Rising damp, rain penetration and hygroscopic salts are separate moisture sources, although they can add to internal humidity.

Question 38Building pathology, defects and repair

Efflorescence on a brick or masonry wall is best described as what?

  1. A green algal growth favored by shaded damp conditions
  2. A white salt deposit left when moisture evaporates from the surface Correct answer.
  3. A dark stain caused by mould growing on damp plaster
  4. A soft, powdery decay of the brick face caused by repeated frost action

Explanation

Soluble salts dissolved in water are carried to the surface and crystallize as the water evaporates, producing a white bloom. It is not necessarily a defect in itself but indicates moisture movement and can recur if the source is not addressed.

Question 39Building pathology, defects and repair

How does frost action most commonly damage clay bricks?

  1. Frost dissolves the brick's soluble salts and leaves a white deposit
  2. Freezing draws moisture out of the brick and causes internal shrinkage cracks
  3. Ice forms only on the outer surface and polishes the brick face smooth
  4. Water in the brick pores freezes and expands, causing the face to spall Correct answer.

Explanation

Water occupying pores expands by about 9% on freezing, generating internal pressure that can detach the brick face. Repeated freeze-thaw cycles worsen the damage, especially in saturated or frost-susceptible bricks.

Question 40Building pathology, defects and repair

Why does corrosion of reinforcing steel often cause concrete to spall?

  1. The steel expands only after the concrete has carbonated completely
  2. Rust occupies more volume than steel and generates bursting pressure Correct answer.
  3. The steel shrinks and pulls the surrounding concrete inward
  4. Corrosion consumes the cement paste directly around the reinforcing steel

Explanation

Corrosion products occupy several times the volume of the parent steel, so expansive pressure builds up and cracks or detaches the cover concrete. Carbonation and chlorides are common triggers because they destroy the passive layer.

Question 41Building pathology, defects and repair

What is the usual repair for weathered, recessed mortar joints in an exposed brick wall?

  1. Applying a thin coat of cement paint over the joints
  2. Raking out the loose mortar and repointing with a compatible mortar Correct answer.
  3. Replacing the affected bricks with harder, frost-resistant engineering bricks
  4. Sealing the joints with a flexible silicone sealant

Explanation

Recessed joints are cut back to sound mortar and refilled with a mortar compatible with the masonry, restoring weathertightness. Cement paint or sealant can trap moisture and are not durable pointing repairs.

Question 42Building pathology, defects and repair

A roof leak appears at the junction of two roof slopes in a valley. Which detail is most likely at fault?

  1. The ridge ventilation is blocked by debris and restricts airflow
  2. The valley flashing or lining is incorrectly installed or blocked Correct answer.
  3. The gutter bracket spacing is too wide
  4. The roof felt has insufficient laps at the eaves and is torn in places

Explanation

A valley concentrates rainwater, so its lining or flashing must be continuous, correctly lapped and kept clear of debris. Ridge ventilation, gutter brackets and eaves laps do not directly seal the valley junction.

Question 43Building pathology, defects and repair

What is a common visible result of sulfate attack on brickwork and mortar?

  1. A green stain spreading across the lower brick faces near the ground
  2. Uniform shrinkage of the mortar joints with no discoloration
  3. Softening of the brick only at the top of the wall
  4. Expansion and cracking, often with white deposits at the joints Correct answer.

Explanation

Sulfates react with cement hydration products to form expansive compounds such as ettringite, causing cracking, spalling and white deposits. It typically occurs where sulfate-bearing ground water or bricks contact Portland cement mortar.

Question 44Building pathology, defects and repair

Carbonation of concrete is significant mainly because it does what?

  1. Increases the concrete's compressive strength permanently and rapidly
  2. Raises the pH of the concrete and passivates the steel
  3. Prevents chloride ions from entering the concrete
  4. Lowers the pH at the steel and allows corrosion to start Correct answer.

Explanation

Carbon dioxide reacts with calcium hydroxide, reducing the concrete's pH; when the carbonation front reaches the steel, the passive film is lost and corrosion can proceed. Carbonation does not prevent chloride ingress, and it does not provide permanent protection.

Question 45Building pathology, defects and repair

Which condition most directly promotes chloride-induced corrosion of reinforcement?

  1. Reinforcement exposed to marine salts or de-icing salt Correct answer.
  2. Concrete kept permanently wet with pure water
  3. A dry, sheltered internal floor slab with no wetting
  4. Concrete with a high cement content and low permeability

Explanation

Chlorides break down the passive oxide film on steel even at high pH, so marine exposure and de-icing salts are major risks. High cement content and low permeability reduce, rather than promote, chloride ingress.

Question 46Building pathology, defects and repair

Alkali-silica reaction (ASR) in concrete typically produces which pattern of damage?

  1. Map cracking with gel exudation and expansion of the concrete Correct answer.
  2. A single vertical crack below a lintel
  3. Localized pitting around embedded nails
  4. Uniform surface wear with no internal expansion or gel formation

Explanation

ASR forms an expansive gel from reactive silica and alkali pore solution; it causes map or random cracking and may exude gel. The damage is internal and widespread rather than a single structural crack.

Question 47Building pathology, defects and repair

What is a typical consequence of corroded cavity wall ties in a cavity wall?

  1. Rising damp caused by a blocked air brick near the base of the wall
  2. Settlement of the internal floor joists and ground floor
  3. Efflorescence on the inner leaf only near the ceiling
  4. Cracks and bulging of the outer leaf, with loss of restraint Correct answer.

Explanation

Corroding ties expand and crack the mortar around them; severe corrosion can reduce restraint and allow the outer leaf to bulge or become unstable. Air bricks and floor joists are unrelated to tie corrosion.

Question 48Building pathology, defects and repair

Mould repeatedly forms along the line of a concrete lintel on an internal wall. What is the most likely explanation?

  1. The wall has no damp-proof course at all
  2. The plaster contains too much lime
  3. The lintel forms a cold bridge, so moist air condenses there Correct answer.
  4. Hygroscopic salts have been carried up from the foundation into the wall

Explanation

Concrete lintels can conduct heat across the wall more readily than surrounding masonry, creating a colder internal surface where condensation and mould occur. A continuous damp-proof course and salts would produce a different, usually basal, pattern.

Question 49Building pathology, defects and repair

Interstitial condensation occurs when water vapour does what?

  1. Diffuses into a construction and reaches dew point within it Correct answer.
  2. Is absorbed by hygroscopic plaster and released in summer
  3. Condenses on the inner surface of a single-glazed window
  4. Is blown into a roof space through an open vent

Explanation

Vapour moving through a wall or roof can cool below its dew point inside the construction, where it condenses out of sight. This differs from surface condensation, which forms on visible room-side surfaces.

Question 50Building pathology, defects and repair

A diagonal crack in brickwork is wider at the top on one side of a bay and narrows toward the base. What is the most likely cause?

  1. Expansion of the brickwork due to thermal growth and solar heating
  2. Sulfate attack in the mortar joints
  3. Differential foundation movement, such as local subsidence Correct answer.
  4. Frost action within the pores of the bricks and mortar

Explanation

Diagonal cracking that tapers indicates one part of the foundation has moved relative to another; the widest part often locates near the movement. Thermal and moisture movements tend to produce more regular or horizontal/vertical patterns.