Important cards

Question 1

CAn you name deleterious materials?

Answer 1

1. Asbestos (carcinogen, mesothemlioma)
2. Lead (toxic if inhaled/injested)
3. Woodwool slab (stability loss, shuttering)
4. Aluminium composite materials- sandwich panels (PIR/PUR fire risk)
5. Hair plaster (anthrax - COSHH)
6. High Alumina Cement (loss stability)
7. Clinker concrete - filler joist floors (steel corrosion)
8. toughened glass nickel sulphide inclusions used within planar glass frame
9. Mundic (stability loss sulphate degradation)
10. calcium silica bricks (cracking and shrinkage)
11. brick slips adn tesserae (loss adhesion)
12. CFS refridgerants R22 (Ozone depletion)
13. Urea Formaldehyde foam (cavity walls - carcinogen)
14. MMMF man made mineral fibres (carcinogen) glass fibre loft insulation
15. Reinforced Autoclaved Aerated Concrete (RAAC) planks (loss stability)

Question 2

What are clay hollow pot floors and why are they problematic?

Answer 2

1. Hollow clay pots (tiles) were first used early in the 20th Century as a means of constructing fire-proof floors and reducing some of the dead loads of solid construction
2. The pots were separated with a clay spacer, and steel reinforcement bars were placed within the gap this formed, with a concrete structural topping being laid over the top of the pots and filling the gaps between
3. Poor compaction (similar to the problem with woodwool slab) between the pots can lead to voiding and a lack of cover around the reinforcement, reducing the floor’s fire resistance, durability and strength

Question 3

What are the main problems associated with composite panels?

Answer 3

• Composite panels are a sandwich construction of which two outer layers of steel or aluminium sheet enclose an inner core of an adhesive-bonded lightweight material, e.g. polyurethane foam (PUR), polyisocyanurate foam (PIR), expanded polystyrene (EPS)
• These materials can burn fiercely, give off thick black smoke and produce burning droplets that can fall on whatever lies beneath, making them very difficult to deal with

Question 4

What is the key difference between PIR foam and PUR foam used in composite panels?

Answer 4

The fire resistance is significantly lower in PUR (degrades at 250°C) than in PIR (degrades at 400°C)

Question 5

What is interstitial condensation?

Answer 5

Interstitial condensation is condensation that occurs within a void or cavity where there is insufficient

1. ventilation
2. insulation
3. or absence of a vapour control layer

Question 6

What is thermal bridging?

Answer 6

• Thermal bridging, often known as cold bridging, is caused where there is direct contact between internal and external faces of a building due to thermal properties of the fabric being poorer than that around the area.
• wasteful heat transfer across this element - heat loss as the heat conducts from warm to cold area.
• Often viewed with a thermographic camera
• Will often cause localised condensation and therefore mould growth
• Insulation is a thermal break which stops heat transfer
• Thermal bridges can be categorised as ‘repeating’ for example where wall ties regularly bridge the cavity, or ‘non-repeating’ such as a wall junction or lintel.
• The Approved Documents to Part L of the building regulations (Conservation of fuel and power) state that ‘The building fabric should be constructed so that there are no reasonably avoidable thermal bridges in the insulation layers caused by gaps within the various elements, at the joints between elements and at the edges of elements such as those around window and door openings.’

Question 7

What is Regent’s Street Disease?

Answer 7

• The corrosion of the steel frames within masonry clad buildings.
• Its so called because a lot of the buildings on regents street are built around early to mid 1900s and have masonuary packed tightely around their steel frames.
• These leaves no room for expansion, if moisutre gets inside the facade the steelwork can corrode, it then expands massively and causes damage to the stonework such as cracking and spalling and in severe cases falling masonary.
• 1900s to 1950 builders packed masonry tight around the framework, leaving no room for the steel to expand.
• Rain can permeate the porous facade stone or brickwork corrode the steelwork or it can be moist air inside the cavity from inside the building.
• Corroded steel exapands in volume and can cause stonework to spall and leading to falling masonary which is dangerous

Question 8

What remedial works might you suggest for Regent’s Street disease?

Answer 8

1. Temporary resin stitch repairs to tie loose masonary
2. Retained facade, renew steel structure
3. Remove cladding, remove rust from steel and treat with a corrosion inhibitor and repair
4. Cathodic protection.
5. There are temporary solutions such as stitching loose masonry together with resin on fixed stainless-steel bars at the affected area. Other methods may help just delaying the inevitable.

The only way to resolve it permanently, as has been successfully done on many buildings in Regent Street, is to retain the façade but replace the entire steel frame with a new, purpose-built frame, constructed back from the masonry. The masonry is then fixed to the new “web” using stainless steel secondary fixings.

Repairing the façade steelwork is an extensive but effective method – provided it is carried out correctly.This work involves removing the masonry cladding and the surface rust by blasting the existing steel before treating it with a protective coating/paint.

Cathodic protection, a less invasive method, involves reducing the corrosion process by running an electrical current through the corroded steelwork.

Cathodic protection (CP) is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects the metal to be protected to a more easily corroded “sacrificial metal” to act as the anode

DC current from the environment into the protected metal surface to reverse the direction of electric currents associated with the corrosion process. It does not make good previous corrosion but suppresses the continuation of the process.

Question 9

Can you name some typical defects you might find in a victorian property?

Answer 9

1. roof spread - poorly supported roofs
2. nail fatigue
3. Structural issues -soil movement shallow foundations make more suceptible
4. Weathered brickwork from pollution acide rian, masonary bees, in appropriate repairs.
5. penetrating damp throguh single skin walls failure of the damp proof course.
6. chimney leaning sulphate attack (products of burning, hydroscopic salts), poor flashing, water ingress missing flanching, weathering. missing pots
7. Defective rainwater goods cast iron
8. Lead paint and lead water supply pipes
9. Water ingress through parapet walls -
10. Bay window differential movement
11. Poor sub floor ventilation - dry rot
12. Dated service installations
13. later additions 1960s back boilers
14. Asbestos likely to have been added later on
15. Water ingress to basements

Question 10

Can you name som concrete defects?

Answer 10

1. Carbonation - phenol phalein test
2. Chloride attack
3. Concrete cancer Alkali-silica Reaction (moisture and high alkali content)
4. High alumina cement
5. Sulphate attack
6. Mundic and Bungaroosh
7. Fire damage
8. Lack of concrete cover and honeycombing (poor concrete mix)
   9.

Question 11

What is the difference between dry and wet rot?

Answer 11

• Wet rot is confined to the area of damp timber whereas dry rot can spread and affect timbers some distance away from the source of damp.
• They are cause by different species of fungus
  
  • Wet rot is caused by Coniophora puteana
  • Dry rot is caused by serpula lacrymans
• They prefer different moisure levels
  
  • Wet rot grows at a higher moisurte level 50% +
  • Dry rot 20-30%
• Wet rot you tend to see the wood turn black whereas dry rot you see rusty dust like brownmarks where you can see a fruiting body which contains the spores. Mycelium are white turning grey with age.
• Dry rot grows in a dark humid environement inside the building such as in a roof void or under a timber foor whereas wet rot can be on external timbers.
• Dry rot you might see cuboidal cracking on the skirting boards but this tends to be hidden behind paintwork, timber is crumbley.
• Wet rot the wood turns soft nd spongey with the fibres showing
• Dry rot smells of mushrooms!
• Recognising wood rot and insect damage in buildings. BR 453

Question 12

What are the different types of damp?

Answer 12

1. condensation -
   
   1. warm moist air within a property condenses ona cold surface which is below the dew point forming water droplets on the surface.
   2. Black mould growth on cold surfaces such as outside wall when internal relative humidity is high and there is insufficient ventilation
   3. Interstitial condensation occurs within or between the layers of the building envelope, e.g. water vapour enters the roof void and condensation has occurred to the cold underside of flat roof decking
2. Rising damp
   
   1. damp which rises from ground level and wicks up porous materials by capilliary action
   2. Caused by
      
      1. High water table
      2. failure or bridging of damp proof course
   3. wavy tide mark up to 1 metre high of salts and water staining on internal finishes
3. Penetrating damp
   
   1. rainwater entering the building - defective rainwater goods, poorly fitting windows
   2. Services leaks
      
      1. Infrared thermography can be useful here, because this technique will identify surface temperatures that can be linked to symptoms of dampnes
   3. flooding
   4. Reference BRE

Understanding dampness BR 466

Question 13

Can you tell me different patterns of structural cracking and what they might mean for a building?

Answer 13

1. Horizontal cracking to brick work/stone
   
   1. wall tie failure (cavity walls)
   2. Regents street disease
2. Stepped cracking wider at bottom than the top
   
   1. Heave
3. Stepped cracking wider at the top than the bottom throuhg brick and mortar
   
   1. subsidence
4. Stepped cracking either side above a lintel/brick arch
   
   1. lintel failure
5. Hairline cracking at wall and ceiling joints
   
   1. Shrinkage
   2. Settlement - usually of a new build
6. Large 5mm+ cracks or multiples of 3mm between a house and an extention or a bay window
   
   1. Differential movement.
7. Vertical cracking on a steel framed structure or between two different materials
   
   1. thermal expansion
8. Large scale cracking and sudden damage.
   
   1. sink holes
   2. mines.

Question 14

How can you record damp in buildings?

Answer 14

1. Oven Drying (Gravimetric Testing)
2. Conductance Meter (aka Protimeter)
3. Carbide Testing (aka Speedy Meter)

Question 15

Explain how carbide testing can be used to measure damp.

Answer 15

1. Used for masonry products (e.g. bricks, blocks, mortars etc.)
2. Material is drilled slowly to minimise heating (and thus drying) then weighed and placed in a container
3. Specific amount of calcium carbide is added and container is sealed
4. Container vigorously shaken so two materials mix
5. Moisture in sample reacts with calcium carbide to produce acetylene gas, causing pressure inside the container, which gives a reading on the pressure gauge

Question 16

How would you identify penetrating damp within a building?

Answer 16

1. Distinct damp patches with well-defined edges
2. Often in localised areas
3. Moisture readings show sharp change from wet to dry
4. Patches of efflorescence (crystallisation of sulphates and carbonates present in building materials)
5. Timber in area of damp has high moisture content
6. External inspection may reveal obvious defects (e.g. cracked render/brickwork, damaged downpipes etc.)
7. Deep wall probes indicate high readings in centre of wall
8. Line of dampness on internal plasterwork corresponding with mortar joints where cement mortar/dense wall materials have been used
9. Measure wall temperature, air temperature and RH to eliminate condensation
10. Salt analysis shows zero level of nitrates and chlorides, eliminating rising damp

Question 17

How would you identify penetrating damp within a building?

Answer 17

1. Distinct damp patches with well-defined edges
2. Often in localised areas
3. Moisture readings show sharp change from wet to dry
4. Patches of efflorescence (crystallisation of sulphates and carbonates present in building materials)
5. Timber in area of damp has high moisture content
6. External inspection may reveal obvious defects (e.g. cracked render/brickwork, damaged downpipes etc.)
7. Deep wall probes indicate high readings in centre of wall
8. Line of dampness on internal plasterwork corresponding with mortar joints where cement mortar/dense wall materials have been used
9. Measure wall temperature, air temperature and RH to eliminate condensation
10. Salt analysis shows zero level of nitrates and chlorides, eliminating rising damp

Question 18

Typical defects within cladding?

Answer 18

• blocked cavity in rainscreen cladding preventing water draining away
• nickel sulphide inclusions in planar glazing
• poor or failed fixings.
• Mechanical Impact damage from crades
• ccracking from thermal expansion brise soleil baguettes GRC
• Movement of the structural frame.
• Aluminium composite materials - combustible insulation
• Corrosion - galvanic, filiform corrosion
• Lack of ashesion tesserae soandrel panels
• Erosion and staining - lime stone panels, pollution