Case Study Flashcards
What was the health and safety incident?
- Slipped roof tile into external nursery courtyard on 1st floor
How did you ensure health and safety of the site?
- Erected a scaffold in the area of incident and along severely cracked parapets
- Ensured scaffold had debris netting and monoflex, safe access ladders and was checked weekly
- Visited site to assess the condition of the building to provide recommendations to the client
A structural report was commissioned before your involvement. Why did you visit with another structural engineer?
- To provide clarity on the 1st engineer’s report
- To confirm my recommendation of Roof 1 replacement and parapet repairs
- To ensure the building was structurally sound
What considerations did you undertake in respect of the local listing?
- Liaised with LBH’s conservation officer (CO) and issued schedule of works
- CO advised:
o Planning permission not required for repairs
o Inclusion of lime mortars only for brickwork / repointing
How can you tell the building is constructed of solid walls?
- 2 bricks wide, interlocking bricks with no gap in the middle
- Mixture of header and stretcher bricks
What is clinker? How did you establish it was clinker?
- A fused material produced at high temperatures – a waste material from coal-fired glass furnaces
- Produced by heating limestone and clay to liquefaction around 1,400-1,500 degrees
- Composition of the slab typical for age of building
- Could have sent the clinker to a lab for testing, however I considered the time and cost implications and advised the client this was not necessary
What procurement route did you use and why?
- Traditional, single-stage
- Fully designed when going to tender, allowing for the client to secure a competitive price
- Allowed for cost certainty before works commenced
Why did you choose a minor works contract?
- Works simple in nature
- Lasted less than 12 months (8 months in total)
- Client / consultant responsible for procuring all of the design
- No requirement for bonds or completing work in sections
What cause the significant cost increase from Contract Sum to final account?
- Change of personnel within the client – new client was more involved in the process and so secured a larger budget
- Some of the areas of the building only reached after full scaffold erected
- Original scope of H&S was expanded to undertake maintenance works
- Included rates within the contract – e.g. for repointing, rebuilding brickwork, additional windows, replacement of coping stones
o Ensured priced given were fair and reasonable
How did you select the contractors?
- Proposed 3no. contractors to client who undertake works of this nature / size
- Barker have vetting process which requests they submit details of their:
o Turnover
o Company information – directors
o Similar case studies with references
o Information on typical size of projects - Client put forward 3no. contractors of their own
- All had to be accredited on Constructionline
How did you provide regular updates?
- Visited site weekly and issued inspection reports
- Called the client / stakeholders every 2 weeks
- Monthly formal progress meetings with project team
What was included in your site inspection reports?
- Labour levels on site
- Progress of work
- Weather details
- Any requests for further information with the site manager
- Any contract instructions discussed / proposed
- Photos detailing progress
- Items with specific actions for members of the project team
Why were the works notifiable?
- Last longer than 30 working days AND have more than 20 workers on site, OR
- Exceed 500 person days
Why did you choose to appoint an approved inspector?
- Cheaper than council-appointed building control
- Able to get quicker responses
What pre-construction risks did your designers identify?
- Unauthorised access onto site – specified fencing / hoarding, signing in/out system
- Falls from height – erecting safe platforms / scaffolding that were checked weekly
- Dust – using monoflex / debris netting when undertaking repointing. Undertaking on days when building less busy. Uisng dust suppression on power tools.
- Potential asbestos – undertake R&D survey before works commence on site
- Manual handling - hoist for scaffold, sharing heavy loads, wearing appropriate PPE
- Noisy works - appropriate PPE, noise suppresion on tools, notifying tenants of when noisy works were being undertaken throughout the week
What residual risks did you identify?
- Future use of terrace areas – incorporated railings
- Inspection of Roof 1 & Roof 4 – installed new railings with access ladders
- Monitoring of chimney leaning into building
o Referred to structural engineer who recommended 3-monthly monitoring - Asbestos – undertook a Refurbishment & demolition survey to advise on locations of asbestos (nothing). Advised building manager to update their asbestos management survey
- Flat roofs - to ensure compliance with the gurantee, advised that the building undertakes maintenance such as clearing the roof and RWGs of dirt / debris
What defects did you identify? How?
- Undertook opening up works using a jackhammer
o Revealed double-skin brickwork with the steel joist embedded – no joist hangers or waterproofing present - Identified severely corroded steel with delamination
- Observed severe cracking above the steel on the asphalt roof covering, and through the parapet soldier course
- Identified slipped, missing and cracked ridge and roof tiles
- Cracking and blisters across each of the asphalt roof coverings
- Observed all defects via safe access from scaffold platforms
Can you describe delamination of steel joists? How did you establish this?
- Delamination – separation of layers of the steel joist due to corrosion
- Delaminated section was embedded into inner brick skin – I judged this to be very risky in respect of being structurally sound
- Internally, acro props had been installed behind plasterboard – opening up works revealed this
- Intrusive inspection revealed this
Why was a timber frame used over steel or traditional construction?
- Quick construction time
- Manufactured off site, quality control etc. no on site cutting or storage
- Lower embodied energy
How did you select the joists and centres for Roof 1?
- C24 is strongest and for external uses
- Checked stipulations in Approved Document A
- Centres – checked the NHBC guidelines which advises:
o Minimum centres of 450mm for 15mm deck
o Minimum centres 600mm for 18mm deck - Selected 400mm centres due to potential future loading of roof
- Checked all proposals / measurements with structural engineer before proceeding
What is the difference between C16 and C24?
- Used to grade softwood, under BS EN 338
- C24 can take a higher point load and has fewer, and smaller knots in the timber
- Timbers are evaluated after being kiln dried to 20% moisture content.
How were the joists supported?
- Installed timber wall plate bedded into mortar on top of the inner skin using galvanised holding-down straps using M10 steel bolts
- Joists installed onto joist hangers, fixed onto the wall plate using M10 steel bolts
How did the contractor carry out the joist & deck installation?
- Joists as above
- Deck embedded into brickwork and fixed onto joists using screw fixing of 53mm allowing embedding into joist of 35mm
- Minimum fastener edge distance 8mm
- Minimum bearing distance 18mm
- Panels fastened to joists at 300mm centres
What was the roof build-up?
- 48x220mm timber joists
- 70mm firings
- 18mm plywood deck
- VCL
- 120mm PIR insulation
- Underlay sheet
- Cap sheet