Case study Flashcards
What was the use class of your building?
B2 - General Industrial
How did you determine the age of the building?
- The asbestos roof was a good indicator that the property was constructed in circa 1970s when these installations were most prevalent.
- I also reviewed the planning portal to see if there were any historic planning applications for the industrial estate which there were not.
How did you know that the warehouse floor was in-situ cast? How is an in situ concrete floor slab cast?
- There were day joints present to the concrete slab which indicated the different stages that it was cast.
- In this instance, the long strip method had been used whereby the floor had been cast in two long strips. The process involves laying the concrete between formwork which defines the strip and then levelling the surface manually using a compacting beam and following the top edge of the formwork.
What would be the build up of the slab?
Typically:
- Wearing surface.
- Structural slab.
- DPM membrane.
- Hardcore sub base.
- Formation level (earth) which may have been built up using sub-grade fill.
What type of asbestos would you expect to find in the cement roof sheets?
- Chrysotile - this was confirmed by the asbestos refurbishment and demolition survey I instructed.
Were there any other ACM’s picked up by the R&D survey?
Yes:
- Chrysotile located in the adhesive backing to the vinyl floor tiles at ground floor level.
- Chrysotile located in the sink pad to the kitchen / break out area.
What did you request from the contractor following the asbestos removal?
- A written confirmation that they had removed the asbestos as identified within the asbestos R&D survey.
- A consignment notice to prove the asbestos has been disposed of as hazardous waste (double bagged and then taken) which quoted the asbestos item codes from the R&D survey itself.
Where the asbestos works notifiable?
- No, as the works were sporadic and of low intensity and carried out in such a way that workers would not be exposed to levels of asbestos beyond the legal control limit of 0.6f/cm3.
- The principal designer requested an air control certificate to ensure that levels were not breached. This was also highlighted by the PD upon review of the contractor’s original Construction Phase Plan.
How much was the dilaps settlement? What was superseded?
- £90,000
- Decorations to the existing roller shutter door (to be replaced).
- Decorations to the portion of the ancillary accommodation block that was demolished.
What is a CAT A refurbishment?
- Also known as a developer’s fit out.
- Provides generic requirements for an incoming tenant such as life safety elements and basic fittings including suspended ceilings, raised floors, carpet and lighting.
- Absent of any tenant bespoke services and finishes.
Why was single stage competitive tendering used?
- Ensured that the tendered costs would be competitive and provide good value.
- Single stage tendering reduced the overall tender period compared to two stage and provided a lump sum cost for the works meaning the client could quickly determine the capital required for the project.
- The client was used to the method and had had success with it on previous projects.
Why did you use the JCT Intermediate Contract? Why didn’t you use with contractor’s design portion?
- The works were relatively simple in nature and involved recognised basic trades.
- The client required the works to be designed on their behalf by myself with the exception of the roof specification which was compiled by Tata Steel, the client approved of this.
- Additional provisions were required such as partial possession and more detailed extension of time provisions compared to that of the MW contract.
- More detailed provisions for loss and expence provided for.
- Provision for testing and opening up - may be needed particularly for roof works.
- They want the consultant to be responsible for all design so that there is a single point of liability should there be an issue with any elements of the design. It is also why all sub-consultants are appointed by Hollis and not directly by the client. We are responsible for everything.
- For example, at Leatherhead the roof oversheet was designed by Tata, but we will still be responsible from M&G’s perspective so we will have to rectify it in the event of faulty design.
What are the types of specification?
- Prescriptive specifications: Provide detailed descriptions of specific materials to use and how they should be installed.
- Performance specifications: Addresses the operational requirements of a installation. The focus is on the project outcome, indicating how it must function, it is up to the contractor how they achieve this.
- Descriptive specifications: Designer controls design intent and defines the performance criteria. Specialist contractor uses skills and expertise to complete the design whilst maintaining the design intent.
What was the build-up / specification of the new roof?
- The specification was provided by Tata Steel as I had specified their systems on other projects that had been a success.
- The system specified was the Tata Steel Trisobuild roof system.
- System comprised of external profiled metal cladding sheets, spacer system, thermal insulation layer and vapour control membrane.
Draw the build up of the new roof system.
- Include for VCL (always on warm side of insulation) and existing roof!
Describe the stages of decorating the profiled metal cladding
- Cladding will be cleaned using a jet wash to remove all grease, oil, general dirt and contaminates and existing flaking paintwork.
- All areas not to be painted will be masked off.
- All cladding will be brushed to remove any dust that could prevent adhesion.
- Spot priming will be undertaken to areas where there is bare metal resulting from the cleaning process to provide a mechanical key.
- Elevation then should be coated in an undercoat to ensure adhesion between the new topcoat and cladding.
- Apply the finishing / top coat.
What were the rooflights? What were their built up? What guarantee did they have?
- Trilite 30 GRP profiled roof lights consisting of inner and outer sheet separated by a polyethylene foam fillers to the internal void.
- Installed with 2 layers of sealant to end laps and one to each side lap.
- Service life in excess of 30 years, 25 year performance warranty from manufacturer.
Draw the rooflight
What u-value did the roof achieve?
0.18
What issues were noted in the CCTV drainage survey?
- Fractures to pipework in isolated locations.
- Silt and debris build up.
- Oil interceptor required maintenance.
- Cost came to £11,000.
How were the drainage repairs completed?
What did you specify for the movement joints?
Sika flex - a silane modified polymer sealant.
What paint was used on the portal frame?
- Crown Gloss metal paint.
- An intumescent paint had not been used as Part B does not require single storey portal frame buildings to have fire protection as they are not supporting any structure above. We would have needed intumescent paint if there was a roof plant area that had permanent access.
- I consulted the improved inspector on this to ensure that those steels that provide restraint to the party wall needed any further fire protection, he confirmed that the existing masonry would be sufficient.
- Note additionally, steels to part walls would need to have increased foundations to prevent uplifting if collapse of purlins occurred.
What testing did the contractor carry out for the retained services?
- Electrical Installation Condition Report.
- Tested the existing fire alarm installation.
How was the epoxy coating applied to the warehouse concrete floor slab?
- Preparation of concrete floor slab
- the concrete floor slab itself needs to be initially sound. Isolated repair screed any of these areas.
- Remove all existing laitance and previous surface treatments by using mechanical preparation which can be through diamond grinding or abrasive blast cleaning.
- Slab should then be cleaned and left to try so it is free of oil and any contaminates. - Priming
- Usually two coat application process does not require priming but exceptionally porous concrete may need a priming layer to ensure adhesion and left for 12 hours. - Application
- Roller apply the epoxy coating by hand and then apply second coat between 16-48 hours later.
- Need to ensure that the ambient temperature is kept at a minimum 15 degrees or this can affect the curing and the subsequent finish.
What is diamond grinding?
Diamond grinding is a highly efficient method used to restore concrete flooring or prepare it for a new floor coating. The process uses machines (known as diamond grinders) which have horizontally rotating discs with diamond-tipped saw blades. As the discs spin, these blades clean, level and restore the concrete surface.
What competencies did you utilise during this project and how?
What building regulations were applicable to your case study? How / what are they?
Approved Document L - Conservation of fuel and power
- I ensured that the minimum u-values were met by the new windows (0.16).
- I ensured that the minimum u-values were met by the new roof system (0.18).
- Lighting - Warehouse: 150 Lux (minimum required for rack storage - Logistics and Warehouses). Offices: 500 Lux (minimum required for writing, typing and reading - Offices).
Approved Document B - Fire safety
- Ensured that all fire doors onto the protected escape route had intumescent strips (all edges), smoke seals (all edges), door closers and fire door signage on both sides.
- Ensured that service penetrations were sealed with fire batt.
- Ensured that insulation was fire rated - LPCB approved to EXT 2.
- Ensured that escape distances were still compliant after demolition of the ancillary - Industrial = 45 in one direction and 25 in one.
Approved Document A - Structure
- Ensured that loading assessment was undertaken prior to installation of new oversheet system. Regs state that testing should be undertaken when change in roof loading is increased around 15%.
You mentioned that you used the JCT Intermediate Contract, why didn’t you use the contract with a contractor’s design portion?
The client wanted us as the design consultant to be responsible for all design work so that there was a single point of liability should there be any issues with the design.
Talk me through the construction of your property.
- Working from top to bottom:
- Steel portal frame.
- Asbestos cement roof sheets with single skinned GRP roof lights.
- Profiled metal cladding with plastisol coating.
- Low level masonry formed of a cavity wall construction as there is stretcher bond observed - assume to be no internal insulation with a cavity circa. 50mm (more modern cavity would be 100mm or wider).
- In-situ cast concrete floor forming the first floor of the ancillary accommodation.
- In-situ cast concrete floor slab.
- Foundations are assumed to be pad foundations to the columns, with either traditional strip foundations for low level masonry or concrete ground beams providing structural support for the low level masonry which span and distribute loads to the pad foundations.
What tender documentation did you issue as part of the works?
- NSB prelims and preambles and form of tender.
- Separate M&E specification prepared by engineers.
- Pricing document.
- Appendices: Pre-construction information (prepared by PD), Tata Steel roof oversheet specification, CCTV drainage survey, Asbestos R&D survey.
Why did you appoint an approved inspector?
- They are generally more responsive and open to giving advise that the local authority.
Why did you specify the Giromax Roofcoat for one of your options?
- I initially researched the various products on the market via web searches.
- I had reviewed the data sheet for the product and found that it could be applied to the roof sheets on the property.
- The product had a 20 year system guarantee which would ensure the roof would be covered for the duration of a successive 10-year lease term.
- I then spoke internally to colleagues who had utilised to same system and approved of its’ performance.
- I issued photographs from my initial inspection to a representative from Giromax for them to confirm that the roofsheets in their current condition would be suitable for the system.
- I then concluded from my research that the product could specified.
- Other products were considered e.g GLS asbestos roof coating system however they were far less responsive which I thought was important, particularly when it came to aftercare / warranty services.
What is the life expectancy of a asbestos cement roof sheets?
- 50 years although can last longer - the roof would have reached or been close to reaching this age.
Why didn’t the client want to grant a schedule of condition?
- Because this would limit their repair liability for the roof as if appended to a lease the tenant would likely only have to keep the roof in no better state of condition as evidenced by the schedule of condition meaning that the landlord may have to repair the roof at great cost come the end of the lease term.
What is the closed box system? How is it carried out? What material would you refer to?
Procedure
- Prevent slurry from entering the building from the cleaning process by sealing all gaps with polythene sheeting and duct tape.
- Only in exception circumstances is high-pressure jetting appropriate (requires specialist contractor)
- Cleaning machine is lowered down the sheets from the ridge. The process creates a lot of slurry so the contractor must prevent this from entering into the drainage system - attach a collection and filtration system that diverts the slurry from the rainwater goods to the filter system.
- Ensure that all rags etc used in the works are double bagged (asbestos bag then in clear ploythene bag).
- HSE offer task sheets that give guidance - task sheet A12.
- These works would be non-licensed.
What is the required U-value of the roof system? What u value did you achieve?
- Approved document L (conservation of fuel and power) states that thermal elements being renovated (the roof) will need to meet the ‘improved’ u-value of 0.18 (pitched roof with insulation at rafter level).
- Renovation of a thermal element = ‘providing a new layer through cladding’.
- If replacing over 50% of the surface of the thermal element, this counts renovation.
Why did you have to meet current building regulations with regards to the roof u value?
- Approved document L states:
- If a thermal element is renovated and one of the following applies, then the whole of the thermal element should be improved to achieve at least the U-value in Table 4.2 column (b). a. More than 50% of the surface of the individual thermal element is renovated (see paragraph 11.4). b. The work constitutes a major renovation. A major renovation is when more than 25% of the surface area of the external building envelope is renovated.
There is a railway track adjacent to your site, did this affect any of the works? What did you do to ensure nothing had to be done prior to the works being carried out?
- I enquired with Network Rail to determine whether this would be an issue at pre-contract stage. If the works were within 3 metres or to be undertaken to a network rail asset directly (such as an archway) I would need to have secured a BAPA agreement with NR (Basic Asset Protection Agreement). As the works were not within 3m this was not necessary.
- I did highlight in the pre-construction information that the railway line was present to make the contractor aware.
Why did you choose the JCT Intermediate Contract for the works ? Explain the thought process behind your decision.
- The works were relatively simple in nature - all basic trades without very complex building services installations.
- The client wanted Hollis to be responsible for all design so that there is a single point of liability should there be an issue with any elements of the design. It is also why all sub-consultants are appointed by Hollis and not directly by the client.
- Required additional provisions in such as partial possession and collateral warranties.
- Client had more experience administering the Intermediate Contract.
What design considerations did you consider for the oversheeting of the roof?
- Call Tata steel.
What design considerations need to be taken into account when designing a new roof / oversheet system?
What assessment did you undertake prior to the installation of the new roofing system?
- A loading assessment was instructed prior to tendering the works to determine whether the existing portal frame could safely accommodate the imposed load of the new roof safely.
- Prior to the assessment I instructed a measured survey to be undertaken of the entire property which would provide the structural engineer with existing drawings to undertake their assessment further to undertaking a physical inspection of the structure. Foundations were not surveyed as the increase in total load was less than 10%.
What are the different types of synthetic resin flooring for warehouses?
