Deleterious Materials Flashcards
(9 cards)
Concrete risks
High alumina cement (HAC): Rapid strength gain but weakens over time, esp. with moisture
Carbonation: Causes corrosion of reinforcement
Chloride attack: Accelerates reinforcement corrosion
Sulfate attack: Expands and cracks concrete in ground contact
Surveys: Cover meter, carbonation depth test, core sampling
External Envelope (Cladding & Façade) - Risks
Reynobond PE / ACM panels: Fire risk (Grenfell)
Non-fire rated insulation behind cladding
Sealant failure: Leads to water ingress
Delaminating render systems
Remedies:
Fire risk assessments, recladding, EWS1 form
Replace non-compliant systems
Glass Risks
Non-safety glass in critical areas (Approved Doc K / BS 6262)
Nickel sulphide inclusion: Causes spontaneous breakage in toughened glass
Single glazing: Poor insulation and condensation risk
Checks: Safety markings, manifestation, building regs compliance
Hazardous Materials examples and actions
Examples:
- Asbestos (lagging, AIB, floor tiles)
- Lead paint (pre-1970s)
- Polychlorinated Biphenyls (PCBs) – old lighting ballasts
- Radon gas – geographic risk areas
- Actions:
- Refurb & demolition asbestos surveys
- Encapsulate or remove
- Ensure licensed removal contractors
Insulation risks and remedies
- Urea formaldehyde foam: Off-gassing, can degrade masonry ties
- Combustible insulation (e.g., PIR, EPS): Fire risk in high-rise
- Moisture ingress: Reduces thermal efficiency, risk of mould
Remedies:
- Remove/replace with compliant insulation
- Ensure correct ventilation around insulation
Metal risks and remedies
- Corroding wall ties: Expansion cracks, structural risk
- Aluminium and steel cladding: Oxidation, corrosion
- Copper/aluminium roofing interfaces: Bimetallic corrosion
Solutions:
- Wall tie surveys
- Replace or protect corroded elements
Plaster risks and remedies
- Magnesium oxychloride (“Sorel”) plaster: Delaminates in moist conditions
- Cracking: From movement or shrinkage
- Inappropriate gypsum plaster on solid walls traps moisture
- Remedies:
- Remove Sorel plaster
- Use breathable lime plaster where appropriate
- Replaster with correct material
Structural risks and solutions
- RAAC (Reinforced Autoclaved Aerated Concrete) – brittle, no warning before failure
- Corroding steel frames (hidden in concrete or brickwork)
- Overloading of joists or beams
Surveys: Structural engineer assessment, opening-up works, intrusive inspection
Wood / Timber risks and actions
- CCA-treated timber: Contains arsenic (now restricted)
- Wet/dry rot from moisture exposure
- Insect attack – woodworm, deathwatch beetle
- Inappropriate timber in structural locations (undersized, untreated)
Actions:
- Replace decayed timber
- Treat or improve ventilation
- Assess structural adequacy
