#1  
Old 04-06-2008, 08:40 AM
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Default Started digging, stopped digging. Water problems.

Greetings all.

I've been lurking here for some time now, and only recently joining the site. I've looked at the various builds, downloaded the available plans and guides, have found local suppliers for needed goods.

I've been doing all of this for a friend with a big backyard that wants to build an oven. Here's the view from the back door of the house:



The idea is to put the oven in the far corner of the lot, just to the left of the yellow machine.

He's decided on the 42" Pompeii. From the guide it recommends an 80"x96" concrete slab. He spent some time staking it out, then started in with the auger. We're in the northeast, most footings are at 48" to get below the frost line. The plan was to sink four 8" Sonotube footings into the ground.



$75 for the day for the machine. Makes very short work of the hole. Looks like about 4" of topsoil, another 5" of sand/clay mixture, then it appears to be all clay.

We got down to 40" pretty quick on the first hole, auger spinning very nicely. We noticed though that the spinout was turning a little muddy, looking a little wetter the further down we went. Pulled the auger up and out, and found this:



After watching it a minute or so it became this:



The water was almost spurting from the side of the hole about 12" down or so, filled up pretty quick. Sides collapsing in. Reminded me of digging in the sand at the beach.

We then drilled in another about 40' away, in a slightly higher area of the yard. Same thing.

So here's the question: Do we need the footings? I remember reading in another thread on this forum that with enough trap rock as a base, allowing for drainage, it's possible to "float" a slab. Excavate the area, at least 6" of trap rock, then pour the slab on that? Quite often done up in Canada for detached garages. Could anybody give any insight into this method?

Or, if we need to have the footings, we'll have to wait until summer to do the digging, when the water table is a little lower.

All help will be most appreciated.
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  #2  
Old 04-06-2008, 08:50 AM
Il Pizzaiolo
 
Join Date: Dec 2006
Location: Mishigame & Iberia
Posts: 1,168
Default Re: Started digging, stopped digging. Water problems.

If it's really "all clay" down below, your water is running on the top of the clay. Clay does not give up water that fast unless it has sand stringers in it. A pure clay is quite "tight". How thick was the clay (how deep could you go?)

Bail out the hole a few times and see how fast it recharges. It could just be local drainage from the sand/gravel interface on top of the clay layer.

If you have slope to the property, you could put in some draingage pipe and let gravity do the work.

do you know any friendly builders in the area...you could find out what types of foundations are put it there.

Jim
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Old 04-06-2008, 09:40 AM
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Default Re: Started digging, stopped digging. Water problems.

Jim, thanks for all the replies.

I know that the soil does dry out over the course of the year, every 4th of July there's a hole dug (near where we dug hole #2) for a bean pot cook to happen, it's dug at least 36" down, no water is seen at that time.

Here's the thread I was referring to for doing a foundation pour without footings:

http://www.fornobravo.com/forum/27356-post7.html (Another foundation question)

I think it will work just fine, but I'm having a hard time convincing the owner (and $$$ provider). Anybody with horrendous results that wants to add in?
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Old 04-06-2008, 11:27 AM
Il Pizzaiolo
 
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Default Re: Started digging, stopped digging. Water problems.

The key thing on that foundation comment by David is the drainage. You want to keep that coarse material drained to avoid the freezing/ frost heave issues.

I doubt that you're going to have damage the oven if the hearth slab is well reinforced. Consider the hearth and oven as a monolithic unit on your separate floating foundation unit.
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  #5  
Old 04-06-2008, 12:22 PM
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Default Re: Started digging, stopped digging. Water problems.

Quote:
Originally Posted by jbaker View Post
From the guide it recommends an 80"x96" concrete slab.
My plans say 77" x 86" foundation for a 42" oven. Am I looking at the wrong spot?
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Old 04-06-2008, 02:09 PM
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Default Re: Started digging, stopped digging. Water problems.

I've been going by the plans I downloaded off this site. Here's a cut and paste of the materials list for the Pompeii:

Material List 42" Oven
80" x 94" Foundation

(46) 80lb bags of Ready-Mix concrete
(8) 10' lengths of 1/2" rebar, (4) cut to 80";(4) cut to 94"
(4) 2"x6"x8' studs for framing, (2) cut to 83";(2) cut to 94"
(48) sq ft of wire mesh
(12) rebar stand-offs
(104) sq ft of 6 mil plastic sheeting
Handful of plastic zip-ties, or ball of tie wire
1/2 cu yd of gravel
(1) box 2 1/2" framing nails


etc.....

From this link to the Forno Bravo storefront:

Instruction Manuals & e-Books :: Forno Bravo Store

Look on page 58

And I just found this while going way back in the forums:

http://www.fornobravo.com/forum/f6/p...lans-2265.html (Pompeii PDF Plans vs. Website plans)

Now I see where your question lies.

Last edited by jbaker; 04-06-2008 at 06:00 PM.
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Old 04-06-2008, 02:23 PM
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Default Re: Started digging, stopped digging. Water problems.

Quote:
Originally Posted by Xabia Jim View Post
I doubt that you're going to have damage the oven if the hearth slab is well reinforced. Consider the hearth and oven as a monolithic unit on your separate floating foundation unit.
So you're saying (and I promise I won't hold you to this) the idea of a 6.5" well reinforced slab of concrete over a foot (or better) of well drained compacted trap rock will provide a stable foundation for the rest of the build?

I guess our biggest concern is whether we're going to have a slab that will go off level in a big way. A slight adjustment off of level is certainly not a major problem.

I've been hitting out to some of other builder forums, seeing what I can find. Too much info sometimes is not a good thing. Makes one's head hurt.
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Old 04-06-2008, 10:50 PM
Il Pizzaiolo
 
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Default Re: Started digging, stopped digging. Water problems.

Quote:
Originally Posted by jbaker View Post

well drained compacted

Too much info sometimes is not a good thing. Makes one's head hurt.
well compacted and well drained.....

Let me mention a worst case scenario....a good friend of ours has a house built on sand along Lake Michigan. Over a few years we noticed his porch was sagging. Slab on the ground, column up to porch, column up to roof.

We could sit on the beach and look back at his house and it had a remarkable tilt to the roof for 1/3 of his porch due to the settling of the concrete slab. (even before the wine ) The slab was cracked and pulling away from the house,

Okay, that long story followed by a contractor who came in and pumped concrete under that slab and raised the whole shebang back into place, nice and level.

Now I don't believe you will ever experience that kind of problem and do believe that the foundation reference by David will work in your case....again, talking to you local contractors never hurts either.

That last comment of yours is so true....but it's also how you get a comfort level to go ahead....

Do let us know what is decided....
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  #9  
Old 04-06-2008, 10:58 PM
Il Pizzaiolo
 
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Default Re: Started digging, stopped digging. Water problems.

Somewhere I've got pictures from when they straightened the Leaning Tower of Pizza ....er, no, that's near Detroit at Dominoes Farm.....yeah, the Leaning Tower of Pisa in Italy...right!

They dug down, put a collar on the tower and stacked lead weights on the upslope side.....actually brought it back from leaning too far over. (there is surely more to that but it was quite an engineering job)

Good old Wikipedia Leaning Tower of Pisa - Wikipedia, the free encyclopedia

On 7 January 1990, after over two decades of work on the subject, the tower was closed to the public. While the tower was closed, the bells were removed to relieve some weight, and cables were cinched around the third level and anchored several hundred meters away. Apartments and houses in the path of the tower were vacated for safety. The final solution to prevent the collapse of the tower was to slightly straighten the tower to a safer angle, by removing 38 m3 of soil from underneath the raised end. Through this, the tower was straightened by 18 inches (45 centimeters), returning to the exact position that it occupied in 1838. After a decade of corrective reconstruction and stabilization efforts, the tower was reopened to the public on December 15, 2001, and has been declared stable for at least another 300 years
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Old 04-07-2008, 05:27 AM
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Default Re: Started digging, stopped digging. Water problems.

Quote:
Originally Posted by Xabia Jim View Post
While the tower was closed, the bells were removed to relieve some weight, and cables were cinched around the third level and anchored several hundred meters away.
Yikes. I'm thinking we should wait until the groundwater subsides, then dig the holes and sonotube it. Quite a bit cheaper than the cost of 300 meters of cable, and less stress on the neighbors.

I think I'm going to recommend we start stockpiling the needed materials, wait until the water drops, maybe do the holes around July 4th (the owner of the land where this is going wanted to have it in by then. Insert another smiley face <here>). He usually has lots of family visit over that week, extra hands mixing the concrete wouldn't be a bad thing.
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