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

Cracking everywhere · Feb 17, 2021 9:54 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 10:47 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 10:56 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 11:29 am

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 11:33 am

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 12:13 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 12:15 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 1:23 pm

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

Harts · Feb 17, 2021 11:13 pm

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 9:43 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?

MBX3 · Nov 16, 2021 8:22 am

Apologies if I am hijacking the thread but I believe all involved may be of some help to me

Our slab has now bee poured but I have found a discrepancy in the structural comps and structural plans used for the construction.

This is set of slab comps where design engineer has used 1N16 as bottom bars for calculating slab strengths. Yes comps show that the capacities surpasses the design forces, however these numbers are based on the wrong sized bars. Assumes that builder has used N16 for rib reinforcement.
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Below is the footing spec shown on the endorsed structural plans that builder used for ordering material and boxing up slab.
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Questions:

Am I within my rights to query the structural engineer that why they have used N16 for computations but then specified a smaller size N12 reinforcement bars in actual structural plans?
If this indeed was a stuff up from engineer, what are my options noting that the slab was just poured last week.
Can a Bobcat driving over the new slab that has only had 72hrs (3 days) of curing time a problem worth bringing to Engineer's attention? (mostly kept moist/wet by the horrible weather we had this month in Melbourne)

Background - Class P waffle pod slab, controlled filled site with level 1 certificate by developer but independent soil testing revealed some areas have <50kpa bearing capacity, Engineers adopted perimeter bored piers costing me $$$$ that I shouldn't have been paying for. No piers in the middle under internal load bearing walls for a single storey skillion roof trusses.

Any advice would be appreciated.

Mauromario · Nov 16, 2021 2:40 pm

Hi i may be bit late trying to help but your expert engineer is right,ive had the same but a lot more complex my slab actually spilt in 2 place we took it to vcat we knew we had the evidance we nedded unfortunately we got a lawyer that was in it for the money i thought boy was i wrong he was actually passing information onto the builder he was told to make our case go away, accoring to our files after we parted ways there was a lot charges but no proof from the barrister. Anyway our story is bit long but ill say this what ever a engineer disgns plans they have a hand shake with builder i can only speak for myself but if there's any indication looks like all volume builders do the same crap with slab heave there is no fix once your reo has been bent with heave there is no fix for it, piers are over used for the wrong reason, piers are great if you have large trees or had trees removed that piers will help that is to stop sourounding soil from shrinking affects so piers are just in place to hold ylur slab up. But if you have water getting into your soil or clay your soil will swell 3times that causes your slab heave to heave piers will not do anything unlessthey are tied into the top slab, so as it standsid take the word of your expert engineer if your not sure hire another expert engineer for a second opinion bare in mind more experts you have mofe confusing it gets for yourself trying to understand the legal side of things, our lawyer is a ex builder turned lawyer what he did for us in 9 months our first lawyer connot achive in 5 years. And his rates are not to bad. If you need a lawyer that is honest and truthfull, his name is Mark Croft legal 1300366119 call him ask himthe question you need to ask. Let me know the outcome good luck

building-expert · Nov 16, 2021 9:43 pm

What was your VCAT outcome? Did builder fix anything?

Mauromario · Nov 16, 2021 10:42 pm

Underpinning done and Agricultural pipe installed 800mm deep in to clay around the house, just waiting on the engineers report that we had done 12 on the after the works he did new floor levels, i know that underpinning part of the house it's going to allow the rest of the house to move they said it will work so I know the slab is still moving according to floor levels I've doing this long enough to understand to read floor level now. Soon as i get the report should this week or early next week I know what the answer will be he will not sign off on it since he was not the original engineer . I will give builder 2 choices and only 2 that is bulldoze and rebuild or buy us out at market value. Will see out come of report.