# Underpin??



## Tom R (Jun 1, 2004)

Okay, - - here's the problem, - - it's at my own house, - - built about 1905, but 'moved' about 40 years ago. I've got a 7' X 18' screened-in front porch, CMU w/slab, then columns and existing hip-roof. I want to incorporate 'it' as part of my living room, - - build-n-close it first, - - then blow out the existing front wall after I'm weathered-in. Trouble is, local code is 3' deep on the footers, - - I just dug out a section, - - existing is only 18" deep, - - I've got to get it to code before I can start framin'-n-all.

Need to start like yesterday, - - Mrs. tommer's already out furniture shoppin!! :cheesygri 

Not somethin' I've ever had to do before, - - but I'm guessin' I would first trench 'alongside' all the way around, - - then underpin by diggin'-n-fillin' w/solid concrete in 2 phases (every other section) so I don't lose my support in the meantime??

Wide open for criticism and/or suggestions of how to do this right, - - maybe even efficient.

Thanks.


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## jmic (Dec 10, 2005)

Hey Tom,
In Ct. we're 42" for frost, but I guess being south of us it could change to 36". Anyways what kind of soil do you have there? If it were hardpan you might be able to dig along side, then undermine it maybe 5" so you still have some bearing. Then form the outside and maybe pour a 10" wall around it. I'de say with hardpan you could at least do the two ends, and then once thats set up you could do the third side. If you have sandy conditions lets go back to the drawing board.
Joe


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## jmic (Dec 10, 2005)

Basiclly what you said isn't it? :biggrin:


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## Tom R (Jun 1, 2004)

jmic said:


> Basiclly what you said isn't it? :biggrin:


Sort of, - - but then I'm just throwin' my best guess out there, - - like I say, never done it before, so I appreciate the input.

Now, back to the facts, - - yep, 'sandy' soil, - - and yeah, - - here in Jersey our code is definitely 36" for the depth.


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## jmic (Dec 10, 2005)

Tom,
I'de still try plan "A" might work fine. You'll know when you start digging if the sand starts pouring down like sand in an hour glass then hold up. Grab a Rolling Rock and think it out some more. :thumbsup:
Joe


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## Tom R (Jun 1, 2004)

Yeah, - - it's not quite that sandy, - - just enough for the rolling rock, though!! :cheesygri


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## Tom R (Jun 1, 2004)

Thanks for the help, jmic, - - I appreciate it.

Actually, - - although it's only 18" deep and been there about 40 years, - - it hardly even has any cracks in it, - - just a spot or two where the stucco came loose, - - wonder if they'd allow me to underpin it 'pier' style?? Anyone else familiar with this sort of project??

Because there was no cracking/movement over all this time, - - I actually thought it was going to be real close to the 36", until I dug alongside today and checked it.


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## jmic (Dec 10, 2005)

Tom,
I would guess because you are changing uses they wouldn't allow that, but hey stranger things have happened!
Joe


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## mdshunk (Mar 13, 2005)

How about underpinning a short section with some real dirty concrete, leave it exposed, and then show the inspector that the existing conditions are already 36". :cheesygri


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## Tom R (Jun 1, 2004)

You're prob'ly right, - - I just hate to spend too much time/money re-inforcin' somethin' that ain't budged in 40 years.


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## Tom R (Jun 1, 2004)

mdshunk said:


> How about underpinning a short section with some real dirty concrete, leave it exposed, and then show the inspector that the existing conditions are already 36". :cheesygri


Actually, md, - - that was one of the first devious thoughts that crossed my mind also, - - but bein' kind of a glutton for punishment, - - I don't really mind doin' it right. Nothin' really worse than insultin' the guy's intelligence. 

Although, on that note, - - I did work with a guy once who successfully re-riveted the clip of his measurin' tape to make a 9' side-setback measurement appear to be 10' for a handicap ramp, - - when the inspector asked for a measurement he handed him the tape, - - holdin' on to the clip end, - - voila, - - 10' is what you want, - - 10' is what you get!! :thumbup:


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## Tom R (Jun 1, 2004)

Local inspection office is shut down this week, - - shame, - - I even showed up with my favorite cryin' towel, - - so no one to even ask how they want it done, - - plus the the tommer-lady ain't too happy there'll be a dumpster in the yard for the second Christmas in a row, - - no problem, - - I told her I'll get one that's red-n-green :cheesygri 

Anyway, - - best idea I've come up with so far is 6 maual piers, - - then a few days later dig-n-fill the rest solid.

Must be somebody out there who's run into this before, - - wonder if this is too small for Mike Sewell to be familiar with.


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## Tom R (Jun 1, 2004)

Bumpety-bump!!

Can't believe nobody's run into this situation before, - - besides me, that is. :cheesygri


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## jmic (Dec 10, 2005)

Tom,
I can't believe your bldg. dept is closed for the week, wow! Do you live in a small town that share's inspector with other town's?
Joe


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## Nick H (Nov 13, 2005)

Tom R said:


> Bumpety-bump!!
> 
> Can't believe nobody's run into this situation before, - - besides me, that is. :cheesygri


The way we usually do it over here is to dig out alternate 6' sections then dig out underneath the existing founds and concrete to within 2 to 3 inches of the existing concrete. After the concrete has set you "drypack" the gap with a fairly dry mix of course sand/cement. If you concrete the trench full the new stuff shrinks away and leaves a gap.

Another way i've seen is to dig out a larger section and support the existing founds on small screwjacks which are left in when the concrete is poured.

I have a friend who earns a good living making up "disposable" screwkacks.


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## Tom R (Jun 1, 2004)

jmic said:


> Tom,
> I can't believe your bldg. dept is closed for the week, wow! Do you live in a small town that share's inspector with other town's?
> Joe


You got it, - - small town blues, - - actually found out when I got there the last day open was last Thursday (Dec 15th), - - and they won't re-open 'til Jan. 2.

And yes, inpections are shared with other town's, - - the electrical and plumbing inspectors (from out of town) are available for inspections, - - but the building inspector (hometown) must be out havin' fun somewhere without me. :cheesygri

Kinda' my own fault, - - I went through the same type of (paperwork) problems last year, - - but forgot.

Mrs. tommer says it's my fault, - - who the hell else plans a job every Christmas week?? :innocent:

In defense of my small town though, - - it's really a great town overall!!


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## Tom R (Jun 1, 2004)

Nick H said:


> The way we usually do it over here is to dig out alternate 6' sections then dig out underneath the existing founds and concrete to within 2 to 3 inches of the existing concrete. After the concrete has set you "drypack" the gap with a fairly dry mix of course sand/cement. If you concrete the trench full the new stuff shrinks away and leaves a gap.
> 
> Another way i've seen is to dig out a larger section and support the existing founds on small screwjacks which are left in when the concrete is poured.
> 
> I have a friend who earns a good living making up "disposable" screwkacks.



Great stuff, Nick, - - I really appreciate it.

Interesting theory about the shrinkage/gap scenario. I hadn't taken that into consideration at all. Makes perfect sense.

The screwjack theory sounds kinda like what I had in mind, - - 'cept I was thinkin' 6 footings with 'cut-off' lally columns or somethin'. I wasn't really thinking screwjacks because nothing really needs to be raised or lowered. That's why I say I hate to mess with somethin' that's been straight and level for 40 some years. But I do see where screwjacks would be much more convenient to work with as far as 'exacting' them in place.

Maybe your 'bud' can send me some and I'll send him a 'disposable' check!! :cheesygri 

Seriously though, I really appreciate the input, - - between you and jmic it gives me some confidence to head in the right direction here.


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## jmic (Dec 10, 2005)

Tom,
At least it seems like you're consistent. I know what you mean about living in a small town. Question! How do you do the Quote feature on the top of these posts? 
Joe


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## Tom R (Jun 1, 2004)

I'm probably the last person you should ask anything about computers to, - - but I'll give it a shot if I'm understanding what you are asking here.

For any post that you want to 'quote', - - just hit the 'quote' button in the very bottom right hand corner of that very post, - - and it will start out as your reply. Then you can also 'backspace' and all that to eliminate some of it and just quote the part you want.

Hope I explained it right. Give it a try.


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## jmic (Dec 10, 2005)

Tom R said:


> Hope I explained it right. Give it a try.





Thanks Tom! :thumbsup:


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## Nick H (Nov 13, 2005)

Tom, although underpinning is seen as a "trade" over here and although it can be hard labour involving a lot of hand digging its not particularly difficult. Most builders with experience of excavating and concrete pouring would undertake it. You can get air powered hand shovels, i suppose like miners use, to help dig under the existing founds but it can still be s**tty work.


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## Tom R (Jun 1, 2004)

Nick H said:


> Tom, although underpinning is seen as a "trade" over here and although it can be hard labour involving a lot of hand digging its not particularly difficult. Most builders with experience of excavating and concrete pouring would undertake it. You can get air powered hand shovels, i suppose like miners use, to help dig under the existing founds but it can still be s**tty work.


Yeah, thanks, Nick, - - I'm not worried about the work, - - I just wanted to check around and find the best way, - - which you guys have provided. I figure just one day's labor for me and my helper to trench along the outside and 'set' the 6 supports (think I'm gonna use 'sono-tubed' piers, - - if I get any shrinkage or movement after I'll jack it up and steel-shim it), - - then another day's labor after a week or so to 'under-mine', form, and pour the rest. The whole porch is only 7' X 18', - - piece-a-cake!!


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## jmic (Dec 10, 2005)

I love when a plan comes together. :thumbs:
Joe


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## jmic (Dec 10, 2005)

:thumbsup: Got it.


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## PipeGuy (Oct 8, 2004)

Tom R said:


> ...I just wanted to check around and find the best way, - - which you guys have provided.


 Just curious - why wouldn't you ask the inspector what he's used to seeing and then go with the path of least resistance?


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## Tom R (Jun 1, 2004)

Hmm, - - did you read posts #12, #14 and #16??

That was my original intent, - - just ask "how ya want it?, - - that's how I'll do it".

Although the office is closed I did get (lucky?) and catch one of them yesterday, - - I asked him how he wanted it, - - he asked what I had in mind, - - I told him, - - and he said that's fine, just go for it. Actually, I was hopin' to get a little more input from his end, - - but he was on the run.

If you have any other methods, - - I'm more than interested to hear them. I'll probably start trenchin' and piering on Saturday (the wife'll love that). Then maybe undermine and get an inspection and a pour around Wednesday or Friday after it sets up some.


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## Tom R (Jun 1, 2004)

See, normally (as if this was normal), I would just dig out every other say, 6' section and do it in two phases of pouring about a week apart, - - but for a little 7' X 18' porch I hate to pay that 'minimum' truck charge twice.


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## Tom R (Jun 1, 2004)

I was also even thinkin' pier blocks w/cut-off lally's (or similar), - - that way I wouldn't need any concrete at all for phase-one, - - and wouldn't need to wait on any setting time, - - and pier blocks have 'shim' slots.


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## Tom R (Jun 1, 2004)

Well, guys (and gals), - - there's been a slight change of plan, - - trenched it all out today and the whole wall collapsed into the trench, - - about time for a new porch foundation, wouldn't ya say!! Just gonna have to start from scratch, - - luckily I've got a dumpster right in the yard anyway, - - tomorrow I'll have to bust up the walls and get 'em out of the hole. Mrs. Tommer's just shakin' her head, - - mutterin' something about Christmas Eve, - - not sure just what she's talkin' about!! :innocent:


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## jmic (Dec 10, 2005)

What ya say, Mrs. Tommer backed into the front porch? Oh my, have you called the insurance co. yet ? :shifty:
Joe


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## Tom R (Jun 1, 2004)

Sounds believable, - - I'm always tellin' her anyway, - - women don't steer, they 'aim'!! :cheesygri


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## jmic (Dec 10, 2005)

Tom,
Is the floor part of your existing front porch masonry or wood? And I suppose it has a roof over it right? Just trying to picture your situation.
Joe


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## Tom R (Jun 1, 2004)

It's a slab, - - only about 2" thick, sheesh!, - - yeah, there's a hip roof, that's stayin', - - err, at least if it don't collapse, too. Nahh, - - actually the roof is old, but it's built well, - - and I got her all braced up. The slab will be history tomorrow, - - at this point I'll probably go with a crawl space and a wood-frame floor this time, - - I'll just have to draw up an addendum to the plans and ask the inspector to put it on the fast-track.

The trouble with the walls, - - not only was it the sandy soil 'loosely-put', - - but the 'alleged' footing was only like 2" thick, - - more like a level-starting-pad. We suspected it was gonna collapse anyway, - - so we gave it the old 'heave-ho' (like 'Glass' says he did to his last wife :cheesygri ).


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## Guest (Dec 26, 2005)

*look up ab chance co on the web*

have helicals drilled below frost [3 spaced along front of footing]
weld of to 3/8" 3x6' angle bolted on to side of footer. site will educate you and everyone else. i do earthquake retro in sf. not too many people know about helical anchors good luck tool


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## Tom R (Jun 1, 2004)

Thanks, tool, - - I already decided to trash it and start over, - - well, actually it decided to trash itself, - - it was shoddily built and the best bet is just to go 'head and build it from scratch.

But I do appreciate the input, - - and though you're right, - - I'm not familiar with helical anchors at all, - - I'll check 'em out, - - maybe for a next time.


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