Slab heave/ slab design/ engineering questions.....

Cracking everywhere · Feb 17, 2021 10:54 am

Hi all, I have a house that is less than one year old and is experiencing fairly serious slab heave. The builder of the house is denying any responsibility and this matter will most likely proceed to court.

Following my solicitors advice, I recently paid for an engineering inspection and report by the Managing Director of a fairly large engineering firm who's been in the game for close to 30 years. This report came back saying that the house has a slab that is designed for H2 classification soil and my soil classification is H2-D. This engineer says the slab as designed and built is non-compliant with AS2870 (which is referenced in the slab design notes) in several ways and will never perform properly into the future regardless of what rectification measures are employed. He says that there is no economical way to "stiffen" the slab and has recommended a full demolition and rebuild with an updated and code compliant slab design.

This all seems to have been a bit too easy as far as I'm concerned so before I sink a small fortune (that I really cannot afford) into pursuing this through the legal system, I have a few questions for the learned experts on this forum:

1. How likely is it that the new engineers calculations and analysis are correct? Is this a complicated analysis that is widely open to interpretation/ opinion or is it fairly black and white stuff for an experienced structural engineer?

2. Is it even possible that a large engineering firm (the one who designed my slab) signed off on and submitted plans for a slab that is not code compliant? How could that have happened? Aren't these things double and triple checked before being signed off?

3. Is it actually a legal requirement to design slabs that are in accordance with AS2870 or is it only "recommended"?

4. Why would council sign off on construction of a slab that is not code compliant?

Sorry for the silly questions but this is all new to me and I really don't know who or what to believe in all of this. Thank you for your advice.

StructuralBIMGuy · Feb 17, 2021 11:47 am

@Cracking everywhere
I would tend to back the 2nd engineer in.
All he needs to do is match the cracks with his Analysis/Data
while if you choose not to demolish you are left with a house not fit for purpose
I would recommend you lodge a complaint with the building commission, Unless your in NSW where there is no Building commission.
Hindsight is a wonderful thing and If you asked those questions before the slab pour you would have commissioned your own engineer chances are there was no one qualified on site during the pour
OT. as soon as you start seeing cracking. Buy yourself a Bosch GLL 3-80 CG Professional laser line level and start recording the slab movement. These will match the Investigating engineers Simulations.
Goodluck

Cracking everywhere · Feb 17, 2021 11:56 am

StructuralBIMGuy

@Cracking everywhere
I would tend to back the 2nd engineer in.
All he needs to do is match the cracks with his Analysis/Data
while if you choose not to demolish you are left with a house not fit for purpose
I would recommend you lodge a complaint with the building commission, Unless your in NSW where there is no Building commission.
Hindsight is a wonderful thing and If you asked those questions before the slab pour you would have commissioned your own engineer
chances are there was no one qualified on site during the pour
Goodluck

Thank you for the reply mate. He has drawn these conclusions by first inspecting the house and then looking over the slab design drawings which I provided him with. His conclusions weren't reached through monitoring of crack width etc. but more so analysing the drawings.

Yes, I wish I'd known more and been more involved when I started this build. In hindsight I feel very foolish and naïve but I just trusted that my builder knew what he was doing. Stupid right?

I do live indeed live in NSW.

Thanks again.

StructuralBIMGuy · Feb 17, 2021 12:29 pm

Its easy money to turn up and say the slab had to be upgraded and now pull it down after the event
Repairs and rectification work can only take place after movement has stopped
Severity of cracks is a function of movement/time & other factors which need to be measured
What you want to avoid is the legal costs and time delays and then wind up with a house that is repaired
My2c, a building commission would be more sympathetic to pulling down the build... the legal system not so.

Cracking everywhere · Feb 17, 2021 12:33 pm

StructuralBIMGuy

Its easy money to turn up and say the slab had to be upgraded and now pull it down after the event
Repairs and rectification work can only take place after movement has stopped
Severity of cracks is a function of movement/time & other factors
What you want to avoid is the legal costs and time delays and then wind up with a house that is repaired
My2c, a building commission would be more sympathetic to pulling down the build... the legal system not so.

Can a house with a non-compliant slab BE repaired?

How would that work? Wouldn't it continue to move no matter what repairs are carried out?

StructuralBIMGuy · Feb 17, 2021 1:13 pm

LOL most slabs I inspect for repairs are non compliant
Track down another engineer that does structural repairs, no harm in getting another opinion.
Lawyers tend to hire "pull it down" Engineers.. I tend to be the opposite in doing structural repairs
In the mean time monitor the movement/cracking to see if it's getting worse, stopped, etc, that is something that you can do, measure and log the data yourself If you choose to hire a surveyor it will cost you every time he comes back. I suggest you seek more advice locally
Cheers
Chris

Cracking everywhere · Feb 17, 2021 1:15 pm

StructuralBIMGuy

LOL most slabs I inspect for repairs are non compliant
Track down another engineer that does structural repairs, no harm in getting another opinion.
Lawyers tend to hire "pull it down" Engineers.. I tend to be the opposite in doing structural repairs
In the mean time monitor the movement/cracking to see if it's getting worse, stopped, etc, that is something that you can do, measure and log the data yourself If you choose to hire a surveyor it will cost you every time he comes back. I suggest you seek more advice locally
Cheers
Chris

Here is the chart showing how the slab is non-compliant. Sorry for asking so many questions but do you think this is something that could be worked with? Thank you again for your advice.

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StructuralBIMGuy · Feb 17, 2021 2:23 pm

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Here HTH
BTW the builder should have a copy of these codes

Harts · Feb 18, 2021 12:13 am

Sorry to hear you have slab heave and non compliant slab and great that you have come onto this site to increase your knowledge and many experts who have great expertise.

Apart from an Engineer inspecting and commenting on the slab non-compliance, have other investigations taken place?
What is causing the slab heave? Have the underground stormwater and sanitary pipes been checked with CCTV to see if there are broken pipes or water leakage?

I have had an ongoing battle for 8 years. The builder completed 'bandaid' fixing but it kept getting worse, he stopped communicating denying responsibility. I hired a lawyer. He also recommended an Engineer and investigations (including floor levels and crack width etc) and report provided. Recommendation knockdown and rebuild due to significant structural damage and floor levels 154mm out of level, caused by non compliance. Lawyer recommended VCAT and estimate cost of $140k - $230k. I spent $1000's with appointments, letters, phone calls etc with the lawyer and was pushing VCAT, saying it was my only option.
Because lawyer had sent letters to Builder, original Engineer and Geotech they all hired Engineers and they all came up with different causes deflecting blame from their 'party'.

I decided to do my own homework. Read everything I could get my hands on. Noticed differences in Engineering drawings to what was constructed and obvious plumbing non compliance from the knowledge I was gaining. I sacked the lawyer.

I hired a Forensic Plumbing company and wish I had done this 7 years earlier. Four plumbers with non compliance and significant non compliant underground plumbing. Stormwater pipe breakages that were fixed with silicon and then covered over, insufficient gradient, cracks and a broken sewer pipe.

I submitted complaints to VBA (regulator in Victoria) and waiting for information regarding their investigations and actions for those responsible. I won't hold my breath.

I am now out of my home as it is unsafe to live in due to significant structural damage. It will be demolished and rebuilt this year.

There are many stories on this site regarding slab heave. Have a read, knowledge is power.

Good luck

Cracking everywhere · Feb 18, 2021 10:43 pm

Harts

Sorry to hear you have slab heave and non compliant slab and great that you have come onto this site to increase your knowledge and many experts who have great expertise.

Apart from an Engineer inspecting and commenting on the slab non-compliance, have other investigations taken place?
What is causing the slab heave? Have the underground stormwater and sanitary pipes been checked with CCTV to see if there are broken pipes or water leakage?

I have had an ongoing battle for 8 years. The builder completed 'bandaid' fixing but it kept getting worse, he stopped communicating denying responsibility. I hired a lawyer. He also recommended an Engineer and investigations (including floor levels and crack width etc) and report provided. Recommendation knockdown and rebuild due to significant structural damage and floor levels 154mm out of level, caused by non compliance. Lawyer recommended VCAT and estimate cost of $140k - $230k. I spent $1000's with appointments, letters, phone calls etc with the lawyer and was pushing VCAT, saying it was my only option.
Because lawyer had sent letters to Builder, original Engineer and Geotech they all hired Engineers and they all came up with different causes deflecting blame from their 'party'.

I decided to do my own homework. Read everything I could get my hands on. Noticed differences in Engineering drawings to what was constructed and obvious plumbing non compliance from the knowledge I was gaining. I sacked the lawyer.

I hired a Forensic Plumbing company and wish I had done this 7 years earlier. Four plumbers with non compliance and significant non compliant underground plumbing. Stormwater pipe breakages that were fixed with silicon and then covered over, insufficient gradient, cracks and a broken sewer pipe.

I submitted complaints to VBA (regulator in Victoria) and waiting for information regarding their investigations and actions for those responsible. I won't hold my breath.

I am now out of my home as it is unsafe to live in due to significant structural damage. It will be demolished and rebuilt this year.

There are many stories on this site regarding slab heave. Have a read, knowledge is power.

Good luck

Thank you for the detailed response Harts.

Thus far I have had a building inspection and report, a full CCTV inspection of the plumbing (some of it is not code compliant) with accompanying written report and a structural engineers inspection and report that has found the slab is not compliant with AS2870- mainly because it's an H2 class slab and my soil is H2-D classification.

If you sacked your lawyer, how did you get this result at VCAT? Did you end up representing yourself?