13 - Building Pathology - General Defects

Question 1

What are historic construction materials and techniques (in NZ)?

Answer 1

Early construction
- Maori construction - Maori used materials found in the forest and swamps, such as wood, bulrush, and stone. They wove materials together without nails.
- Cob construction - Settlers from Britain built cob houses in the 1840s and 1850s using layers of clay, straw, and grass.
- Wooden houses - Timber was the most common material for building houses because of the country’s abundant forests.

Later construction
- Light timber framing - A skeleton of small timbers was covered with weatherboards to create a weatherproof exterior.
- Stone buildings - Stone was used for churches, banks, and public buildings, but was expensive and damaged by earthquakes.
- Concrete, brick, and board - These materials became more common after the 1930s as timber construction became more expensive.
- Prefabricated houses - After World War II, companies produced prefabricated houses using radiata pine and other materials.
- Prefabricated houses - After World War II, companies produced prefabricated houses using radiata pine and other materials.
- Concrete and glass - Modernism - Mid-20th century, modern architectural styles began to appear in commercial buildings
- Art deco - Early 20th century - influencing residential architecture with its streamline forms.

Question 2

What architectural styles are present in New Zealand?

Answer 2

Georgian Style: Pre-colonisation during the 1820s and 1830s.
Victorian: 1837-1901 - NZ architecture followed British and European trends. Most commonly recognised NZ villa.
New Zealand Villa - Most distinctive house types - 1870’s to WW1.
Gothic revival: Villa’s emerged from the 1850’s onwards.
Neo-Classical: This style was popular between 1900 and 1930.
Modernist: This style was introduced in the 1930s.
Californian Bungalow: This single-level wooden building with a verandah became popular in the early 20th century.
Art Deco - early 1930’s and lasted until after WW2.
Modernism - Late 1930’s - Mostley with flat roofs, large expases of glass and very little external decoration. Local architecture - intoduction of mono-pitched roofs, weatherbord cladding, exposed beamsn and rafters and timber linings.
State houseing - Late 1930’s - housing shortage. First constructed in 1937. Mostly single storey detached structures, wth a rectangular footprint, hipped roof, simple multi-pane windows and little to no external decoration.

Post war years
1970’s - Plethora of styles and greater local individuality
1980’s and 90s - Embraced postmodern architecture. 90’s bought increased apartment building in the main centres.
Recent trends - simpler design, clean lines, large areas of glass and minimalist detailing.

Question 3

Name 10 defects you would commonly find in a Georgian building. (UK only)

Answer 3

1. Leaning chimneys
2. Overloading of roof due to change of materials (e.g. concrete tiles)
3. Removal of chimney breasts but not the stack
4. Blocked internal gutters
5. Brick walls prone to distortion due to lack of restraint at each floor level
6. Damp penetration through solid walls
7. Rotting timber joists that are built into external wall
8. Dry rot caused by poor cross-ventilation in narrow, long terraces
9. Shallow foundations causing dropping of central spine wall
10. Damp basements

Question 4

Name 10 defects you would commonly find in a Victorian building.

Answer 4

1. Leaning chimneys
2. Overloading of roof due to change of materials (e.g. concrete tiles)
3. Removal of chimney breasts but not the stack
4. Damp penetration through solid walls
5. Rotting timber joists that are built into external wall
6. Wall tie failure (if a cavity wall, particularly in black ash mortar)
7. Differential settlement of bay windows (little to no foundations)
8. Rising damp caused by lack, failure or bridging of DPC
9. Blocked air vents to ground floors, causing dry rot
10. Lead water pipes

Question 5

Name 10 defects you would commonly find in a 1960s high-rise office block.

Answer 5

1. Flat roof problems
2. Parapet walls (loose copings)
3. Poor workmanship (inadequate re-bar cover)
4. Concrete defects - carbonation/chloride attack
5. Deleterious material - asbestos/HAC/brick slips
6. Cold bridges
7. Overloading of floors (filing cabinets)
8. Poor access and egress - narrow staircases, change in levels
9. Brittle metal windows
10. Corrosion of steel fixings

Question 6

What defects would you commonly find in a CLASP building?

Answer 6

1. Penetrating damp through failed joints
2. Poor gaskets around windows
3. Pitched fibre drainage deformed, collapsed or become blocked
4. Cold bridges
5. Excessive solar gain to some elevations
6. Poor U-values of the building fabric
7. Asbestos - boarding around steel members/ceiling tiles/pipe lagging/floor coverings etc
8. Rotting of timber floors and roofs in earlier Marks

Question 7

What typical defects would you find in a NZ building?

Answer 7

1. Water leaks due to poor weatherproofing
2. Cracks in walls and foundations
3. Issues with cladding systems like monolithic fiber-cement
4. Inadequate roof overhangs
5. Faulty window installations
6. Poorly sealed joints
7. Dampness from poor ventilation
8. Uneven floors
9. Problems with exterior finishes like peeling paint

Question 8

What are the factors contributing to defects in NZ buildings?

Answer 8

1. Climate: High levels of rain and wind can exacerbate issues with weatherproofing.
2. Building materials: Using inappropriate materials for the climate
3. Construction quality: Poor workmanship or lack of proper supervision
4. Design flaws: Inadequate detailing for weatherproofing or drainage

Question 9

What are the most common forms of cladding in NZ?

Answer 9

1. Timber or fibre-cement weatherboard
2. Brick veneer
3. Plaster

Question 10

What are typical defects of timber or fibre-cement weatherboard wall cladding?

Answer 10

1. Rot damage
2. Peeling paint and deteriorating stain finishes
3. Splits and cracks

Question 11

What are the typical defects of brick veneer wall cladding?

Answer 11

1. Cracking
2. Loose bricks
3. Missing mortar

Question 12

What are the typical defects of plaster wall cladding?

Answer 12

1. Cracked
2. Bulging/drummy
3. Peeling plaster
4. Lichen and moss build-up

Question 13

What are the types of foundations in NZ buildings?

Answer 13

1. Concrete slab-on ground
2. Pile
3. Ring and pile

Question 14

What are the typical defects of the foundations?

Answer 14

1. Borer and rot-damaged subfloor timbers
2. Rusted out pile to bearer fixings
3. Wet timber framing
4. Damp ground
5. Eroded or underminned foundations

Question 15

What joinery is the most common in NZ?

Answer 15

1. Timber
2. Aluminium
3. UPVC

Question 16

What are the defects in timber joinery?

Answer 16

1. Rot damage
2. Cracked putty
3. Peeling paint
4. Rusted hinges and flashings
5. Sticking or binding joinery
6. Gaps or warped joinery

Question 17

What are the defects in aluminium joinery?

Answer 17

1. Mitres that have opened up.
2. Worn friction stays
3. Deteriorated rubber seals
4. Broken hardware
5. Ill-fitting or inoperable joinery

Question 18

What is double glazing?

Answer 18

Two panes of glass are sealed in a unit (IGU) separated by a spacer bar. The space between the panes (usually 6-12mm) creates an air gap that slows down thermal transfer (hot or cold) by conduction – it doesn’t ‘trap heat’ but it slows down the movement of heat to reduce heat loss.

Question 19

What are some common problems with drainage systems?

Answer 19

1. Blockages
2. Cracked pipes
3. Leaking joints
4. Pipe specification

Drainage systems are constantly exposed to wear and tear that eventually causefractures to the pipes. These cracks are typically located near the joints where wastewater can leak through, flow into the lower, surrounding areas, and weaken their structure.
Clogging, poor design, and outdated infrastructure are just a few factors that contribute to faulty drainage systems.

Question 20

What is Leaky Building Syndrome?

Answer 20

A leaky building is one where moisture gets between the outside of the house (the cladding) and the inside walls. If there’s no way for the water to drain out because of a lack of drainage and ventilation between the cladding and the framework, the water becomes trapped. The walls can potentially rot and dangerous fungus can grow, causing structural problems for the building and health problems for those who live there.

Question 21

What is the time period for a Leaky Building?

Answer 21

Between 1988 and 2004.

Question 22

What contributed to Leaky Buildings?

Answer 22

1. Monolithic cladding (like plaster)
2. No cavity (plaster was fixed directly to the structure)
3. Bad design trends of the time (flat roofs and no eaves)
4. Untreated timber

In 1993, a new building code came into practice at the same time more homes were being built in a Mediterranean style.
This style of home had flat roofs, no eaves, and was built with plaster – rather than the tried-and-true brick facade.
The Leaky Homes crisis became very apparent in the early 2000s. And while measures were put in place to rectify the problem, Leaky Homes continue to be a problem today.

Question 23

What main style of building is leaky building syndrome?

Answer 23

1. Use plaster-style monolithic cladding. Exterior walls typically have an unbroken or smooth appearance.
2. Built in the mediterraen style.
3. Usually feature textured wall surfaces made out of plaster over polstyrene or fibre cement sheet.

Question 24

What are the Leaky Building risks?

Answer 24

1. Ground clearance: Not enough space between the cladding and the ground, paving or deck or insufficient slope away from the edge of the building. The clearance to solid ground (concrete, asphalt, paving or decking timber) should be 150mm. The clearance to soil should be 225mm.
2. Cracking in cladding: Look for hairline cracks in the cladding, typically found close to windows and doors, or discoloured cladding in these areas.
3. Joinery: Check for cracks along the joinery seals between the joinery and the cladding.
4. Penetrations or openings: Check all penetrations or openings in the cladding (for example, around pipes, vents or meter boxes) for gaps and lack of sealant. Also, check that meter boxes have appropriate flashing. Lack of flashing or reliance on sealant may allow water to penetrate.
5. Pergolas: If a pergola frame penetrates or is directly fixed through the cladding, water may be able to seep inside.
6. Windows: Check window flashings (thin pieces of waterproof material that direct water out and down, rather than into a building). Round or corner windows are difficult to flash, increasing the risk of water getting in.
7. Enclosed balcony/cantilever deck: These can present a multitude of risks:
   - A lack of slope on the balustrade.
   - Hand railings attached through the plaster cladding.
   - Poorly applied waterproof membrane.
   - Insufficient drainage holes allowing water to pool after rain.
   - Lack of clearance between the cladding and deck floor.

Question 25

What did the Government do to ‘fix’ Leaky Homes?

Answer 25

The Building Act was amended in 2004.
For starters, cavities (a gap between the interior and exterior) were reintroduced to allow water to drain away from the house frame.
Flat roofs and eaves dissolved as a trend, and major changes were made to the building code.

Question 26

How do you remediate Leaky Homes?

Answer 26

Some homes are so water-logged and rotten that they would have to be bulldozed.
Some proeprties can be fixed but it is expensive.
Options:
1. In situ timber treatment
2. Targeted repair
3. Partial reclad
4. Full reclad

Question 27

What is cold bridging?

Answer 27

• Cold bridging occurs in localised spots where the nature of the construction allows heat to escape through the structure at a higher rate than normal
• This creates situations where there may be quite low internal surface temperatures which can encourage patches of local condensation

Question 28

What is the guidance on Leaky Homes?

Answer 28

Department of Building and Housing - Weathertightness: Guide to the Diagnosis of Leaky Buildings

Question 29

Where would you expect to find cold bridging?

Answer 29

1. Concrete lintels crossing cavity walls
2. Uninsulated box-section lintels
3. Jambs and sills with returned blockwork inner leaf
4. Floor slabs lacking insulated upstands

Question 30

What is radon and why is it a problem?

Answer 30

1. Natural radioactive gas that cannot be seen, smelt, heard or felt
2. Emanates from minute amounts of uranium that occur naturally in all rocks and soils
3. Most radon disperses harmlessly into the air outside but some will collect in spaces under or within buildings
4. Exposure to high levels of radon can increase the risk of developing lung cancer

Question 31

In which areas of the UK are you most likely to come across radon?

Answer 31

Some parts of the country (e.g. the West Country, Derbyshire and Northamptonshire) have higher levels than elsewhere

Question 32

Other than radon, what other ground gases are problematic and why?

Answer 32

1. Methane - explosive in air at concentrations between 5-15%, generated by the anaerobic (absence of oxygen) degradation of organic material
2. Carbon dioxide - dlassed as highly toxic - can result in headaches and shortness of breath

Question 33

Name some legislation that detail requirements when considering ground gases.

Answer 33

1. Town and Country Planning Act 1990 - potential for contamination and risk from landfill and ground gases must be considered during development
2. Environmental Protection Act 1990 - where potential for significant harm exists to a development (either existing or proposed), the local authority can enforce appropriate remediation or mitigation
3. Building Regulations Approved Document C - where there is a potential risk, further investigation is required to determine whether gas measures are required and what level of protection is necessary

Question 34

How would you find out whether radon gas was a problem in a particular area?

Answer 34

1. Desk-based study of the history and geology of the area and any additional information such as mining or landfill activities
2. Public Health England (formerly the Health Protection Agency) and the British Geological Survey publishes maps of radon affected areas across and sets threshold levels for both commercial and residential properties
3. Maps can also be found in BRE Report BR 211 (Radon)

Question 35

What steps would you need to take if your client wanted to build in an area where radon gas was present?

Answer 35

Passive (basic protection):

• Usually achieved by increasing the airtightness of the DPM and extending it across the external leaf of brickwork
• Can also improve ventilation under suspended timber and concrete floors by installing airbricks

Active:

• Used where risks are higher
• Sump pumps connected to a fan in order to extract
• May be required if protective membrane is damaged

Alarm Systems:

• Designed to trigger when gas concentration reach a certain level

Question 36

What is Japanese Knotweed and when was it introduced?

Answer 36

• A hardy bamboo-like plant that grows quickly and strongly
• Introduced to the UK in the mid-19th Century

Question 37

What legislative controls exist for Japanese Knotweed?

Answer 37

1. Banned in the Wildlife and Countryside Act 1981, making it an offence to plant or cause the growth of Japanese Knotweed
2. The Environmental Protection Act 1990 also contains a number of legal provisions, designating contaminated soil as controlled waste, meaning only properly licensed organisations can remove it

Question 38

What problems are associated with Japanese Knotweed?

Answer 38

• Japanese Knotweed is extremely invasive and can cause serious damage to:
  
  • Drains and buried services - can exploit cracks and gaps in pipework
  • Patios, paths and drives - can grow between joints
  • Boundary and retaining walls - can undermine walls with shallow foundations
  • Outbuildings - can overwhelm lightweight structures (sheds, garages etc.)
• There are claims that damage to building foundations can also occur, however this is rare
• The plant can remain dormant, so eradication may be difficult to guarantee

Question 39

How would you identify Japanese Knotweed?

Answer 39

RICS Information Paper ‘Japanese Knotweed’ - Appendix C contains an identification chart throughout the seasons, namely:

1. Hollow stems within distinct raised nodes (like bamboo) which develop purple speckles
2. Can reach heights up to 3-4m in its growing season (summer) and grow in dense clumps (aka ‘stands’)
3. Leaves are lush green and flat heart/shield shaped, approx. 70-140mm long and 50-120mm wide
4. Flowers are small, creamy white spikes of length approx. 60-150mm

Question 40

How would you remediate the problems caused by Japanese Knotweed?

Answer 40

Specialist contractor required, who may specify:

1. Excavation/removal of plant and roots - can extend 3m down and 7m across
2. Biological control - use of ‘pests’ that attack and control the plant
3. Chemical control - use of specialist herbicides (can take up to 3 years to completely eradicate)
4. On-site burial - may require a specialist root barrier membrane

Question 41

What is Giant Hogweed and when was it introduced?

Answer 41

Introduced as an ornamental plant in the 1890s

Question 42

What legislative controls exist for Giant Hogweed?

Answer 42

Banned in the Wildlife and Countryside Act 1981, making it an offence to plant or cause the growth of Giant Hogweed

Question 43

What are the problems with Giant Hogweed?

Answer 43

1. Contact with its sap (present inside the stem and on the hairs that cover the leaves and stem) makes skin highly sensitive to ultra-violet light
2. No discomfort is experienced until around 15-20 hours after exposure, where burns develop that quickly turn into large watery blisters, which recede and leave scars that remain highly photosensitive for years or even life
3. Can cause blindness if contact is made with the eyes
4. Suggestion that toxins within the sap are carcinogenic and could cause cancer or result in malformations of unborn foetuses in pregnant women

Question 44

How would you identify Giant Hogweed?

Answer 44

1. Often grows between 3-5m over four years
2. Stems - hollow, purple (or green speckled with purple) and covered in fine hairs
3. Leaves - dark green, coarsely toothed, hairy like stems, measuring up to 2m across
4. Flowers - numerous small and white flowers, emerge in mid to late summer on top of the stems in umbrella-like clusters

Question 45

How would you remediate the problems caused by Giant Hogweed?

Answer 45

Specialist contractor required, who may specify:

1. Herbicidal treatment - effective, but must be undertaken regularly over several years (seeds can remain dormant for up to 7 years)
2. Dig up and dispose as controlled waste (may need to excavate up to 4m around plants due to seed spread)
3. Combination of both

Question 46

What should you do if you come into contact with Giant Hogweed?

Answer 46

1. Wash immediately with soapy water any area of skin that comes into contact
2. If contact is made with the eyes, flush immediately with water
3. Cover affected areas and keep out of sunlight for at least 48 hours
4. Seek medical advice

Question 47

What is Regent Street Disease and how is it caused?

Answer 47

1. Also known as steel frame corrosion
2. Affects buildings constructed circa 1905 onwards (i.e. when steel became a popular construction material)
3. Load-bearing frames of steel were clad with stone, brickwork or terracotta (notched around the steel frame) with the voids between the two filled with low grade mortar
4. Mortar compaction was poor and often contained lumps of brick or stone, which increased the number of voids
5. Inevitable shrinkage cracks meant that water and oxygen could penetrate the fabric, facilitating corrosion of the steel

Question 48

What problems are associated with Regent Street Disease?

Answer 48

1. Corroded steel expands at least four times its original volume
2. Due to the infilled voids around the steel, expansion inevitably results in cracking of façade, allowing more water to penetrate
3. In extreme cases, loss of support can result from horizontal cracking, causing collapse of pieces of stone or brick

Question 49

How would you identify Regent Street Disease?

Answer 49

1. Vertical or horizontal cracking reflecting the location of the steel frame
2. Physically opening up the façade is an option, although disruptive and may require consent if listed
3. NDT (non-destructive testing) systems are also available to determine the extent of the corrosion or prognosis for future deterioration

Question 50

What steps would you recommend to remediate Regent Street Disease?

Answer 50

1. Expose, clean and protect the steel - expensive and disruptive
2. Provide a corrosion barrier to the steel and then create a void around it so if further corrosion does occur, it will not result in cracking
3. Cathodic Protection Systems

Question 51

Is Regent Street Disease in New Zealand?

Answer 51

No, “Regent Street Disease” is not typically found in New Zealand as it refers to a specific type of building deterioration affecting mainly older buildings in the UK, particularly those on London’s Regent Street, due to corroding steel frames within masonry facades; while similar issues with old buildings might exist in New Zealand, the term “Regent Street Disease” is not commonly used there as the problem is not as prevalent in the same architectural style and climate conditions.

Question 52

Give an example of an interesting pathology issue you have had to deal with?

Question 53

What are the common causes of spalled brickwork?

Answer 53

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Question 54

What is frost action?

Answer 54

1. Caused by a combination of excessive wet brickwork and freezing temperatures
2. When water turns to ice, it expands
3. The repeated freeze-thaw cycle produces stresses on the brick causing it to spall (the face flaking/crumbling off)

Question 55

Why may the use of strong mortars exacerbate the problem of frost action?

Answer 55

Strong mortar tends to suffer from shrinkage cracks which will allow water to penetrate, and because strong mortars are not as ‘breathable’, it will be difficult for the water to evaporate

Question 56

A white powdery substance has appeared on the surface of some new brickwork. What might it be and what can you do about it?

Answer 56

Efflorescence:

• May only be problematic in cases of rising damp, as the crystals can sometimes block pores in brickwork, thus preventing evaporation and driving damp higher up the wall
• Can be brushed off if appearance is causing a concern

Question 57

You notice the gable wall of an end terrace property is bowing - what could be the reason for this?

Answer 57

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Question 58

What is ‘bookend effect’ and how is it caused?

Answer 58

1. Bulging of a flank wall due to lack of lateral restraint, often due to floor joists running parallel with the wall and/or lack of buttresses
2. Common in buildings built before the mid-1980s however can occur later if alteration are undertaken (e.g. removing a chimney breast that was previously acting as a buttress, removing an internal perpendicular wall or even creating an opening in such a wall)
3. Problem often accentuated by the presence of the staircase adjacent to the flank wall

Question 59

How can ‘bookend effect’ be remediated?

Answer 59

Remedial works involves mechanical insertion of metal tie rods along the length of wall

Question 60

What problems are likely to be associated by rendering over external brickwork?

Answer 60

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Question 61

What issues may there be with a partial fill cavity wall in respect of workmanship?

Answer 61

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Question 62

What is snapped header defect and how is it caused?

Answer 62

1. Often used to save money (facing bricks were much more expensive than commons and therefore ‘snapping’ the brick in two could provide two facing brick heads)
2. Header bricks were traditionally used to tie solid walls together
3. Snapped headers cause defects as there is a lack of tying-in between the inner and outer face

Question 63

How can you tell when timber structural members are deflected or bowed?

Answer 63

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Question 64

A hall floor is re-laid but the screed fails - what are the possible reasons for this?

Answer 64

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Question 65

How can stonework be repaired?

Answer 65

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Question 66

What causes rainwater goods to become defective?

Answer 66

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Question 67

How would you determine if a drainage run was free from and breaks or blockages?

Answer 67

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Question 68

What action might be necessary to free up sliding sash windows that are sticking?

Answer 68

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Question 69

What defects would you associate with portal framed warehouse units?

Answer 69

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Question 70

What is cut edge corrosion?

Answer 70

Occurs when the protective coating on metal sheeting peels back at lap joints (usually where it has been cut), exposing the base metal to risk of corrosion, which can cause section loss

Question 71

How do you repair cut edge corrosion?

Answer 71

1. Remedial work involves cleaning the effective area, removing the defective coating (e.g. by chemical stripping) and treating the sheet lap with a silicone based paint
2. Current guidance states cut edges should be painted before installation, however this is often neglected

Question 72

What problems can arise from using two different metals next to each other?

Answer 72

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Question 73

What are protected species in the UK?

Answer 73

1. Bats
2. Newts
3. Toads
4. Frogs
5. Snakes
6. Lizards
7. Butterflies
8. Otters
9. Badgers
10. Breeding birds
11. Dormice

Question 74

What are the protected species in New Zealand?

Answer 74

1. Native lizards and frogs
2. All marine mammals
3. Seabirds (except black-backed gulls)
4. Waterfowl

Construction projects that may affect protected species require a Wildlife Act Authorisation from the Department of Conservation (DOC).

Wildlife Act 1953

Question 75

What is Sick Building Syndrome (SBS) and what are the ‘symptoms’?

Answer 75

Sick building syndrome (SBS) refers to a condition where people experience various non-specific symptoms like headaches, eye irritation, fatigue, and throat discomfort while occupying a particular building, with the symptoms typically improving when they leave the building, and where no specific identifiable cause of illness can be found

Question 76

What are the causes of Sick Building Syndrome?

Answer 76

No single cause is definitively identified, but factors like poor ventilation, high levels of carbon dioxide, chemical emissions from building materials, mold growth, dust mites, and improper building maintenance can contribute.

Question 77

What is the diagnosis and management of Sick Building Syndrome?

Answer 77

Diagnosis:
Diagnosis is based on the pattern of symptoms experienced by multiple occupants within a building, which improve when leaving the building, and by ruling out other potential medical causes.
Management:
Addressing the underlying issues with building ventilation, cleaning practices, and identifying and removing potential contaminants are key to managing SBS.

Question 78

What was the Grenfell Tower Fire? When was it?

Answer 78

on 14th June 2017, a high-rise fire broke out on the 24-storey block of flats in North Kensington, West London. It burned for 60 hours. Seventy people dies at the scene and two dies later in hospital.

Question 79

What was the cause of the Grenfell Tower fire?

Answer 79

The Grenfell Tower fire was caused by an electrical fault in a refrigerator that ignited flammable materials and spread rapidly through the building. The fire was fueled by combustible cladding panels on the outside of the building.

The yearslong public inquiry into the 2017 blaze found that there was no “single cause” of the tragedy, but said a combination of dishonest companies, weak or incompetent regulators and complacent government led the building to be covered in combustible cladding that turned a small apartment fire into the deadliest.