Building Pathology Flashcards
What is building pathology?
The study of building defects, performance and failure resulting in the associated remedial action/management solutions to remedy this.
How would you identify different construction types?
Wall thicknesses - cavity and solid wall. Brick bond if visible.
Similar buildings in the area may show more. Within the roof space and the party wall.
What is a condition survey?
Aim to provide an up to date overview of the condition of a property.
Highlight any defects to repair.
Allocate resources effectively.
Allows for lifecycle costing.
Typical defect of traditional build?
Slipped tiles
Blocked gutters causing penetrating damp
Cavity wall tie failure
Debris in the cavity
Condensation damp internally from inadequate ventilation
Ineffective or breached DPC causing rising damp
Inadequate sub floor ventilation.
Typical defect of non traditional build?
Internal condensation from less thermally efficient external walls
Rebar corrosion
Blown render
How to identify a Victorian house?
Solid walls with Flemish or English bond
Suspended timber floors
Timber lintels
Timber cut roof
Slate roof
Slate DPC.
Typical Victorian defects?
Inadequate timbers to support replaced concrete or clay roof coverings
Penetrating damp - solid walls and often leaking gutters
Rotting of timber elements like windows and lintels
Lack of subfloor ventilation causing rot and decay
Rising damp caused by defective slate DPC that does not allow for movement and often cracks
Condensation as less thermally efficient.
What is damp?
Moisture within a property from an unidentified origin.
Degrades finishes and causes mould.
Types: rising, penetrating and condensation.
How to combat comdensation damp?
Warmer temperatures internally
Increased ventilation
Educate residents
Limit overcrowding
What is wall tie failure?
Common pre 1981 when galvanised steel wall ties corroded, expanded, causing movement to the external wall
Identified through horizontal cracks, every 450mm and/or bulging walls where the outer leaf has separated from the inner leaf
Wall tie replacement is possible with a borescope to identify wall ties and the replacement with stainless steel, secured by epoxy resin.
BRE Digest 251 crack identification
<0.1mm - hairline, decorative cracks.
<1mm - Fine cracks, affects the internal finishes to be treated with redecoration.
<5mm - noticeable cracks. Relining or repointing required.
5mm-15mm - Cracks cause damage. Windows and doors stick and pipes may fracture. Treat with repointing and some brickwork replacement.
15-25mm - Extensive damage with distortion of openings. Requires breaking out and replacement of wall sections.
>25mm - Structural damage with leaning walls and broken windows. Major repair job involving partial or complete rebuild.
What BRE digest helps in the identification of cracks?
BRE digest 251
What are different crack causes?
Subsidence: Downward movement of ground, loss of support from sub soil
Stepped cracking - larger at the top.
Causes: Drought causing trees to drink all water possible, especially in clayey soil; voids in ground; or drains collapsing.
Heave: where ground below the property expands, pushing the ground upwards, structural issues.
Vertical cracking.
Causes: Tree removal causing excess water, flooding, burst drains.
Settlement: downward movement due to new load of building to meet bearing capacity of the sub soil
Stepped cracking - larger at the top.
Differential settlement: where part of the foundation settles at a different rate, causing the structure to tilt.
Thermal movement.
What is cold bridging?
Area of a wall that is thermally different creating a cold spot internally, allowing moisture to condensate.
Debris in the cavity
Finlock gutters.
What types of damp are there?
Rising, penetrating, condensation.
What is rising damp?
Rising of moisture within walls through capillary action.
Up to 1.5m tide marks
Damaged wall finishes
Breached/damaged/lack of DPC
Damaged materials such as skirting
What is penetrating damp?
Moisture moving from external to internal.
Often a result of a defect such as gutters, cavity trays or unsealed openings.
Could be caused by wind driven rain.
Often localised.
What is condensation damp?
High humidity from living, insufficient ventilation and heating.
Airborne moisture condensates on colder surfaces causing black mould.
Often on external walls and around windows.
Testing for damp?
Moisture meter
Carbide testing
Relative humidity reading
How to undertake a carbide test and what BRE digest to refer to?
Refer to BRE Digest 245.
Take reading from most porous part of wall at floor junction, behind skirting if possible.
Careful to not create too much friction from drilling.
Take dust sample, combine with carbide solution to produce result.
Limitations of damp testing equipment?
Moisture meter - Meant for use on wood.
Surface reading only.
Metal in between prongs can affect the conductivity and the reading.
What is wet rot?
What BRE digest?
BRE digest 345 - recognition and control.
Moisture content > 50%.
Localised, dark look, spongey, damp smell.
What is dry rot and what BRE digest to refer to?
BRE digest 299 - recognition and control.
20-30% moisture content.
Spreads and destroys timber.
Visually light, brittle, orange/brown spots.
How to treat wet rot?
More easily treatable than dry rot.
Fix water source issue
Treat with fungicide
Replacement may be necessary
