Tell me about slab foundations

[Fudge Nuggets 19242]

On 2/7/2022 at 5:15 PM, gyroprotagonist said:

i am sad there are no Fat Tony/Drank Blvd. posts on this thread.  

But i got nothing to add.  In Dallas but on pier and beam.  the bedrock is fairly shallow in my 'hood. 

Hata Proof have no slab.

[TwiceHorn 31653]

Couple of follow-up questions.  

We have seen a couple of houses with "transferable foundation warranties," that indicate that piers have been installed.  Fairly obviously, that warranty would extend only to the work actually done and not any further deterioration.  Should that be comforting?

Second, what about plumbing?  We looked at one that apparently blew up during snowmaggedon and had much of the plumbing replaced with PVC.  That gave me the willies, even though the plumbing was theoretically new.

I get that plumbing in a slab can be difficult to deal with, fundamentally.  Then again, the plumbing should be somewhat protected and supported by the slab.  How common are plumbing problems in slabs?

Finally, we have come across some newer homes, built in the last 10-20 years, on slabs.  Is there any reason to believe those slabs might be better designed or built than those in 40-50 year old homes?  Or would it be preferable to have seen it do whatever it's going to do over the past 40-50 years.

Edited February 25, 2022 by TwiceHorn

[TeeDubya 3362]

On 2/2/2022 at 9:15 PM, Gil Bang said:

* i don't know shit about Texas slabs, but I've seen my share of foundation issues out here.

** post-tension slabs are the way to go 

Absolutely.

11 hours ago, TwiceHorn said:

Couple of follow-up questions.  

We have seen a couple of houses with "transferable foundation warranties," that indicate that piers have been installed.  Fairly obviously, that warranty would extend only to the work actually done and not any further deterioration.  Should that be comforting?

Second, what about plumbing?  We looked at one that apparently blew up during snowmaggedon and had much of the plumbing replaced with PVC.  That gave me the willies, even though the plumbing was theoretically new.

I get that plumbing in a slab can be difficult to deal with, fundamentally.  Then again, the plumbing should be somewhat protected and supported by the slab.  How common are plumbing problems in slabs?

Finally, we have come across some newer homes, built in the last 10-20 years, on slabs.  Is there any reason to believe those slabs might be better designed or built than those in 40-50 year old homes?  Or would it be preferable to have seen it do whatever it's going to do over the past 40-50 years.

Post-tensioned slab?  No problems, no worries.  PTS started in this part of the country in widespread use in the 70s.  
If you're on rock or really sandy soil, you normally won't see much contraction/expansion and non-PTS are often ok.  Clay expands and contracts with moisture content and temperature too.  PTS is a must.  

There are usually only one or two companies who do the PTS in an area, and they should have records of your slab, or even point you to another company if they didn't do yours....  

PVC done correctly is fine, as is Pex.  But, there can be problems from poor installation, and there can be issues with a certain group of Pex connectors made around 2010. 

And whomever said above about the noise when one snaps is right.  Around here, in home construction, they slab company will clear everyone out when they crank the tension up on the slabs when installing.  When the pop, it's like a arrestor cable on an aircraft carrier breaking.  It's loud and dangerous.

[TwiceHorn 31653]

I basically consider a slab foundation in Dallas to be engineering malpractice, mitigated only by cost constraints.

I won't know if it's post-tensioned until the inspection.  I guess I can just bail then if it's not.

[TwiceHorn 31653]

Got damn.  The house in question was listed for 659 and sold for 831k.

Fuck that right in the ass.

[Parliament 14357]

Has anyone advised OP to just dig a basement?

[deadshank 24653]

2 hours ago, Parliament said:

Has anyone advised OP to just dig a basement?

For the bodies?

[South Austin 52673]

14 hours ago, Parliament said:

Has anyone advised OP to just dig a basement?

It worked for the Alamo.

[TwiceHorn 31653]

An academic follow-on question.

We have seen a couple of houses that were pier and beam but enclosed an attached garage at some point, and the garage, I believe, was slab.

Most garages on slabs are cracked all to shit, if they're at all old.  We have seen one where the garage slab was "reinforced" with piers.  Others, not clear at all.

Usually, enclosed garages are janky as shit, but we have seen a couple where it wasn't even that obvious (and a few where it stuck out like a sore thumb).  

Anyway, it seems like a slab garage enclosed and "interior sheetrocked" to the rest of the house is just a disaster waiting to happen in terms of settling at a different rate and generalized cracking.

True or false?

[fattyflattie 4639]

3 hours ago, TwiceHorn said:

Anyway, it seems like a slab garage enclosed and "interior sheetrocked" to the rest of the house is just a disaster waiting to happen in terms of settling at a different rate and generalized cracking.

True or false?

I’d vote false.  It wouldn’t surprise me though if the garage was an “addition”, that there could be some short cutting or cost saving in the slab, that could cause issues. Around Houston, anyhow, it seems they started finishing garages in the early 2000’s (at least in tract homes). Everyone I know with a tract home from that time forward has a finished garage. I know several from the mid 90’s (nice houses, ~4500ft^2) that don’t. Also, every detached garage I can think of that’s from that time, aren’t finished. The newer tract and customs I’ve been in with detached are all finished, and many climate controlled.  
 

All anecdotal in greater Houston area. 

[TwiceHorn 31653]

So, wound up buying a house with a slab foundation.  It had been freshly repainted, ostensibly because it was a darker color (to white for selling/showing purposes).  There wasn't much/any evidence of settling, but there were some cracks on the exterior brick, one fairly major where the garage started.  House is 44 years old.

So, had it examined and was recommended 33 piers around three sides.  Sellers agreed to cover it plus a discount for cosmetic repairs and an escrow in case any pipes broke.  

Was fascinating to watch, they just used bottle jacks then concrete blocks and steel shims.  All the doorframes were level using a carpenter's level and the floors within 0.25 over longer runs.  The piers hit some rock at about six feet, so there's pretty good confidence on the permanence of the repair.

A few interior cracks and taping buckling from the fresh paint job, but within the "allowance" we got for cosmetic repairs. An hydrostatic test revealed no plumbing leaks and the slab piping is PVC, so hopefully that's all good.

[Catpfish 618]

I'm willing to be that there was plenty of evidence of settling if it required 33 piers.  The painting more than likely included trying to fix the sheetrock cracks at the windows and doors.  I'm also willing to bet that the doors didn't stay open in place and moved around after positioning.  I'm glad it worked out, but that just screams of the sellers trying to get by while also being prepared to pony up if caught.  

[Armybrat 40945]

2 hours ago, TwiceHorn said:

So, wound up buying a house with a slab foundation.  It had been freshly repainted, ostensibly because it was a darker color (to white for selling/showing purposes).  There wasn't much/any evidence of settling, but there were some cracks on the exterior brick, one fairly major where the garage started.  House is 44 years old.

So, had it examined and was recommended 33 piers around three sides.  Sellers agreed to cover it plus a discount for cosmetic repairs and an escrow in case any pipes broke.  

Was fascinating to watch, they just used bottle jacks then concrete blocks and steel shims.  All the doorframes were level using a carpenter's level and the floors within 0.25 over longer runs.  The piers hit some rock at about six feet, so there's pretty good confidence on the permanence of the repair.

A few interior cracks and taping buckling from the fresh paint job, but within the "allowance" we got for cosmetic repairs. An hydrostatic test revealed no plumbing leaks and the slab piping is PVC, so hopefully that's all good.

What was the approximate cost of that work, if I may ask?

Yesterday we discovered a water leak outside that is apparently coming from under the slab at a corner of the house. Really soggy there and a small puddle has been collecting between some surface roots of the oak tree about 15’ away. 
I noticed the puddle several weeks ago, but thought it was from a recent rain. Son saw it over the weekend, and since it hasn’t rained recently, we investigated and discovered the mushy ground by that part of the foundation.

A leak detection service is coming by today with their specialized equipment. They charge $475 for the first hour. 
 

Houses in our area are prone to settling over the years because of the weird soil types, plus alternating droughts & extra wet seasons.
We had no problems for the first 15 years after we moved in this new build in 1995, but then went through several years of severe drought followed by some extra wet seasons. Then another severe drought for the past 6 months.
During the droughts I tried to keep the soil close to the foundation watered regularly as regulations permitted. 
16 years ago we had most of our living areas inside tiled in ceramic tiles. They did fine for about 8 years, then after several years of drought, a few developed hairline cracks. Son replaced a half dozen 4 years ago, but since then they cracked again - all hairline cracks - along with another dozen tiles around the living & dining rooms. 
And now this water leak outside, which may be related. But also the medium size oak tree (planted in 1995) in that part of the front yard might be the cause with its expanding root system.
We anticipate this will easily be running into the multiple thousands.

The next door neighbor on the other side of the house just finished having a similar problem resolved with a leak under the front part of his house. It took the plumbers a about three days of work with on & off digging in that one spot stretching over a week before they finished. Don’t know what their exact problem & costs were, as we have never met that neighbor (renters) since they moved in just before the pandemic started.

Edited March 27, 2023 by Armybrat

[TwiceHorn 31653]

3 hours ago, Catpfish said:

I'm willing to be that there was plenty of evidence of settling if it required 33 piers.  The painting more than likely included trying to fix the sheetrock cracks at the windows and doors.  I'm also willing to bet that the doors didn't stay open in place and moved around after positioning.  I'm glad it worked out, but that just screams of the sellers trying to get by while also being prepared to pony up if caught.  

Well, a lot of shit went wonky that way after the raise.  It had been reno'd some time ago and things were fixed.  So yeah they had some kind of clue, but their realtors said it was painted on their advice..

ETA:  I say "a lot," it's really not all that much.  A few of the doors are sticky, a half-dozen  cracks and bucklings and a couple of door moldings. Could have been a lot worse.  Tile floors intact.

Edited March 27, 2023 by TwiceHorn

[TwiceHorn 31653]

1 hour ago, Armybrat said:

What was the approximate cost of that work, if I may ask?

Yesterday we discovered a water leak outside that is apparently coming from under the slab at a corner of the house. Really soggy there and a small puddle has been collecting between some surface roots of the oak tree about 15’ away. 
I noticed the puddle several weeks ago, but thought it was from a recent rain. Son saw it over the weekend, and since it hasn’t rained recently, we investigated and discovered the mushy ground by that part of the foundation.

A leak detection service is coming by today with their specialized equipment. They charge $475 for the first hour. 
 

Houses in our area are prone to settling over the years because of the weird soil types, plus alternating droughts & extra wet seasons.
We had no problems for the first 15 years after we moved in this new build in 1995, but then went through several years of severe drought followed by some extra wet seasons. Then another severe drought for the past 6 months.
During the droughts I tried to keep the soil close to the foundation watered regularly as regulations permitted. 
16 years ago we had most of our living areas inside tiled in ceramic tiles. They did fine for about 8 years, then after several years of drought, a few developed hairline cracks. Son replaced a half dozen 4 years ago, but since then they cracked again - all hairline cracks - along with another dozen tiles around the living & dining rooms. 
And now this water leak outside, which may be related. But also the medium size oak tree (planted in 1995) in that part of the front yard might be the cause with its expanding root system.
We anticipate this will easily be running into the multiple thousands.

The next door neighbor on the other side of the house just finished having a similar problem resolved with a leak under the front part of his house. It took the plumbers a about three days of work with on & off digging in that one spot stretching over a week before they finished. Don’t know what their exact problem & costs were, as we have never met that neighbor (renters) since they moved in just before the pandemic started.

$13,200 for the foundation.

$300 for the leak test.

In the vicinity of $1000 for the cosmetic work.

Edited March 27, 2023 by TwiceHorn

[CooterBrown 18039]

What was the approximate cost of that work, if I may ask?

When I fixed a foundation about around ‘10, it was $450 a pier + $700 for engineering. Had to install 59 piers. It did come with a transferable lifetime warranty, which I would consider necessary for resale.