Any structural engineer peeps here ?

[thedoc46]

So had this weird event happen in my home yesterday.

Some kind of pressure event occurred and well its literally punched a hole up from the concrete slab, smashing thru some ceramic tiles and cracking a bunch of surrounding tiles, making another load hollow.

Home was constructed in 2009. I spoke to the builder who says (hopefully covering this under warranty) oh its just ground pressure from all the rain we've had recently ??????

Thing is, yes, we've had a more rain than on record, for the month of Jan, which typically only receives 4cm of rain in Jan... HOWEVER, I live in SW Florida, which has a rainy season, during June, July, Aug and Sept, and those months receive a good 25cm of rain if not more... So i'm finding hard to swallow that its rain in January that's just caused this.

Also though i've not fully ruled it out a cracked pipe, surely would be producing moisture or a smell (example cracked sewer pipe) I've covered the floor with plastic, as a way to see if any moisture is rising.. I've not removed the tiles yet, until a specialist looks at it. No moisture has presented itself as of yet.

Anyway a pic says a thousand words.

 

[thedoc46]

Sinkhole probably.

A sinkhole would have created a cave in, would be my guess, not an upward pressure. Besides sinkholes are a rare occurrence where I'm at.. A common occurrence about 200miles north mind, so cant rule anything out !

 

[thedoc46]

http://www.designingbuildings.co.uk/wiki/Ground_heave

Not an engineer, but in the architecture side of things. Sounds like ground heave / soil heave.

yikes.. Definitely seems to fall in line with the water table rising. We did get a a near 25cm of water dump down in the space of two days.

Question is what does the future hold for my home now? is this a one off unlikely occurrence or will this home be problematic from here onwards, affecting the resale value.

 

[thedoc46]

I'm an engineering geologist.

Is your house built on made ground or natural ground? There are various minerals in engineering fills that can expand when they oxidise or take on water.

Concrete can also expand due to 'aggressive' ground conditions due to sulphates (sulfates in American) or unsuitable aggregates used when mixing it in the first place.

In the UK a 2009 house would be under a 10 year warranty. Is something like that in effect where you live?

Various other things can also cause heave but I'd rather not speculate on the causes.

Yes I'm already in touch with the builder, who's trying to downplay it somewhat, saying its a common occurrence, and all the recent rain would have caused excessive ground pressure, and then they've gone on to say its not a structural issue but is a nuisance to deal with the cracked tiles. ??????? But he's just the warranty guy who i've dealt with in the past. He's not a structural or civil engineer.

I live in Naples SW Florida, which was all originally swamp lands and sand. I don't really have a clue about what i'm talking about here, but on the new construction sites i've been into, they seem like they compact mud / sand, then they lay the concrete slab. So i guess that's made ground ? But everything is subjected to a civil engineer and there should be records of the geo-technical engineering firm used. So i could get in touch with them for more info.

My biggest worry is this being a continued problem, rather than a one off ! and to make it a one off, what is involved ? completely redoing the concrete slab ? I can't imagine that's a simple procedure.

Here's a pic of my community under construction.

 

[thedoc46]

I spoke to a structural engineer, and he seemed to think it was most probably nothing more than thermal expansion of the slab, due to going from ground going from dry to wet. Seems fairly random. He said pull the tiles, and unless there's a huge crack in the slab, don't worry too much just re-tile and job done.. If there's a large crack in the slab, then call him and he'll come out for an inspection.

Best not jump for joy til the fat lady sings just yet, not pulled the tile, but at least its fairly promising news.

 

[thedoc46]

Doesn't Florida have an extensive aquifer network? could be ground movement due to that with the weather though seems unlikely they'd build where it was really prone to that.

More central than where I'm at... Underwater caves and sink holes are a problem up central FL

 

[thedoc46]

Was your engineer contact recommended to you by the builder! I'm no slab designer but I would assume an allowance is made for thermal expansions with gaps or sealed flexible joint if it is prevalent to such extent.

No i randomly used someone.

 

[thedoc46]

Weird things do happen tho. I once had a nice glass table, that was expensive & actually purchased in England and bought over to the USA when i originally moved here. One day sitting in my living room I heard an almighty explosion. I thought a car had somehow crashed into the front of my house or something. All it was, was the damn glass table exploding into a million pieces, for no apparent reason either.

I guess that was thermal expansion also.