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APC Building Surveying > Building Pathology > Flashcards

Building Pathology Flashcards

1
Q

What his HAC (high alumina cement) and what are the issues with it? How would you identify issues? What remedies are there?

A

Typically found in maritime application, HAC contains calcium aluminates and develops strength rapidly.

Typically used during the 1970s for strutural concrete.

HAC undergoes a mineralogical change called ‘conversion’ which increases its porosity and susceptibility to chemical attack.

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2
Q

What typical defects are found in Victorian era buildings?

A

Differential settlement.

Lack of lateral support between terraced houses.

External development raising the pavement level blocking air vents and breaching DPC.

Nail Sickness

Sagging Roof Timbers from replacement of slate tiles with heavier modern roof tiles.

Lead materials.

Timber decay.

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3
Q

What are typical defects associated with industrial buildings?

A

Cut-Edge Corrosion

Delaminating Plastisol

Fixings missing/damaged.

Leaking gutters.

UV damage to roof lights

Cracking/Impact Damage.

Asbestos

Carbonation

Cracked floor slabs

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4
Q

What is wet rot. How is it identified and how is it treated?

A

Wet rot is typically found where the moisture content is 50% or higher, and the timber has become spongy.

Treatment includes eliminating the source of moisture, drying the timber, removing the affected timber 500mm beyond the affected areas.

Treat the remaining timber and replace with new pre-treated timber.

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5
Q

What is dry rot? How is it identified and how is it treated?

A

Dry rot is typically found where the moisture content is between 20 - 50%. The timber will be brittle and have cuboidal cracking.

Treatment includes eliminating the source of moisture, drying the timber, removing the affected timber 500mm beyond the affected areas.

Treat the remaining timber and any adjoining areas and install pre-treated timber.

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6
Q

How do you identify woodworm?

A

Timber affected by woodworm will typically have many small flight holes from burrowing insects.

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7
Q

What is the lifecycle of woodworm?

A

Eggs are laid in cracks/splits.

Larvae hatch and then burrow into the wood.

Adult insects emerge and bore out of the timber.

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8
Q

What are the life stages of fungal attack?

A

Spores germinate.

Hyphae establish.

Mycelium form.

Fruiting bodies may form if conditions are favourable.

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9
Q

What defects are associated with GRP rooflights?

A

Loss of transparency due to UV degradation.

Failed seals/foam fillers.

Missing/failed fixings.

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10
Q

How does plastisol coating deteriorate?

A

Loses colour.

Caulks.

Delaminates.

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11
Q

What are typical roof coverings for a flat roof?

A

Rubber

Felt

Asphalt

Liquid Applied

Metal Sheets

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12
Q

What is cut-edge corrosion and how is it treated?

A

Cut-Edge corrosion is caused by the exposed ‘cut’ edge being unprotected from corrosion by moisture.

It will cause deterioration of the protective coating and corrosion to the roof sheet.

Can be cleaned and repaired with a coating system if not corroded beyond the fixings.

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13
Q

What is the minimum fall required on a roof?

A

The Building Regulations state 1:40 while British Standards state 1:80.

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14
Q

What are some common defects associated with flat roofs?

A

Incorrect falls.

Deflection.

UV Degradation.

Blistering

Crazing

Ponding

Cracks - Caused by thermal movement.

Impact damage

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15
Q

What is Carbonation and how is it treated?

A

Carbonation occurs when the alkaline elements of the concrete react with carbon dioxide. This creates calcium carbonate and lowers the PH level of the concrete.

The lower PH level reduces the passivity of the concrete and cause corrosion of the steel reinforcement.

To test, take out a section of the concrete and treat with Phenolphthalein, which will turn pink if the concrete is not carbonated.

To remedy, the affected concrete will need to be removed, the corrosion cleaned from the re-bar and the bar primed and a repair mortar used. An anti-carbonation coating can also be applied.

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16
Q

What is Sulphate attack and how can you treat it?

A

Sulphate attack occurs where sulphates in solution come into contact with concrete which cause a chemical reaction which causes concrete to expand and crack.

The concrete will need breaking out and replacing if badly damaged or a chemical admixture used to neutralise the reaction.

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17
Q

How do you identify Japanese Knotweed?

A

Green, shield shaped leaves.

Hollow bamboo-like stem, light green and speckled red.

Small, clustered creamy white flowers.

Thick and extensive Rhizomes.

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18
Q

What are the issues with Japanese Knotweed?

A

Rhizomes can enter cracks and exploit structural weaknesses.

Rhizomes can block underground services such as drainage or water pipes.

Mortgage providers can be wary.

Reduces land value.

Can spread easily,

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19
Q

How do you remedy Japanese Knotweed?

A

Excavation and disposal to a licenced waste management facility.

On-site burial.

Chemical control.

Biological Control through the introduction of pests that attack the JK.

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20
Q

What legislation controls Japanese Knotweed?

A

Wildlife and Countryside Act 1981

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21
Q

What are common types of damp?

A

Condensation

Rising Damp

Penetrating Damp

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22
Q

What is rising damp and how is it remedied?

A

Rising damp occurs with water being drawn up through capillary action from wet ground.

It can be detected by horizontal tide markings and deterioration to decorative finishes.

It can be cause by a bridged or non-existent DPC.

Remedies include installation of a DPC and increasing ventilation and heating internally.

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23
Q

What is penetrating damp and how is it remedied?

A

Penetrating damp occurs where water penetrates the building’s envelope.

This can be caused by saturation of walls due to prevailing winds, masonry defects, roof defects at the eaves, leaking rainwater goods, missing cavity trays or failed roof coverings.

The remedy is to find the source of the moisture, undertake appropriate repair them drying through heating and ventilation.

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24
Q

What is condensation?

A

The process of water vapour cooling and becoming liquid.

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25
Q

What is interstitial condensation?

A

Condensation that occurs within the structure of a building, typically at interfaces between materials. It tends to be hidden by construction and surface finishes.

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26
Q

How is condensation treated?

A

Improving heating, ventilation or insulation and removing sources of excess moisture such as drying laundry, cooking and showers.

Interstitial condensation may be resolved by improving insulation or changing a building detail if an inherent defect.

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27
Q

What are the three types of asbestos?

A

Chrysotile - White

Amosite - Brown

Crocidolite - Blue

28
Q

What can cause spalling masonry?

A

Incorrect application of pointing or non-breathable mortar.

Freeze-Thaw

Salt Crystallisation.

29
Q

What are the pros and cons of a warm roof?

A

A warm roof reduces the chance of thermal bridging, doesn’t require ventilation and reduces the risk of interstitial condensation.

The roof build up will be deeper however and is susceptible to compression under loads.

30
Q

What is the difference between a warm and a cold roof?

A

A warm roof has insulation laid on the substrate, whilst a cold roof has insulation laid between or below the substrate.

31
Q

What are the pros and cons of a cold roof?

A

A cold roof has a shallower build-up and can bear a more sizeable load.

However, it is more susceptible to thermal bridging and needs to be venilated to prevent damp.

32
Q

If you identify movement in a building, what further investigations may you consider?

A

Trees in close proximity

Neighbouring Dwellings

Engineers Survey

Drainage Survey

33
Q

What is heave, subsidence and settlement?

A

Heave occurs where the ground moves upwards due to soil expanding, for example because of drainage damage or tree removal.

Subsidence occurs where the ground sinks, bringing down the property’s foundations, for example where soils are rich in clay, trees are planted or the ground is unstable.

Settlement occurs where soil moves downwards due to the weight of newly built structures.

34
Q

How do you identify cracking causes?

A

Subsidence cracking usually occurs with cracks wider at the top than bottom, and diagonal running through masonry and blockwork.

Heave cracking usually occurs with wider cracks at the bottom than at the top.

35
Q

How do you rectify subsidence?

A

Underpinning the foundations, removing trees/vegatation and repairing any damaged pipework.

36
Q

What are the visual indicators of concrete carbonation?

A

The concrete around the reinforcement spalls and cracks, and the reinforcement will become exposed and corroded.

37
Q

What are the dimensions of a brick?

A

215 x 102.5 x 65mm

38
Q

What are the dimensions of a block?

A

440 x 215 x 100mm

39
Q

What factors may cause one to suspect carbonation?

A

Visual Inspection - Spalling and Corrosion.

Location - eg. in car park high levels of CO2 and other pollutants, as well as grit/salts.

Lack of cover to the concrete/exposed to rainfall.

40
Q

Name three common hazardous materials

A

Lead, Asbestos, and Urea Formaldehyde Foam

41
Q

Where is lead commonly found in buildings?

A

In lead pipes, lead based paints and in solder used to seal pipe joints

42
Q

Why is lead hazardous to health?

A

If ingested, lead can cause lead poisoning, which is potentially fatal.

43
Q

Where is Urea Formaldehyde Foam commonly found in buildings?

A

In cavity wall insulation.

44
Q

Why is Urea Formaldehyde Foam hazardous to health?

A

There is some evidence that it is carcinogenic, although this is not definitively proven

45
Q

Where can Asbestos commonly be found in buildings?

A

Asbestos can be found in a variety of materials used in building construction including sheet cladding panels, insulation, boarding, adhesive, artex decorative finishes and pipe lagging.

46
Q

Why is Asbestos hazardous to health?

A

Asbestos fibres, when disturbed, can be inhaled and cause multiple health issues including Asbestosis and Lung Cancer. Long term exposure can be fatal.

47
Q

What is the main piece of legislation controlling Asbestos and when was Asbestos use banned?

A

Asbestos was fully banned in the UK in 1999, when Chrysotile was banned. Crocidolite and Amosite were previously banned in 1985.

Asbestos is now legislated under the Control of Asbestos Regulations 2012.

48
Q

What is a deleterious material?

A

Deleterious materials were materials that were used in good fath at the time but have been proven to be a risk to buildings.

49
Q

Describe the issues with Calcium Silicate brickwork.

A

Used in lieu of concrete, often for inner leafs of cavity walls, it is susceptibel to shrinking but can perform well if used correctly.

50
Q

Describe the issues with Chloride Concrete Additives.

A

Used as an accelerator in concrete but can reduce the passivity in damp conditions.

51
Q

Describe the issues with High Alumina Cement.

A

Mainly used in pre-cast roof and floor beams produced during the 1950s-70s and is susceptible to loss of strength in hot or humid conditions.

52
Q

Described the issues with using Sea Dredged Aggregates.

A

Sea Dregeded Aggregates may contain salts which can risk corroding the reinforcement. Proper washing and treatment of the aggregate can mitigate this.

53
Q

Describe the issues with Woodwool Slabs.

A

Used as deckings for flat roofs, but can reduced fire resistance and lose strength.

54
Q

What are the indicators of wall tie corrosion?

A

Corroded wall ties will cause the opening up of horizontal mortar joints, brickwork displacement and horizontal cracking. In extreme cases, the masonry wall may bow.

55
Q

What is the remedy for wall tie corrosion?

A

Undertaking a wall tie survey to confirm the extent of the defect, followed by the removal of the existing wall ties and replacement with stainless steel ties. The wall will then need repointing to make water tight.

56
Q

You notice stepped cracks appearing in a masonry wall. What are the potential causes?

A

Stepped cracking is indicative of some form of building movement.

These can be:

  • Settlement
  • Differential Settlement
  • Heave
  • Subsidence
57
Q

You see stepped cracking and suspect this is due to ground movement. How could you identify what type of ground movement has occured?

A

Where the cracks are larger at the bottom and thinner to the top, this is most likely due to heave, which is the movement of the ground upwards.

Where the cracks are larger at the top and thinner at the bottom, this is most likely due to subsidence, which is the movement of the ground downwards.

58
Q

How would you identify lintel failure?

A

Typically a triangular shaped crack is presnt above the window to one side.

59
Q

What size of cracks are of concern?

A

Up to 2mm - Very slight
2-5mm - Slight
2-15mm - Moderate
15-25 - Severe
Over 25mm - Severe with concerns of stability

60
Q

What types of soil are susceptible to heave?

A

Clay soils

61
Q

A newly cast reinforced concrete slab is exhibiting crazing on the surface. What could be the cause?

A

Poor or inadequate curing as a result of high evaporation or lack of protection.

Excess moisture in the concrete mix and excessive floating.

62
Q

What is nail fatigue?

A

Nail fatigue occurs when a nail loses its strength, commonly due to corrosion, and the elements it is fixing together become separated. This is commonly the case with roof tiles.

Remedy may require simply using new nails, however it is likely that were one nail fails, the surrounding nails will also be susceptible to failure.

63
Q

What is a cold bridge?

A

A cold bridge occurs where two materials that are poor thermal insulators come into contact and allow heat to move through. This usually creates a spot where moisture is more likely to condense.

64
Q

How do you remedy a cold bridge?

A

The bridge must be eliminated, and replaced with materials with better insulating properties.

65
Q

How do you assess cracked brickwork?

A

BRE Digest 251 details the categories of damage from 0 - 5, where 5 represents structural damage requiring major repairs.

66
Q
A

APC Building Surveying (19 decks)

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