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RICS APC - Residential (TS NBS) > Building Pathology Level 3 > Flashcards

Building Pathology Level 3 Flashcards

1
Q

When was the Georgian period?

A

1714 - 1830

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2
Q

Typical Georgian foundation defects?

A
  • Small thickness
  • Minimal drainage
  • Heave/subsidence
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3
Q

Typical wall defects Georgian

A
  • Bricks - deterioration
  • Rotten sash windows
  • Repainting/Repointing issues
  • Bowed brick walls
  • Structural failure - Lack of lateral restraint
  • Bay window roof problems
  • Damp basements
  • Load-bearing timber partitions
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4
Q

Georgian - causes of damp

A 
Cracking, spalling brickwork 
Condensation 
Interstitial Condensation 
Penetrating damp 
Bridging DPC 
Blocked air vents
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5
Q

Georgian - floor defects

A

Springy floor - decaying timber joists

Deflecting timbers

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6
Q

Georgian - roof defects

A

Leaks from roof

Roof structure defects

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7
Q

What is the Victorian period?

A

1830 - 1900

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8
Q

Victorian - foundation defects

A
  • Subsidence (trees and drains)
  • Differential movement (e.g where basements are present for part of the footprint)
  • Bays (shallow footings)
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9
Q

Victorian - wall defects

A
  • Book end effects
  • Blocked air vents
  • Removal of chimney breast
  • Blown render
  • Party walls unbonded to external wall (movement)
  • Failing brick arch
  • Wall tie failure
  • Cement mortar used instead of lime mortar
  • Water ingress
  • Condensation
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10
Q

Victorian - floor defects

A

Rot - in timber beams
Water ingress - through corbels
Lack of ventilation

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11
Q

Victorian - Roof defects

A 
Roof coverings (nail sickness, defective slates) 
Re-roofing - concrete tiles
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12
Q

Victorian - services defects

A
  • Lead pipes

- Chimneys - use of chimney as gas appliance flue without liner

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13
Q

Victorian - How does damp occur?

A
  • Penetrating - (RWG, splashback, flashings, chimney stack)
  • Condensation
  • Plumbing leak
  • Salt contamination
  • Rising damp
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14
Q

Mid-war houses - foundation depth

A

900mm for clay soil

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15
Q

Victorian - foundation depth

A

PROVIDE ANSWER

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16
Q

Post war housing - floor defects

A

Sulphate reaction of hardcore - expands and lifts slab

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17
Q

Types of non-trad housing

A

steel framed​

timber framed​

precast reinforced concrete construction​

cast in-situ concrete construction

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18
Q

Steel framed systems

A
  • designated as defective under the Housing Defects Act 1984
  • primary concern is the potential for corrosion of the frame
  • BISF
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19
Q

Timber frame (non -trad)

A

Defects are typically related to moisture and consequent timber decay.
Condensation also poses a risk

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20
Q

Cast in-situ concrete construction

A

Cast in-situ concrete systems were poured on-site into a timber ‘formwork’ called shuttering.
Can suffer corrosion
EXAMPLE

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21
Q

Precast reinforced concrete construction

A

Precast reinforced concrete systems were manufactured off-site, and ‘slotted together’ on-site
The primary concern in houses of concrete construction is carbonisation of the concrete, which can result in the reinforcing steels rusting, compromising the building’s structural integrity.
EXAMPLE

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22
Q

What is the Housing Defects Act 1984?

A
  • introduced compensation for home-owners who had bought homes from local authorities
  • a scheme of licensed repair grants offered to owners whose homes were identified as ‘Designated Defective
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23
Q

Non-trad defects

A

The main problem with non-traditional houses is the decay of the reinforcement bars in the walls

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24
Q

LPS

A

Large panel system (LPS) structures are like a ‘house of cards’ made of concrete panels. Floors and walls rest one upon the other, held together only by their own weight, until a lateral force is applied.

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25
Q

Cross wall

A
  • a new design of houses was introduced which pared down the structural frame to just 2 walls.
  • These 2 walls formed the party walls between terraced or semi-detached houses, and carried all the main loads to the foundations.​
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26
Q

Issues with chimney stacks

A

Open flue​

  • Can lead to water ingress and vermin to enter (may cause blockages). ​
  • Pots that are not in use should have a rain guard or ventilated inserts.​

Closed flue​
- When flue sealed for disused flues must include internal vents to prevent damp issues.​

Mortar and tile flashing failure

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27
Q

Chimney breast removal

A

When chimney breast has been removed must be adequately supported.

  • Gallows brackets
  • A more secure alternative to brackets is a steel L-section beam that sits on the load-bearing walls of the house and supports the stack above.
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28
Q

What is capillary action?

A

Where liquids can travel – horizontally or vertically (against the force of gravity) in small spaces within materials

The movement is due to the surface tension that results when liquid or moisture is contained within very fine spaces or tubes

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29
Q

Chimney stack water ingress

A

Water ingress can occur via:​

  • Open pots​
  • Flashing failure​
  • Lack of DPCs in the stack
  • Sulphate attack in brickwork
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30
Q

Sulphate attack in chimney stacks

A

Burning fuels leads to hygroscopic salts (sulphates) building up in unlined chimneys.​

Water can help the salts/sulphates penetrate in the mortar. Reaction between sulphate and mortar can create crystals when it dries out in the mortar, expanding the joint width.

31
Q

Causes of timber rot

A

Poor maintenance ​

Defective rainwater goods​

No bell mouth drip to window cills​

Poor workmanship to roof e.g. tiles not overhanging into rainwater goods

32
Q

Flat roof defects

A

Asphalt blisters​

Asphalt cracking/crazing​

Chipboard deck failure

Condensation

33
Q

What is Interstitial condensation

A

occurs when the moist air vapour penetrates through the elements of a building’s fabric, experiencing a temperature difference along the way, and condensing not on the surface but within the building fabric itself.

34
Q

What are finlock gutters and common issues?

A

Concrete gutters
Worked well in closing top of cavity walls and served as a load bearing role for window and door openings.

Common issues for Finlock gutters​

  • Lining failure mainly due to thermal expansion and contraction​
  • Thermal/cold bridging.
  • Sagging-can occur if windows or doors underneath are poorly replaced.​
35
Q

Modern drainage system

A

All modern properties are built with a 2-type drainage system where rainwater and foul water are dealt with separately.

36
Q

BRE 251 digest - Category 1

A

Fine cracks 1mm - Damage generally restricted to internal wall finishes; cracks rarely visible in external brickwork.

37
Q

BRE 251 digest - Category - 2

A

Up to 5mm

Cracks not necessarily visible externally; some external repointing may be required to ensure weather-tightness.

38
Q

BRE 251 digest - Category - 3

A

5-15mm or several of 3mm

Cracks that require some opening up and can be patched by a mason.

Repointing of external brickwork and possibly a small around of brickwork to be replaced.

Weather-tightness often impaired.

39
Q

BRE 251 digest - Category - 4

A

15 - 25mm

Extensive damage which requires breaking-out and replacing sections of walls, especially over doors and windows.

Windows and door frames distorted, floor sloping noticeably.
Walls leaning or bulging noticeably, some loss of bearing in beams.

40
Q

BRE 251 digest - Category - 5

A

Greater than 25 mm

Structural damage that requires a major repair job, involving partial or complete rebuilding.

Beams lose bearing, walls lean badly and require shoring.
Windows broken with distortion.
Danger of instability.
Typical crack widths are greater than 25mm, but depends on number of cracks.

41
Q

What is roof spread caused by?

A

Lack of lateral restraint

42
Q

Three types of asbestos

A

crocidolite, commonly known as ‘blue’​

amosite, commonly known as ‘brown’; ​

chrysotile, commonly known as ‘white’.

43
Q

Japanese Knotweed

A

Hardy, bamboo like perennial plant (lives more than 2 years).

Can quickly grow to a height above 2m.​

Spreads through underground rhizomes or roots.

44
Q

Identification of Japanese Knotweed

A

March-April: Plant in early stage of life cycle and some visual characteristics will have not developed.​

May-October: Vigorous growth. Alternating leaves.​

October-February: Plant dies back (black canes)

45
Q

Japanese Knotweed treatment

A

1) Excavate plant and roots: ​
2) On-site burial and/or encapsulation with membranes: ​
3) Biological control: ​
4) Chemical control:​

46
Q

What is dry rot?

A

Dry rot requires roughly 20% moisture content in the timber to begin growing.
Spreads via mycelium
Signs of dry rot include:​
- damaged or decaying timber​
- damp or musty smell​
- Cuboidal cracking
- concentrated patches of orange–brown spore dust​
- grey strands on timber​
- fruiting bodies that look like large mushrooms.

47
Q

Dry Rot - Treatment

A 
Chemical treatment
Holistic approach (manage dampness more effectively in the building)
48
Q

Wet Rot

A

Wet rot will begin to grow when the moisture content of the timber or other permeable surface reaches around 50%

Common signs of wet rot​

  • Damp of must smell ​
  • cracking timber​
  • softened or spongy timber​
  • discoloured or distorted timber​
  • weakened timber​
  • black–brown fungal growths.
49
Q

Wet rot treatment

A

First step is to determine the cause of the outbreak (finding and eliminating the source of dampness).​

Weakened timber must be replaced but common to remove and replace all infected timber.​

Where moisture source cannot be eliminated can be replaced with pre-treated timber or materials that cannot rot e.g. concrete or steel.​

Treat surrounding timber and masonry with fungicides.

50
Q

What is Common furniture beetle

A

Woodworm is the wood-eating larva of many species of beetle​

Timber with moisture content of 16-18% provide conditions for wood boring beetle attack.​

If left untreated can weaken timber and lead to structural failure.​

Treatments include chemical insecticide and replacing badly damaged timber.

51
Q

Death watch beetle

A

Rounded tunnels with boreholes of around 2 mm in width. ​

Tunnels are filled extensively with frass, which is clearly visible upon inspection. ​

Creates a distinctive tapping sound to attract mates – often on quiet summer nights.​

Prefers hardwood e.g. oak

52
Q

Four stages of defects

A

1) Inspection
2) Diagnosis
3) Prognosis
4) Remedy

53
Q

What are deleterious materials?

A

Materials that are prohibited for use in a project.

- Calcium silicate brickwork

54
Q

Rising damp

A

Rising damp is a form of damp that affects the walls of buildings. ​

Occurs when moisture from the ground travels up through the walls by capillary action (ground water is sucked up through tiny tubes in the bricks).​

This water contains salts that also travel up through the wall. These salts are then deposited on the surface of the wall. Deposits of salts are hygroscopic and attract/absorb moisture/water vapour in the house.​

Mainly caused by an absence of a DPC or a defective DPC but can also be caused by a bridging of the DPC.​

DPC bridging is a construction fault that allows damp from the ground to travel up past the DPC.​

Internal or external renders overlapping the DPC, external ground levels above the DPC, cavity wall insulation etc.

55
Q

Condensation

A

Occurs when moist air comes into contact with cooler surfaces that are at or below the dew point e.g. windows, single skin walls etc.​

High internal moisture levels, cold surfaces and a lack of ventilation are contributory factors to condensation and mould.​

Must consider this when differentiating between penetrating damp and condensation.​

Condensation staining patterns are frequently more apparent towards the junctions of walls, floors and ceilings, with the greatest focus in corners. ​

Gives rise to the characteristic crescent shaped formation, shown here with severe black mould growth.

56
Q

Penetrating damp

A

Penetrating damp is the result of water infiltration through an external wall and into the property. ​

Occurs either due to water entering through a defect in the building or when external brick or stone walls have degraded to the point where they become porous and allow water ingress to pass through the external wall into the property.​

Causes:​

Different types of building defects - including overflowing gutters, leaking or blocked pipes, damaged pointing and flashing, dilapidated or poorly installed windows and missing roof tiles.​

Porous walls – ageing bricks lose their ability to keep out rain penetration while cracks in external render allow problematic water ingress.​

Spalled bricks and degraded mortar – damage to brickwork can allow water to penetrate into your home.​

57
Q

What is subsidence?

A
  • the downward movement of the ground unconnected with the weight of a building and will occur whether there is a building or not
  • Ground failure i.e outside influence on the ground
  • Trees and drains cause 90% of subsidence cases

The building is damaged by a failure in the ground

58
Q

What is settlement?

A

the downward movement of the site on which the building stands, due to the application of the superimposed load (weight) from the building

Compressing of the ground by the weight of the building

Failure to the fabric of the components of the building

59
Q

Heave

A

The upward movement of the site, normally due to expansion of a previously desiccated or shrunken clay as it rehydrates

60
Q

What is roof spread?

A

Roof spread is caused when the weight of the roof produces a horizontal outward force at the top of the walls (triangle wants to flatten).
The tops of the walls can be visibly displaced and cracks appear at the junctions between the external walls and internal partitions/ceilings
Remedial works generally involve the installation of collar beams to tie between the rafters thus resisting the outward forces

61
Q

Cavity wall tie failure

A

In older properties where the outside wall is not watertight the galvanised steel ties can rust. When they rust they swell and this creates horizontal cracks in the mortar. Other common signs can be bulging brickwork or movement of the lintels.

62
Q

concrete decay

A

Carbonisation, Alkaie Silica reaction, sulphate attack, chloride attack, High alumina cement - MORE WORK NEEDED HERE

63
Q

Legionella

A
64
Q

Brick dimensions

A

215 x 102.5 x 65 mm

65
Q

Nail sickness

A

Nail sickness occurs when metal nails that secure the slates in position corrode to such an extent that the weight of the slate breaks through the corrosion, allowing the slate to slip

66
Q

Inherent defect

A

Defect in material or design

67
Q

Latent defect

A

Discoverable - more info needed

68
Q

Types of testing

A

Boroscopes, damp meter, pressure test, use of dyes

69
Q

Removal of chimney breasts

A

When chimney breast has been removed must be adequately supported. ​

Gallows brackets can be used to support remaining stack (steel brackets bolted to the wall).​

A more secure alternative to brackets is a steel L-section beam that sits on the load-bearing walls of the house and supports the stack above.

70
Q

Chimney stacks where can water ingress occur

A

Open pots​

Flashing failure​

Lack of DPCs in the stack

Sulphate attack in brickwork

71
Q

Defective chimney stacks - Sulphate attack

A

Burning fuels leads to hydroscopic salts (sulphates) building up in unlined chimneys.​

Water can help the salts/sulphates penetrate in the mortar. Reaction between sulphate and mortar can create crystals when it dries out in the mortar, expanding the joint width.​

Mortar/joints facing the prevailing winds are less affected as they dry faster. Side of chimney breast that dries slowest will allow more crystals to form and expand more on this side. ​

However, the joints facing the prevailing winds weather faster (mortar weakened by sulphate) resulting in the bricks settling. ​

This results in the stack often leaning into the prevailing wind.​

Prevailing winds usually West/South West

72
Q

Underpinning ​

A

Underpinning ​

Mass concrete underpinning​

The most common method is traditional mass concrete underpinning - a simple technique that involves excavating a segment of ground below the existing building foundation in controlled stages, to a depth where suitable bearing strata exists.​

The excavation is then filled with concrete and allowed to cure before the next ‘pin’ is excavated. To transfer the building load safely to the new pin, a dry sand cement packing mortar is rammed in between the new and old foundation.​

This method is low cost and suitable for shallow depth underpinning. Work can be carried out from one side of the wall and in areas of difficult and restricted access. It is suitable for heavy foundation loads and massive structures and for the formation of new cellars and basements beneath existing buildings.​

In years gone by contractors tended to be paid on how much concrete they laid, rather than laying the right amount, so a great deal of concrete was poured. ​

Also, the use of partial underpinning seems to be a problem, this adds a great deal of weight to one part of the building, making it a lot more rigid than the part that is not underpinned. The two parts of the building are therefore going to act differently.​

As a result modern methods to repair structural movement include helical wall tie bars or micro-pile systems.​

73
Q

Japanese knotweed damage categories

A

4​)
Japanese Knotweed is within 7m of habitable space, conservatory or garage (can be in or outside boundary of subject property).​
Japanese Knotweed is causing serious damage to outbuildings, drains, paths etc.​
Further investigations by qualified person required.​
3​)
Japanese Knotweed present in properties boundaries but more than 7m from habitable space. Only minor damage to outbuildings, paths etc.​
Further investigations by qualified person required.​
2)​
Japanese Knotweed seen on neighbouring properties/land. Was within 7m of subject properties boundary but over 7m away from habitable space of subject property.​
1)​
Japanese Knotweed seen on neighbouring properties/land but over 7m from subjects boundary.​

74
Q

High alumina cement concrete

A

Differs from Portland cement, being composed calcium aluminates rather than calcium silicates.​

Its rapid strength development made HAC popular from 1950 to 1970. ​

Mostly used in precast beams​

1976 HAC concrete was banned for structural use in the UK​

Mineralogical ´conversion´ sometimes caused reductions in concrete strength and increased vulnerability to chemical attack. Loses structural strength.​

If the presence of HAC is suspected, confirmation requires chemical or laboratory testing of samples. If the presence of HAC is confirmed, professional advice on its condition may be required.

RICS APC - Residential (TS NBS) (18 decks)

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