I am new to to the discussion forum but have been a reader/subscriber for years. I am an Electrical Engineer (Enterprise Computer Storage Manufacturing) and an avid DIY. During college I worked with a Contractor revevating houses (Part Time) and have taken on some fairly expensive projects both Electrical and Construction over the years.
My current project is a ~1,300 sq Ft addition to my house (Typical New England Colonial). 24X24 above existing garage and ~12X48 Workshop/Mudroom/Sunroom off the back of the house. The WS/MR/SR is on a new foundation and slab on grade. The WS/MR use the slab as the floor and the SR is at the same level as the existing first floor (3 steps up from the MR).
Problem is the slab settled ~3″ tapering from the middle of the MR to the center of the WS. My plans were for Tile in the MR but now I am concerned about further settling and correcting/leveling the floor.
Possibilities include:
– Leveling Floor in MR using floor leverer and covering with ? I can live with the WS floor.
– Slab Jacking – Can’t seem to find anyone in my area who does this.
– Tear out and replace – Rather not…
Any suggestions?
Edited 4/27/2005 8:08 am ET by tool_man
Replies
What kind of subgrade do you have (sand, clay, boulders, etc.)? How did you prepare the subgrade? How long did it take from the time you finished the slab till you noticed it settled 3 inches? Are there any cracks or has the entire slab settled in one piece? Is the slab attached to the existing foundation or is there an expansion joint? Did it occur after a series of freeze-thaw cycles? That's for starters. I may have more questions after you answer these.
Ben,
The pit was fully excavated down to undisturbed soil and the footings rest on that soil. The foundation walls extend ~5ft below grade. The whole area inside the foundation was excavated and back filled with "hard pack" gravel. The gravel was compacted with the bucket of the excavator and a walk behind compactor (althought it was not done in layers).
The slab was poured in the early June 2004 and I noticed the settling late Jan/Feb 2005. So yes it occurred after freeze/thaw cycles.
There is one crack the runs from the left of the doorway opening toward the slider on a 30/45 angle. The rest of the settling was along a relief line in the workshop.
The slab is not attached to the foundation other than in the doorway area's where it sits on top of the door way openings.
Thanks Frank
I saw this thread/ topic somewhere else today. Now I can't find it. Hmmm."The whole area inside the foundation was excavated and back filled with "hard pack" gravel. The gravel was compacted with the bucket of the excavator and a walk behind compactor (althought it was not done in layers)."What is in the parentheses is the cause. The fill is NOT hard pack UNLESS it is done in lifts. What you have is the result of settling and it will continue. I think you read my earlier post. I like the concrete beam as stated in another post.Why can't I find that thread? Parellel universes? Hmmm...Frankie
Being new to this I posted in 2 places by accident. One thread is under General discussion and one is in Building techniques. You have to select show all to see them both...
Tool,
Are you sure that the contractor didn't sope your slab by mistake, thinking that the large opening was gonna be a garage door?
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
[email protected]
I've understood that gravel does not need to be done in lifts.
Am I being misled?
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
[email protected]
Tool_man stated:"The pit was fully excavated down to undisturbed soil and the footings rest on that soil. The foundation walls extend ~5ft below grade. The whole area inside the foundation was excavated and back filled with "hard pack" gravel. "I have NEVER seen ANYTHING* filled with 5' of gravel, let alone an area that big. So I assumed it was filled in with backfill (whatever was initially there) and then topped off with 6" of gravel. My error? HA!Anyways, whenever I have seen gravel used it was always tamped down somehow and when greater than 6" it was done in lifts.I am scratching my head now - Isn't slab on 5' of any type of backfill pretty foolish? There WILL be settling, esp when there is a high water table. Structural concrete beams would have been prudent. They could have been formed in the backfill and the wood forms allowed to remain.*Correction: Last Spring, I saw a 4' dia. swail pipe, which was about to be washed away as the road had flooded, get a few dumptrucks full of gravel (about the size of cobblestones and bigger) placed around it to hold it and the road in place. No need to tamp that down!Frankie
Edited 4/27/2005 5:49 pm ET by Frankie
I built a garage for an Archi about 3 years ago.
It was on a hillside and he filled the inside of the foundation with gravel all the way up to the high side where you would drive in. I'm talking 13ft high!
All they did was run the tamper around it before pouring the slab.
He said something about the friction between the pieces of gravel.........they lock themselves in place?
Seems I've read similiar here too.
I'm not defending it, just trying to learn something.
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
[email protected]
Holy Cow! There's still so much I don't know. Go figure!F
wow, It has been awhile since I have sen this much confusion in one thread.starting with the fact that this original poster (OP) used all kinds of abreviations to talk about several different rooms and additions to leave me reading it tjhree times to try to figure out what all those cap letter were refering to ...THEN HE SAID THAT THIS WAS A SLAB ON GRADE, BUT THAT HE EXCAVATED FIVE FEET DOWN TO SET FOOTINGS! I've never done a slab on grade that way. I pour a monolithic slab on grade. If I dig down and do stem walls on a footing it is now on a stem wall, not on grade.Then frankie says he has never seen anyone excavate that much and fill it back with gravel. That is the only way I have ever done any interior supporting fill. And other soil i slikely to hold moisture and resist compaction, gauranteeing that it will settle later.
The largest I can remember doing was a 28' octogonal structure, five feet deep. We filled with inch minus and had the compactor running around the clock while a bucket loader brought in the gravel. It kept up to the equivalent of four inch lifts but we would never lift more than a foot at a time with 8" being more typical.There was a reason I adressed this to you specifically in this thread, rather than the OP. What was it now???? I guess because you had never heard of compacting in lifts. Anyway, that is certainly the reason the OP had a problem. The slab didn't fail, the fluff fell out from under him.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Oh bother...........
Oh yes I am very familiar with compacting in lifts. Probably learned more about it here than I ever knew. My eyes and ears are wide open!
I do seem to remember some discussion here about using gravel for fill and that it did not need to be compacted. The architect seemed to think it was ok? He's designed and built several public transportation structures so i would only assume that he knows something. Maybe I didn't get the story right.
As I stated to Frankie, I am not defending the practice, just trying to learn.
I also stated to the OP that apparently there were problems with the fill beneath his slab. Yeah, he was spoutin' all kind of terms, but I think I figured out what he was doing after viewing the photo for a while. SR=sunroom, MR-mudroom, WS=workshop.
Crawl space to the left with sun room over, level to the existing floor of the structure, step down to the mudroom workshop on the right. That's where he had the problem.
He did not do a slab on grade as is obviously apparent in the photo. Or even stem walls.
He said they have a high clay soil.
I suggested that it may have dried out and shrank thus causing his settling. Am I having another fantasy? i understand clay shrinks and expands with the introduction or the lack of moisture, is that correct?
What was it now???? I guess because you had never heard of compacting in lifts.
Not sure how you arrived at that conclusion, but I do know that people sometimes think that they are reading things here that they are not. I can only assume that this is one of those occassions. Unless you can point out to me where I stated to anyone in this thread that compacting in lifts was not a recommended practice.
Shees Paul, having a bad day?
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
[email protected]
No - I wasn't picking on you. Sorry iof it seemed so. I had to reply somehwere in all this mess. I guess it was frankie who hadn't heard of something.Anyway - I feel sorry for your archy. I don't believe that friction will resist the void he'll have from soil settlement.But I have a little more confusion now - you mentioned a photo, but I can't remember seeing one in this thread. Then you report, "He said they have a high clay soil." but I read him to say that he had backfilled with hard packed gravel, even tho he was wrong and it was not hard packed since it wasn't done in lifts. The mention of clay was someone asking OP what soils he had.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Allright,
I'll take 1/2 the blame..........the OP had started another thread earlier, my response to you and some of the conversation I had with Frankie was a continuation of his earlier thread which did include a picture.
Forget it, I didn't have such a great day as you can see by my post times!
Re: the gravel thing though.....
Anyway - I feel sorry for your archy. I don't believe that friction will resist the void he'll have from soil settlement.
Here we go, I said gravel, you said soil.
You don't recall any discussion about this; using gravel as fill and not having to compact it? It was probably one of those heated threads I guess.
Think about it though, gravel doesn't settle, moisture will not diminsh it's volume or cause it to settle or collapse.
I'll have to check up on this one.
I'll go look for the other thread.
Regards,
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
[email protected]
Gravel will definitely settle. I see it all the time, and cause it by using a compactor.but when I said soil, I use that as a generic term that would include gravel. I still feel sorry for that archy - and for anyone he builds for with specs like that. Let me edit the statement from " I don't believe that friction will resist the void he'll have from soil settlement." to " I don't believe that friction will resist the void he'll have from gravel settlement."Thanks for the link, I think.
After chasing it down and waiting ten minutes for the photo to download, I'm more confused now. Maybe someone can tell me if I left half my brain laying around someplace, but this one is making me feel downright stupid. He said pretty clearly that he is finishing the job up, but from that phot, he is barely getting started. I'm trying to think of the right solution for him, and it would vary according to whether he already has a structure over this thing or not.Then in the phot, I don't see any slab at all. If there is one, he's got it pretty well disguised with gravel. If it is al open with no walls built yet, I'd go along with the idea of digging it back out again, and compacting it. I see where he siad in that thread that he has wet clay soils and it is obvious that his contractor knew that and that's why he refilled with gravel, but he apparantely didn't know about compacting.The design of the details on this strikes me as very odd, with part crawlspace and part slab, but all foundation stem walls same height. I'm trying to get my head around this thing and the more I try, the more tangled it gets...
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
How 'bout a little help here? If you poured on infill material with this slab, after excavating to undisturbed soil at five feet, then you understood the principle of compaction and load bearing. I see that your problem is caused by the fact that the infill has settled because it was not compacted properly. The question of what now to do about it depends on all the details though. Why did the slab not set on a bricklip type ledge in the stemwall? What exactly does the exterior load bearing exterior wall set on? If a 4" framed wall resides on an 8" stemwall, then you must have a step where the slab has settled below that, right?
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Here's the original thread.
http://forums.taunton.com/tp-breaktime/messages?msg=57521.1
Prospero shouldn't let newbies do this to us old guys, gets us all confoosed!
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
[email protected]