Seven year old home with the garage/basement slab cracked with 1/4 displacement. What would you indicate to buyers in your report about the crack. Front porch had a vertical settlement crack.
SEE PICTURES
I would refer it to a foundation expert or engineer but that is just me
House built on disturbed earth AKA “Fill” not compacted to 95% of dry density. 
A bit detailed Marcel. 
I’m going with:
It’s broke. Fix it.:shock:
Well, they asked;)
Mostly clay here Marcel it expands it expands and shrinks with a blink of a eye. Also a few sink holes around. It would safer to have it evaluated . But your likely right about it being not compacted
Usually here in my area the two most common causes is poor compaction as Marcel stated and clay soil swelling from moisture intrusion under the slab. If I were called to do an engineering investigation I would do the following:
1.) Check USDA published soil data for shrink/swell potential.
2.) See if surface grading and/or gutter system is dumping water near the foundation.
3.) Map the surface elevation of the slab to try and determine if the slab settled or was raised.
4.) Try to establish the timeline on when the crack formed. Did it take five or more years to go from a hairline crack to the current configuration or did it happen in only a few months.
Coring and sampling the soil under the slab is usually reserved for larger commercial slab failures, where the cost of the additional geotechnical work is small compared to the cost of repair.
Thanks Randy . As i said refer to a expert lol
Randy and Marcel, do ya’ll not think it may also have to do with a weak concrete PSI and / or inadequate steel reinforcemet in concrete of the slab? Looking at pic #3, I’ve never seen nothing around here like that one in south Texas where we also have expansive, shifting and rocky soils. That’s why we don’t do basements around here. We use the old floating slab foundation. I tell clients don’t worry about the concrete cracks in the foundaion til you can stick a quarter in it. Pic number 3 that Sam submitted I could stick my foot in that one. We are talking major structural issue here. Randy, wouldn’t the seperation of that excessive gap in pic 3 be more so due to a weak concrete pour and/or lack of proper steel reinforcement, where as improper soil and/or fill conditions would be evidenced more so by heaving at cracking in surface and or differential uplift on side(s) of crack(s) at this point after 7 years? The look of that concrete surface in pic 3 just doesn’t even look right !
Or built on a clay base with no ground protection for freezing. In any event call on an expert.
Oops!!! That would not apply however expansion can occur without freezing.
http://www.structuremag.org/OldArchives/2003/december_january/Mysterysoil.pdf
My thoughts, too, Marcel.
What kind of soils do mostly you have out there in Maine? We have mostly sand around here but a few pockets of various other soils.
Good point Joe, but even up here, you would be lucky to get or have a #10 wire mesh in the slab of the garage. Not quite adequate for expansive soils or settlement issues.
Geotech engineering firm and structural anylisis required by an Enginneering Firm for this one. Looks like they built on a steep slope area also. 
We have a variety of soils here Larry.
Mostly gravel sandy soils, ledge, rocky, clay and sandy soils near the coast.
Frost is the culprit up here, but slabs with radiant heating is proving very well.
Differential cracks in a slab like the OP tells me there is a major problem with the foundation base and material earth installation.
Learn something new. I thought the houses still had dirt floors in Tennessee.
Maybe they do, I did not ask Wayne about that. LOL:)
LOL just some newer ones , Slabs kept cracking
Quite frankly in that pic 3 the concrete looks like a concrete - mud combo. Doesn’t that count as a dirt floor 
? ?
It also looks like that concrete was poured super wet, almost to the point of being self leveling. That mottled surface pattern is typical when excess bleed water is bull floated back into the mix. As others have notice, Pic 3 does not have a clean break associated with good quality concrete.
Looks like 90% clay to me and not even concrete.:mrgreen: