Case Study Flashcards
(80 cards)
1
Q
What form of condition survey did you produce initially relating to CIF?
A
Condition Report
- Level 1 Survey
- RAG system / CDC Condition Ratings
D1 - A4
2
Q
Were there any other issues other than the windows?
A
- Roof felt was exhibiting some defects
- However at the time the windows and piers were priority due to immediate risk for health and safety
- Some spalled brickwork
- Polycarbonate roof at GF level was in poor condition
- Inner courtyard windows were exhibiting some defects
- Internal plaster finishes
- Penetrating damp visible to some areas
- Poor flooring finishes
- Electrical lighting faults
3
Q
Given the buildings age, what sort of common defects / issues would you anticipated being present?
A
- Asbestos
- RAAC
- Damp / Condensation
- External brickwork and Mortar
- Roofing defects
- Concrete defects
- Cavity wall tie failure
- Structual issues / Subsidence
- Electrical Systems
- Fire doors
- Fire detection layout
4
Q
Explain the competitive tender process? How were SDC appointed?
A
- Produced the design and specification
- Selective contractor competitive tender process
- 4 Contractors were invited to tender for these works
- SDC were appointed due to being the most cost effective as well as a compliant good quality return
- Following due diligence checks on financial accounts and insurance cover and case studies, analysis of tender return contract sum analysis their return was found to be free of errors and within the expected costs
- Usually an annual turnover of 3-4 times the project amount is a good principle to use for financial health status aligning for the project
- Undertook pre qualification queries and was satisfied with the responses provided by SDC
- Agreed a start date of 17th July with a 9 week programme overall for all 3 sections
5
Q
Did you use a letter of intent / client PO or contract to appoint them?
A
- Contract was prepared within 2 weeks revisit stage
6
Q
How did you select the JCT Intermediate WCD 2016?
A
- Works were of medium scale complexity and cost
- Subcontracted specialist works for concrete repairs
- Design element for fabrication of windows as per specification
- Works required to be split into sections, 3 weeks per section
7
Q
Programme - How did you calculate the construction phase timeframes?
A
- Made sensible assumptions based off previous experience and historical data within the team
- Collaboration with contractors to understand capabilities
8
Q
How did you structure your detailed report?
A
- Site address and contact details
- Purpose of the survey
- Survey conditions, weather time etc
- Limitations / access
- Photographs and condition ratings
- Conclusions / recommendations
9
Q
What were the high priority works required?
A
- Windows to Sports Halls
- Brick pier facade rectifications
- Windows to classrooms and kitchen
- Roof
- Concrete degradation to lintels
- Windows, concrete lintels, and piers were deemed as highest priority due to immediate health and safety risk
10
Q
How did you assess the windows to be the most urgent?
A
- Immediate replacement required due to health and safety concerns over the opening of windows and visible deterioration to windows and concrete lintels spalling
11
Q
How was the budget calculated as sufficient?
A
- Competitive tender exercise undertaken to form the cost document to prove cost certainty submitted to the DfE
- Professional fees and investigative costs pre calculated
- Provisional sum allowed
- Contingency sum allowed for any unforeseen works
12
Q
What are the typical defects of a 1960s school block?
A
- Windows and doors from ageing and poor quality materials
- Roof defects due to ageing and deterioration
- Damp and condensation issues due to failing external elements and poor ventilation
- Cracking and damage to walls from subsidence or settlement
- Electrical faults due to age of systems
- Asbestos containing materials
- Possibility of RAAC
- Internal finishes and material degradation from damp
- Fire door issues
- Fire alarm and detection not providing adequate coverage
- External walls and bricks and mortar degradation
13
Q
What type of defects would you expect to find in a cavity wall construction?
A
Cavity wall tie failure
- Corrosion to steel wall ties
- Leads to structural movement of walls
- Leads to degradation of mortars through expansion of ties, leading to further damage
Bootleg lintel defects
- Lintels rotate due to differential loads applied to inner skin and outer skin brick and block
- Lintel degradation due to frost damage and carbonation
Lack of or aged insulation
Condensation
14
Q
How did you determine a steel and concrete frame?
A
- Sports hall ceilings were exposed and concrete and steel columns could be seen with steel cross beams for the roof structure
15
Q
What are the typical defects of steel and concrete frames?
A
Concrete defects
- Carbonation
- Concrete spalling
- Surface delamination
- Poor worksmanship and concrete mix at time of installation for concrete cast in-situ
Steel
- Corrosion
- Welding defects
- Movement due to subsidence
- Design flaws
16
Q
What was the roof finish? Was there any defects?
A
- Bitumen felt roof with tapered insulation
- Exhibiting some defects
- Blistering
- Moss growth
- Blockage of drains
17
Q
What were the defects you found in the steel windows?
A
- Unsafe opening widths with no restriction fitted
- Excessive condensation build up due to poor thermal properties and lack of ventilation
- Corroded frames
- Broken glass panes
- Water penetration through edges of windows with no insulation present causing degradation to internal finishes
- Paint finish flaking and peeling
- Rust staining on glass
- Gaps around window frames
18
Q
What are the risks of reinforced concrete lintels?
A
- Carbonation leading to alkinity in concrete protection to steels lowering and breaking away
- Steel reinforcement corrosion
- Concrete spalling due to frost damage and multiple freeze thaw cycles
- Exposed to weathering and deterioration
- Increased risk of structural failure over time
- Structural loads and improper design
- Insufficient design methods such as boot lintels
- Expansion and contraction
19
Q
What do you mean by inception to completion?
A
- Entire lifecycle of the project from initiation and initial survey to completion of the project
20
Q
What are typical defects with windows and doors?
A
- Deteriorated sealants
- Insufficient opening and closing
- Defective hinges and mechanisms
- Corrosion to steels lowering frames
- Insufficient thermal performance
- Insufficient ventilation
- Excessive gaps to surrounds
- Condensation
21
Q
What were the concrete repairs specified?
A
- Brush off existing steel corrosion and concrete and prepare surface
- Apply zinc modified primer
- To provide protection for steel, acts as a bonding agent for the concrete, can be sprayed or manually applied - Repair mortars
- To build back up to original profile and restore structural integrity - Pore filler and levelling mortar
- Concrete protection
22
Q
How were the concrete repairs specified?
A
- Refer to BS8500 for concrete specifications
- Undertook research on suitable concrete repairs
- Undertake CPDs on appropriate concrete repairs systems
- Checked sika specifications on website technical details
- Used tools such as NBS source
23
Q
What is the minimum coverage for concrete?
A
- Minimum concrete coverage is 40mm
- 75mm for concrete in direct contact with soils or in marine environments
24
Q
What specialist surveys did you coordinate?
A
Concrete hammer test
- Tool used to rebound a spring to measure compressive strength of the concrete
R&D survey
- Identify any asbestos containing materials associated with the works
25
How did you manage the tense process?
- Selective competitive tender process
- 4 contractors invited to tender for the works
- 4 week tender period
26
How do you review the contractors proposals?
- Reviewed the site access plan against the proposed plan submitted with the PCI
- Reviewed teleflex gearing proposal against contract specifications and requirements
- Reviewed fabrication proposals of windows, comparing extrusions, millions and transoms with those submitted in tender drawing
- Accepted proposals to proceed with
27
What are the advantages and limitations of aluminium windows and doors?
Advantages
- Robust and high in strength frames with long life span
- Little to no maintenance required
- Aesthetics, slim slender design
- High thermal performance through thermally broken extrusions to provide a cavity within the frames
Disadvantages
- Higher cost than uPVC windows and doors
- Suseptible to scratching which can be difficult to repair
- Expansion and contraction risk of frames
28
Why is the windows restricted to 100mm openings?
- As per building regulations Part K, regulations for areas where there is a risk of falling
29
How did you determine the guarantee requirement?
- Reviewed manufacturer warranty on materials
- FENSA specifies 10 years for aluminium windows
30
What did you do to ensure building regulations compliance? Building regulations and British standards?
British Standards
- BS 4873 - Aluminium Windows and Doors
- BS 6262 - Glazing
- BS 6375 - Security / Fire resistance / Impact Resistance / Weathertightness
Building Regulations
Part B Fire
- Means of escape from habitable rooms at first floor
- Windows along fire escape route will need to be fire rated
Part C Resistance to Moisture
- Requirement for insulated window jambs
- Standard detail on ADC
Part F Ventilation
- Requirement for background ventilation table with measurements
Part K Protection from Falling, Collision and Impact
- Safety glazing for any windows below 800mm from FFL
- Opening restricted to 100mm
Part L Conservation of Fuel and Energy
- Thermal performance 0.16Wm2/K
Part M Access to and Use of Buildings
- Level door threshold for access
31
What are preliminaries in a contract sum?
- Items required for the contractor to complete the works, I.e access, site management and supervision, insurances, protection, services, site set up
32
How did you calculate a contingency sum?
- A sensible industry wide approach is to allocate at least a 5-10% of the budgeted construction costs
- In this case £15k at circa 5-6%
33
What were the extension of times per section?
- Section 2 - One week
- Section 3 - Two weeks
34
What makes aluminium perform higher in terms of thermal insulation compared to existing?
- Thermal break in window frames to improved thermal efficiency
- Aluminium has higher insulating properties
- Double glazed window units with solar shading properties to allow light transmittance and control solar gain for reduce in energy waste in line with Part L and Part
- More resistant to condensation providing installed correctly
35
What deleterious materials would you expect to expect within this building?
- Asbestos
- RAAC
- Lead based paint
- Legionella
36
How did you assess worksmanship guarantee?
- Understand the covered elements of the works
- Requirements for maintenance and upholding guarantee
- Exclusions from the guarantee
- Credibility of the contractor
- Understand the process for claims
- Check the duration, project details and contacts
37
What was the contractor design portion and why?
- Final window dimensions and fabrication proposals to be submitted
- Teleflex hearing for high level sports hall windows
- Site access plan and scaffolding to top of banks for sports halls
38
The brick piers were uneven, should you have thought there were was an issue with lack of tying in when undertaken initial survey?
- Yes I did, therefore undertook investigations to remove 2nr bricks from high level to investigate whether tied in and it wasn’t
- I advised the area to cordon external areas off until the works had been complete
39
Curing time for mortar a potential issue - what is max height of masonry in a day?
- Maximum height of 1500mm or 20 courses per day
- BS8000 and NHBC standards
40
Insulated cladding option - what have been recent high profile cladding issues with insulated cladding (Grenfell style insulation - describe it and the issue)?
- Grenfell - Aluminium composite material which was highly flammable and caused the fire to spread quickly among the external wall
- All cladding to high risk buildings over 18m should have a fire class A
- Cladding for buildings under 18m but within 1m of the boundary must be at least B
- Rating of B was specified for cladding - Limited combustibility and limited contribution to fire
- BS 8414 - Fire performance of external cladding systems
41
What is a bootleg lintel? What are the main issues?
- Two sections of concrete which is supported by the bearings on the inner skin of the wall therefore no requirement for bearings to either side of the external support
- Used in older buildings to cut costs
Common issues
- Rotation of the lintel due to excessive loads on outer skin support, causing cracks to external wall and internal wall above corners of windows
- Improper design and structural loading calculations
- Vulnerable to corrosion over time
- Uneven distribution of loads
- Stepped cracks to brickwork above windows and doors
42
Curtain walling - How much of a risk to planning was this?
- Risk was low due to the timing
- Ample time at design stage for consultation
43
What was the u value of the new window?
- 0.16Wm2/K in line with Building Regulations Part L - Conservation of fuel and energy
44
Describe the specification of the windows?
- u value of 0.16Wm2/K in line with Building Regulations Part L - Conservation of fuel and energy
- Kestrel Aluminium 60mm System with thermally broken frame millions and transoms to provide a cavity between the outer and inner skin of the window, top hung window opening lights with fold openers, 28mm toughened double glazing with 4mm glass panes with solar shading properties to limit solar gain in line with Part O, trickle vents installed to top of each window unit as per Part F, tele-flex gearing for high level windows, satin laminated glass for sports hall windows for increased impact resistance with 6.8mm glass panes, glass panes internally beaded for security, openers restricted to 100mm as per Park K
45
What is a DEC certificate?
- DEC certificate displays the buildings actual energy usage over the previous 12 months
- Hall Green Case Study has a rating of C
46
What is an EPC certificate?
- Energy performance certificate required when buying or letting a property
- Minimum rating of E required for rented properties as per the MEES
47
How did you determine the bricks were facing and not structural?
- Internal structural columns were exposed
- The roof structure was supported by steel beams bolted to the inner flange of the steel columns
- The brickwork and windows stand proud and the outer flange of the steel columns are packed out with reinforced concrete
- Structural engineer was appointed to confirm this
48
What is the construction of the sports halls?
- Both sports halls are steel beams for the flat roof supported by steel columns bolted to the inner flange with the outer flange encased in concrete
- The encasement packs the gap between the outer flange and original brickwork and window
- The intermediate window support post is a precast reinforced concrete column which is trimmed at eaves level with an in-situ reinforced concrete beam in which the boot lintels are encased
- There is an internal longitudinal steel channel bolted to the inner steel column flange which is the column restraint
- The existing window frames are cleated to the front of the columns and windows are proud of the column face
49
How were the bricks defective?
- Uneven construction as seen on then photographs and it was suspected that they were not tied into the supporting concrete columns
50
51
How did you investigate the facing bricks?
- Appointed a contractor to have the top tow courses of brick removed to check whether they were tied into the columns, and as expected, they weren’t
52
What was the supporting structure? How would you expect the bricks to be tied into it?
- I would expect to see galvanised steel ties fixed at appropriate centres every 600mm from embedded mortar of the bricks into the concrete column with a minimum depth of 50mm
53
Why would you match the existing profile and colour?
- In line with planning requirements for like for like system
54
How did you advise your client longer construction period for Option 1 bricks to be laid and tied back?
- Reviewed the relevant BS8000 workmanship for masonry which outlines a maximum of 1.5m or 20 courses of bricks per day, would require at least one more week to undertake
55
What is the curing time for mortar when laying bricks?
- BS8000 states 24-48 hours, full strength after 28 days
56
Did the cladding panels need to be fire rated?
- No, refer to ADB and the Fire Safety Act 2021
- As the building is less than 18m and not within 1m of the boundary, the cladding did not need to be fire rated
- Howver I did specify a Euroclass rating of at least a B which provides minimal contribution to fire spread
57
What guidance did you follow when specifying the cladding and insulation option?
- Building Regulations Part B
- Building Regulations Part L
- BS 8414 - Fire performance of external cladding systems
- U Value 0.26
58
How did you advise regarding a continuous lintel?
- Achieved by shuttering the infills with timber ply shuttering and concrete encasement
- Dowel bars resin anchored to adjacent concrete lintels following rebar scan by 100mm, 10mm diameter anchors
59
Did you design the continuous lintel yourself?
- I designed the finish and build up
- Structural engineer provided detail for the structural connection
60
Why were bootleg lintels used?
- Post war condition method
- Provided cost savings
- Scarecity of pre fabricated lintels during the period
- Lack of building codes and regulations led to improper design and construction
61
Why would option 2 require planning permission?
- Change of material and appearance
- Could be seen from public highway
- Contacted local planning offer and they confirmed and application would be required to change the bricks
62
What is a curtain walling system? What are the advantages and disadvantages of curtain walls?
- Non structural external building facade made up of framework and glass
Advantages
- Appearance of a glass wall design
- Increased energy performance
- Durability and weather resistant
Disadvantages
- Initial costs
- Costs for maintenance if damaged
- Risk of glass breakage
63
What is the construction build up of the insulated panels?
- Clean and prepare the surface of the concrete
- Apply VCL for moisture resistance and aluminium flashings to entire length
- Timber battens for fixing cladding
- 100mm PIR insulation
- uPVC cladding with a euroclass rating of B with limited ability to contribute to fire
64
How was the structural engineer appointed?
- Appointed during the project to provide advice on structural elements and design on a day charge basis of £750 per day
65
What is carbonation?
- The process of the carbon dioxide in the atmosphere reacting with the calcium hydroxide of concrete
- Over time this breaks down the alkalinity level of the concrete which provides the coverage and strength of the steel reinforcement and produces calcium carbonate
- Over time this continues to break down leading to steel reinforcement being exposed
- Steel reinforcement then has no protection against moisture and leads to expansions from rusting, further breaking away the conference and exasperating the issues
66
How does the zinc modified primer protect the steel?
- Provides a sacrificial layer on top of the steel to protect against corrosion
67
What is cathodic protection?
- Cathodic protection isa method for preventing corrosion to metal surfaces usually used in extreme wet and marine conditions
- A sacrificial cathode is applied to the metal lowering its corrosion potential
68
Why did you select the Sika product?
- Good reputation in concrete repairs systems, also attended CPD to understand how their concrete repair systems work
- Approved product on NBS source which is used to produce specifications
- Well known manufacturer who provide quality assurances of their products
69
How did you identify and confirm carbonation?
- Visually inspected and the nature of the defects identified corresponded with the defects
70
How did you identify and confirm carbonation?
- Visually inspected and the nature of the defects identified corresponded with the defects associated with concrete carbonation
- Following engagement with the concrete specialist, I instituted a phenalythaeilt test to be undertaken on site to condfirm carbonation using a chemical spray which shows pink colour for areas that are not suffering from carbonation, there was patches of no colour and pink to some areas which confirmed carbonation and low levels of alkanility
71
What other ways can concrete suffer from corrosion?
Multiple freeze thaw cycles
- Moisture ingress into small cracks which form over time in concrete and freeze during freezing conditions which leads to further cracks and concrete degradation
Chloride attack
- Chloride ions often from seawater can penetrate the concrete
- The ions react with the steel causing corrosion and rusting of the steel
- The rust expands creating stress and cracking in the concrete
72
Where did the remedial specification come from?
- This was the same specification and build up specified at design stage for the concrete lintel repairs
- Sika System complete 4 layer inciting zinc modified primer, repair mortars, pore filler and levelling mortar and concrete protection paint covering
73
100+ year life expectancy of steel columns, where did this come from?
- BCIS Life expectancy of components and materials states 60+ years
- Reknown manufacturers such as Teta confirms a 140 year life expectancy if properly maintained
- Reasonable middle ground was advised to the client
74
Why did you suspect carbonation?
- Done by ruling out other possible causes
- Such as freeze thaw cycles, the the concrete was encased in bricks and no present of rainwater ingress
- Chloride attack is more common in marine conditions from seawater
- Carbonation is a common defect in buildings built around 1960s
- Concrete was still in situ prior to the removal of windows and broke away upon removal of the windows indicating progressive weakening of the concrete
75
How did you test for carbonation? And what is the limitations of this testing?
- Concrete specialist engaged to undertake phenalyhaylene testing
- Sprayed onto affected areas which indicates ph level of the concrete, pink indication high alkaline and colourless indicating low alkaline and weakening of concrete
- Limitations of this testing is that it is a surface test only and may give false indications if concrete is wet from rain
76
What is the risk of exposed steel reinforcement?
- Exposed steel reinforcement leads to corrosion and over time weaking of the tensile strength of the concrete and failure of steel reinforcement loses its connections
77
What other factors can exacerbate the risk of corrosion to steel?
- Improper construction methods during the post war period, insufficient coverings to the steel reinforcement
- Poor concrete mix for concrete poured on site with high water to cement ratio leading to increased porosity and more susceptible to moisture penetration
- Environmental exposure to salts leading to chloride attack usually in marine condition
78
What is the design guidance for required concrete coverage?
- BS 8500
- States design guidance and standards for concrete
79
With option 3 how would the steel columns have been constructed?
- Would have to restrict access into sports halls throughout the duration of the works
- Temporarily protect and prop the steel roof structure with strong boys and acro props
- Remove and dispose of existing columns
- Prpare the foundation surface for new steel base plate and resin anchor with bolts to structural engineer design
- Bolt back into the roof steel beams
- Undertake the associate wall and finish repairs in preparation for installation of the new windows
80
What is the recommended coverage on steel reinforcement?
- The minimum coverage is 40mm
- Some areas depending on whether in contact with soils or in marine conditions, the recommended coverage is 75mm
