Building Pathology (L3) - Withernsea Flashcards
What recommendations did you provide your client and why?
I advised the client to replace the floor slab including their sub-base.
How did you go about reinstating the new floor?
- I removed the existing walls built of the floor slab and then removed the existing floor and sub-base.
- I installed a new concrete floor slab with a physical DPM.
- I replaced the damaged bricks to the internal and external walls below DPC
- I erected new partition walls.
What was the new floor construction you proposed for your client?
- 150mm MOT Type 1 Roadstone
- 50mm sand blinding
- 1200-gauge damp-proof membrane
- 150mm Kingspan Kooltherm K3 PIR insulation
- Separation layer
- 150mm C30 concrete with 1 layer of A193 mesh with a minimum of 40mm cover
- Arditex NA Ultra Rapid Hardening Latex floor levelling compound
- Clients desired floor finish was carpet throughout and vinyl to the kitchen and bathroom
Why did you recommend a solid floor slab and not a suspended floor?
The existing footprint was already suitable and ready to receive a new concrete floor.
A suspended floor would require the introduction of ventilation which would extend the programme and increase the cost.
What were your findings following your inspection?
- I identified cracking to the floor slab in a map pattern.
- The floor centrally, was ‘domed’ and I confirmed this using a length a timber that was on-site.
- I identified cracking to the walls externally, below DPC level.
- I noticed the internal doors were also catching the floor and were not able to open fully.
Describe the dimensions/characteristics of the cracking?
The walls below DPC had been pushed outward by 3-4mm. I noted vertical cracking to the corner brickwork.
Did you carry any testing to confirm your diagnosis?
No. I felt in this instance, testing was not necessary. The floor undoubtedly required replacing and a test would only confirm what I already thought was the issue based on my findings.
If to be sure, I could have taken samples of the affected concrete for sulphate testing and petrographic examination.
How did you go about producing a budget estimate for the replacement of the floor slab?
I used a project which a fellow colleague had undertaken the previous year which was of a similar nature.
What is sulphate attack?
When sulphates become soluble they ingress into the concrete which a reaction occurs of sulphate ions with calcium hydroxide and calcium aluminate hydrate to form gypsum and ettringite which expand.
What is Petrographic testing?
Petrographic testing is the use of microscopes to examine samples of rock or concrete to determine their mineralogical and chemical characteristics.
