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Uncle Bob
September 20th, 2010, 00:34
Here are some pictures of residential foundations in Oklahoma. Does anyone see this type footing and foundations?

They pour the footing first; and come back and pour the foundation walls;

(right click on picture to enlarge)

http://i27.photobucket.com/albums/c192/RJBuilder/th_022-2.jpg (http://i27.photobucket.com/albums/c192/RJBuilder/022-2.jpg)

and,

http://i27.photobucket.com/albums/c192/RJBuilder/th_023-1.jpg (http://i27.photobucket.com/albums/c192/RJBuilder/023-1.jpg)

Notice that there are no anchor bolts; and, yes this is high winds and tornado alley.

Then they add fill and pour the slab on ground inside.

Uncle Bob

Mark K
September 20th, 2010, 01:17
Reminds me of a time when a seismic retrofit contractor showed me a secret detail. My reaction was that I wish thet would have kept it a secret.

jar546
September 20th, 2010, 07:24
WOW! Really?

RJJ
September 20th, 2010, 07:36
No! Should not have the footing and wall above frost line. Fail them UB:

Uncle Bob
September 20th, 2010, 08:19
RJJ,

Not my call; I'm retired remember. I was out Sunday, trying to keep from getting rusty; and took a few pictures. I take the pictures so I'm sure I wasn't dreaming. This is all I see here in Oklahoma; and, I've looked in at least ten different cities.

I thought that perhaps some of you have seen this type of foundation.

Uncle Bob

TJacobs
September 20th, 2010, 09:14
Maybe trench foundations, formed part above grade???

Mule
September 20th, 2010, 09:37
No! Should not have the footing and wall above frost line. Fail them UB:

RJJ, I don't quite understand about the wall having to be below the frostline. Can you expalin a little more?

UB, I have seen this type of foundation on commercial but not residential. I wonder about load bearing walls and why there isn't a footing/beam under them.

UB, I thought you went back to work for a city???? You didn't like the way they were running the show? OR was this the more high grass and weeds gig?

Uncle Bob
September 20th, 2010, 09:57
Mule,

80 %, high grass and weed gig; I'm not quite desperate enough to get back to work, to become a code enforcement "helper".

"I wonder about load bearing walls and why there isn't a footing/beam under them."

I have taken pictures before of the interior slab preped for pour; and can't find them; but, they "shovel" out a shallow trench approximately where loadbearing walls might be. You can't go too deep or you will hit a water or sewer line. :roll:

And, what I've see is all stick framing here (no roof truss systems) so, there are loadbearing walls on the slab.

Uncle Bob

RJJ
September 20th, 2010, 14:11
Maybe in your area Mule you don't have heavy frost! By placing the foundation wall at grade the wall is subject to frost separating the the wall from the footing. If the wall in UB photos had been monolithic or place below grade then ok. Moisture will collect on the top of the footing and frost will separate the two. Looks to me to be at best 12" of back fill. Maybe that area does not have frost. The lots look to be flat as a pancake so what about drainage.
What is the frost depth in Oklahoma UB?

Robert Ellenberg
September 21st, 2010, 10:15
I have done them in two separate pours in the past. We poured the footers with the bottom going below frost line and left rebar sticking up to tie the walls and piers when they were formed and poured and they of course had anchor bolts in them when they were later poured. Would you know any reason that would not meet code?

pwood
September 21st, 2010, 11:38
Maybe in your area Mule you don't have heavy frost! By placing the foundation wall at grade the wall is subject to frost separating the the wall from the footing. If the wall in UB photos had been monolithic or place below grade then ok. Moisture will collect on the top of the footing and frost will separate the two. Looks to me to be at best 12" of back fill. Maybe that area does not have frost. The lots look to be flat as a pancake so what about drainage.
What is the frost depth in Oklahoma UB?
rjj,
this may be a dumb question, but how do you get the required wood to earth seperation if your cement stem wall is below grade?

TJacobs
September 21st, 2010, 13:49
Maybe they were going to use Simpson Titen HD or similar???:roll:

texasbo
September 21st, 2010, 17:50
I really don't see any issue as long as the footing is the correct depth below the frost line for whatever part of Oklahoma this is. However, I would be quite concerned about the lack of footings and/or piers, and/or foundation walls on the interior. The flimsy footings you describe to support bearing walls on the interior of the house make me cringe.

As others have said, I see this for commercial construction on a regular basis. RJJ brings up good points about separation between footing and wall, but nonetheless, I've NEVER seen the footing and stem wall poured monolithically.

UB: are these foundations routinely designed, signed, and sealed by a PE?

mtlogcabin
September 21st, 2010, 18:14
I have taken pictures before of the interior slab preped for pour; and can't find them; but, they "shovel" out a shallow trench approximately where loadbearing walls might be.

R403.1.1 Minimum size.
Minimum sizes for concrete and masonry footings shall be as set forth in Table R403.1 and Figure R403.1(1). The footing width, W, shall be based on the load-bearing value of the soil in accordance with Table R401.4.1. Spread footings shall be at least 6 inches (152 mm) thick.

That would only be a couple of full shovels when you already have a 4" slab. Now anchor bolts are suppose to extend into the foundation 7" then you should have a couple of inches of concrete below the bolt. What is the minimum thickness of a footer? I can find width but not thickness except for the spread footing.

Around here it is 12" per local engineer requirement.

peach
September 21st, 2010, 19:02
The two piece way of foundation wall is pretty common... there SHOULD be dowels from the footing into the wall (or at least some kind of keyway) that holds the two together. If they don't install anchor bolts (or straps) into the wall after they place the concrete, the choices are pretty limited. Our friends at Simpson have invented a retrofit product (also good for seismic and lateral loads)... but the are expensive and hard to install.

RJJ
September 22nd, 2010, 07:21
Here is my rational: It might meet the spirit of the code, but it will produce negative effects in colder, moister climates even with dowels.
In milder climates I don't believe it to be an issue. However in wet areas could produce excess water in the stone beneath the concrete slabs. OH YA vapor barrier. I forgot it will hold out all moisture. Well I am not gone to go there for now. Back to my rational. It is base on just pure good construction.
Example: Frost depth 32" and just for kicks let assume an 8" thick footing.
Now the bottom of the footing needs to be at the 32" mark or slightly below. Footing place and now either a Block wall or poured wall are place on top. Dowels will be need any way you look at it. (or key way) The dowels are not meant for uplift, but rather lateral movement. Sure some uplift is afforded by dowels but the end result is at a minimum. Oh yes minimum code!
Now when we place 24" of earth back against the wall to cover from footing top to finish grade we have protected that intersection of wall and footing with 2' of earth. Now true it is not below frost, but it certainly has increased protection from frost, A greater volume of earth to disperse water drainage and an increase uplift factor base on the amount of dirt.

The photos above are just plain cheep construction with no care for real time factor that effect the structure. I would have no problem with a wall and footing in if it were monolithic, but that would take a little know how and planning.

Robert Ellenberg
September 22nd, 2010, 09:10
MTLog--I believe spread footers are the only type addressed in the prescriptive code and therefore the 6" minimum applies to any of them. The code calls for the footer to project beyound the edge of the foundation wall making the footer wider than the foundation wall and therfore "spreading" the load. I believe this is true whether you are considering the continous footer required for the exterior walls or pier footers on the interior. If someone else knows something that I don't please jump in.

RJJ--I was surprised at your comment that dowels only provide minimum uplift resistance as if that were somehow getting by. In south Florida where wind lift is of major concern and footers and walls must be designed by an PE, they rely heavily on the rebar to tie the walls to the footers to conteract uplift. However, just based on watching heavy equipment do demolition jobs where there is straight pieces of rebar imbedded in concrete, I believe they offer a huge amount of uplift resistance even if they are not L or J bars but those are much better.

RJJ
September 22nd, 2010, 17:12
Robert: Let me restate that in this manner. Dowels only placed in the vertical provide a minimal uplift factor. When tied to a horizontal then the factor is greatly increased. I sometimes dwell in simple terms and factors. Dealing with contractors has taught me to speak in basic forms of communication. If I provide to much technical information then they tend to become glass eyed and place the pencil behind the ear. Then removing their cap and scratching the top of their head in total confusion.

Depending on the size of equipment in relation to the type of wall and size and manner of dowels, ties and bar one could assume that. The average back hoe has between 2 and 5 tons of force on the curl of the bucket. Some more! Frozen water or ice can far exceed that.

Robert Ellenberg
September 22nd, 2010, 19:38
RJJ--thanks for the follow up. I am a contractor/designer and believe it or not, didn't get glassy eyed or put a pencil behind my ear! Now having said that, I am not offended as I know what you often encounter. But it is not confined to contractors as UB's comments on some inspectors reflects. The real difference is attitude. I strive to study the codes and do things correctly. I have been working on several designs I hope to start producing as kit houses next year. I monitor this forum regularly in an effort to get everything EXACTLY right. Code requirements are there for a reason.

peach
September 22nd, 2010, 20:37
Hi Robert,

Well, this forum isn't really for "the golden answer"... it's a group of Code geeks each with an opinion on everything.

RJJ: most of these applications have the upright dowels tied to footing steel and short foundation walls.

The IRC spells out what the footing depth to width needs to be to prevent tipping/punching shear. That's the minimum.. but you can't have a wide thin footing; it's a ratio. R403.1.1 (the projection on each side of the footing can't exceed the thickness of the footing.

RJJ
September 23rd, 2010, 09:37
Peach: from the photo can't tell if they have rods and dowels or how they are configured. Also, not saying it does not meet code just that there are better ways to produce a foundation.

Robert: glad you are on board.

ewenme
September 23rd, 2010, 12:27
We see this type of foundation almost exclusively. Frost depth here is 30" and that requires the bottom of the footing to be below or at frost depth. Wall has to extend a minimum of 6" above finishd grade. We require footing/foundation drainage and damp proofing of all foundations, including crawlspaces. We do have quite a few slabs on grade, which are usually poured after the foundation, and a thermal break between foundation and slab is required. We also see shallow frost protected slabs/foundations; a different animal too.

P.S. Anchor bolts must be poured in place; or get an engineer to figure out the alternative!