week 6 defects Flashcards
what is a building defect
Defective design
Defective or faulty workmanship
Defective materials or,
Failure to comply with the structural performance requirements of the National Construction Code
difference between latent and patent defects
Patent Defect. Those defects that are known or readily obvious upon inspection
Latent Defect. Those defects that are not often readily observable.
major defects are defined by
- Is the defect a major element of the building? (a fire safety system, waterproofing, or something key to the building’s stability or structure; e.g. foundations, footings, walls, roofs, beams or columns.)
- Will the defect cause or be likely to cause part or all of the building becoming uninhabitable or unable to be used for its intended purpose?
- Or, will the defect cause or be likely to cause the collapse or destruction of the building, or part of it?
list the 5 origins of defects
material failure or component failure - deteriation of finishes such as paint, metal fatigure, sprawling of clay brickwork
workmanship failure - incoreect use of fixtures and restraints
design failure
external agencies
wear and tear
explain how wall cracking defects can be categorized
damage category 1: harline fracture < 0.1mm astetically displeasing and readily repaired
damage category 4: extensive moevement 15mm - 25 mm major structural significance and repar required
Cracks are formed in concrete due to many reasons but when these cracks are very deep, it is unsafe to use that concrete structure.
Thermal Contraction/Expansion—Due to temperature changes.
Subgrade Settlement (or Expansion) - Resulting from poor soil conditions or
Drying Shrinkage—This occurs as water used in the mix design evaporates.
Changes in soil moisture content.
Differential Bearing Capacity— Harder soils under part of the foundation can cause stresses as the building “settles in.”
Applied Stresses—Forces such as building load, earth load, hydrostatic pressure, or heavy equipment operated too close to the wall.
explain common causes of concrete defects
Causes of defects in concrete structures can be broadly categorized as:
Structural deficiency resulting from errors in design, loading criteria, unexpected overloading, etc.
Structural deficiency due to construction defects.
Damage due to fire, floods, earthquakes, cyclones etc.
Damage due to chemical attack.
Damage due to marine environments.
Movement of concrete due to physical characteristics.
what is concrete cancer
Concrete cancer is caused when the steel reinforcing within a concrete slab begins to rust.
As steel rusts it can expand up to 7 times its original size causing the surrounding concrete to be displaced and become flakey.
As the steel pushes the concrete away, more water gets to the steel expediting the process. The process is often referred to as concrete spalling.
how is scaling and spaling caused
How does it occur? The process can start in many ways, but generally it is due to one of the following:
Poorly treated reinforcing steel being used when the slab is poured
The ends of the reinforcing being too close to the surface. As water seeps through the concrete it picks up limestone and other chemicals.
When it hits the steel it causes oxidation to occur in the form of rust
Incompatible metals being used in close proximity to each other, thus causing a reaction which allows water into the slab
Stress fractures from bearing weight or general wear and tear allow water to penetrate the concrete and react with the steel
Poorly installed window and door lintels are exposed to the elements causing rusting to occur
what is penetrating dampness
Rain Penetration also known as penetrating dampness is a common form of dampness in buildings. It can occur through walls, roofs, or through openings (e.g. window reveals and doors)
Water will often penetrate the outer envelope of a building and appear inside.
Common defects include:
Roof defects such as faulty flashing, cracked or missing slates or tiles.
Faults in the brickwork or masonry such as missing or cracked pointing. Porous bricks or stones.
Missing or defective mastic around windows and doors.
Blocked weep holes.
Missing or defective trays in cavity walls.
Failure of rendered finishes
difference between firable and non friable asestos
Non-Friable asbestos is any material (other than friable asbestos) that contains asbestos.
Non- friable asbestos cannot be crumbled, pulverised or reduced to a powder by hand pressure when dry.
Common uses for non-friable asbestos in buildings include: flat (fibro), corrugated or compressed asbestos cement sheets; water, drainage and flue pipes; and floor tiles.
If fire, hail, or direct activities such as water blasting and drilling damages bonded asbestos, it may become friable asbestos material
Friable asbestos material is any material that contains asbestos and is in the form of a powder or can be crumbled, pulverised or reduced to powder by hand pressure when dry.
Friable asbestos was not commonly used in the home; it was mainly used in industrial applications such as pipe lagging, sprayed limpet and asbestos cloth and rope.
Friable asbestos can only be removed by a licenced asbestos removalist with a friable asbestos licence.
key components of due diligence report
general property description
aceess
structure
building fabric
building services
external environment
Environmental Issues
Hazardous Materials Audit
Geotechnical report
Review of historical photos/ aerial view
Heritage Significance Assessment
Identification Survey
Tax Depreciation/ Capital Allowances
what is dry rot
is wood decay caused by certain species of fungi that digest parts of the wood which give the wood strength and stiffness. It was previously used to describe any decay of cured wood in ships and buildings by a fungus which resulted in a darkly colored deteriorated and cracked condition
what is concrete cancer
Concrete canceris caused when the steel reinforcing within aconcreteslab begins to rust.
As the steel rusts it expands, displacing theconcretearound it, causing it to become brittle and crack thus accelerating the process. Signs ofconcrete cancerinclude: Crazing and cracking concrete(concretespalling)
key signs of concrete cancer
Flaking and cracking concrete (concrete spalling)
Rust stains which seem to leak out from within the concrete
Bubbling ofconcrete render or
Leaks which appear in the roof or internal walls
As often as not, people mistake these signs as general weathering and dilapidation, caused by the elements; but whilst this is true to some extent and may play a part in exacerbating the problem, the real problem lies within the concrete itself.
common causes of concrete cancer
How does it occur? The process can start in many ways, but generally it is due to one of the following:
Poorly treated reinforcing steel being used when the slab is poured
The ends of the reinforcing being too close to the surface. As water seeps through the concrete it picks up limestone and other chemicals.
When it hits the steel it causes oxidation to occur in the form of rust
Incompatible metals being used in close proximity to each other, thus causing a reaction which allows water into the slab
Stress fractures from bearing weight or general wear and tear allow water to penetrate the concrete and react with the steel
Poorly installed window and door lintels are exposed to the elements causing rusting to occur
