Does a geotechnical engineer report to council

[invamped]

Hello,

I have some potential subsidence issue on my home. I’m wanting to have a geotechnical engineer do a report to diagnose and tell me what’s causing it.

There nothing major showing just some hairline cracks in block work on each side of the house.

I’m think the house is built on reactive clay, as all the grass and gardens etc all have large cracks in them like I’ve never seen.

Question is. If I get an GT engineer to do a report and he says it soil issues will this be reported to council and noted on council documents LIM etc? Or do they only report it to me.

I just don’t want to make a mountain out of a mole hill etc.

Advance would be appreciated.

Thanks

[donna]

Hi invamped,

Welcome to the forums. I was reading there are different classes of reactive clay do you know what class yours is?

Other properties in the area are also probably getting the cracks as the moisture level drops - need to have the correct foundations for the class, so you're doing the right thing getting an engineer on to it.

The council would already know the soil type - however the class may not be known

Class A - site made up mostly of sand and rock with little or no ground movement with moisture changesClass S – site has slightly reactive clay that may experience some slight ground movement with a change in moisture levels
Class M – site is moderately reactive clay or silt with moderate ground movement from moisture changes
Class H1 – site has highly reactive clay which may experience high ground movement from moisture changes
Class H2 - site has highly reactive clay which may experience very high ground movement from moisture changes
Class E - site is extremely reactive which may experience extreme ground movement from moisture changes
Class P – soft or unstable sites due to soft clay, silt or loose sand, collapsing and eroded soils and sites that cannot be classified.

source

cheers,

Donna

[John the builder]

get a verbal report first and as Donna suggests what you have may be very normal and expected (and hairline cracks are normal). Ylou want to be informed not alarmed
Try and get a wise old engineer and not some spotty graduate just out of uni with no common sense

This has been a dry summer and expect expansive clays to be at their minimum volume?

[invamped]

Thanks for the replies, so getting a verbal report they wouldn't report their findings back to council?
If there are issues I want to avoid the council being notified until I know what to do about things.

any ideas?

[invamped]

Thanks Donna, where would I find this information? Property File? Its a 1970s built so I'm worried Ill purchase the file and it won't have much detail?

[John the builder]

the engineer works for you not the council Talk to them about confidentiality. They should give you assurance it is a common issue.

[Meehole]

A geotech engineer will write a report on samples of the soil taken advising, as Donna stated on what they find.
Some will advise a methodology to repair and some of the repair methods are money hungry and time consuming. Some can be OTT and show that the engineer has very little knowledge of what other methods are available.
It sounds like you have step cracking in your blocks caused by the clay shrinking, once it rains and the ground gets sodden they will probably close up.
I wouldn't recommend leaving them too long, as in 2 - 3 years because a stitch in time saves 9, as the saying goes.
Call a foundation repairer that specialises in underpinning and slabjacking. They might be able to save you a $5000 geotech bill.

[John the builder]

A geotech engineer will write a report on samples of the soil taken advising, as Donna stated on what they find.
Some will advise a methodology to repair and some of the repair methods are money hungry and time consuming. Some can be OTT and show that the engineer has very little knowledge of what other methods are available.
It sounds like you have step cracking in your blocks caused by the clay shrinking, once it rains and the ground gets sodden they will probably close up.
I wouldn't recommend leaving them too long, as in 2 - 3 years because a stitch in time saves 9, as the saying goes.
Call a foundation repairer that specialises in underpinning and slabjacking. They might be able to save you a $5000 geotech bill.

why would it get worse?

hairline cracking is not a sign of inherent defect?

[Meehole]

why would it get worse?

hairline cracking is not a sign of inherent defect?

Are you suggesting that the subsidence will fix itself and the gaps will close up without the intervention of an underpin or a slabjack?
What is a defect in your opinion John? Hairline or step cracking in bricks or blocks is often related to foundation issues, or am I wrong again?
If so then I should sell my business of fixing foundations.

[Learning]

They could be signs of settling. My parents house "settled" within the first couple years of being finished. One hairline crack in the kitchen and another in the entrance way. Neither have grown in the last 20 years.

[Meehole]

They could be signs of settling. My parents house "settled" within the first couple years of being finished. One hairline crack in the kitchen and another in the entrance way. Neither have grown in the last 20 years.

Our garage has quite a few hairline cracks after 2 years. We are in a flood plain and the soil is very wet so can only be expected. We compacted the ground to within an inch of its life but still got them.
We will eventually apply an epoxy resin to them which is noticeable but at least it plugs the gaps.

[John the builder]

Are you suggesting that the subsidence will fix itself and the gaps will close up without the intervention of an underpin or a slabjack?
What is a defect in your opinion John? Hairline or step cracking in bricks or blocks is often related to foundation issues, or am I wrong again?
If so then I should sell my business of fixing foundations.

Shrinking clay that then expands in winter is a normal occurance (and yes will cirrect itself). A properly designed foundation can allow for this if sufficient depth is attained for example) That is why Auckland foundations are 450-600 deep compared to other part NZ. 300?) or a rib-raft used to float on top of it all

A hairline crack is not a sign of subsidence and is expected in a rigid fabric, Step cracks means the movement is following the weaker joint in blocks?
This is not a defect (as such)

Subsidence means ground is being undermined or eroded or slumping what ever leaving foundation unsupported (permanently and getting progressively worse)

This is a defect when that happens. call meehole