Footing Detail 1

[CivilPipe]

I am interested in your opinions on this footing detail. Notice that there is no joint between the footing and the slab on grade.

Thanks!

 

[Once20036]

What is it that you're looking to discuss?
Personally, I would add continuous bars across the bottom of the footing, in lieu of a hooked dowel in each direction.

 

[KootK]

Slab over wall condition is fine by me so long as the sequence of construction works for your project (slab precedes enclosure).

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[JAE]

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[bigmig]

If that slab ever settles good luck, because you're going to need it. I would recommend extending that wall up to the CMU. Stop your slab at the wall.
Otherwise it acts like a big crow bar and levers your wall, distressing it.

 

[JAE]

bigmig - you're right - I meant to comment on the fact that there is no thermal break between the outside and interior slab - in warmer climates maybe not a big deal but in the northern areas with freezing the issue is quite pronounced.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[spermar]

I agree with the comments above. Depending on where you're located, you might want to include depth to the bottom of footing for frost.

 

[CivilPipe]

Thanks so much for your comments.

We have been using similarly detailed footings for years in Kentucky and Tennessee with satisfactory performance. A contractor recently questioned the need for a joint between the slab and the footing.

To respond to a few of the comments above:

The footing depth is always below the recommended depth by code.

Vertical masonry reinforcement is provided including embedment depth/lap splice of dowels.

Space under the slab is always backfilled with crushed stone.

 

[msquared48]

If you are worried about the slab settling, instead of using the stub steel contractors hate as it destroys their forms, you could always make the footing 14" wide and bear the end of the slab on the 2" lip.

A little more concrete, but a lot less hassle.

Mike McCann, PE, SE (WA)

 

[mike20793]

I use a detail like JAE marked up all over the southeast US and it works well. Of course, we don't have freeze/thaw issues that the rest of the country usually has to deal with. Anywhere else, we float the slab at the wall.

 

[thaidavid40]

Why is a reinforced corner joint needed where the slab connects to the wall section? Nix the full return dowel from the slab top bars, and just let the wall bars project far enough up into the slab to create a pinned connection, resisting lateral shear. If the joint at the face of the wall is visible below the finished grade at any point, simply put in a horizontal v-notch reveal there to give the crack somewhere to hide.
Dave

Thaidavid

 

[JAE]

Technically speaking - to resist lateral shear between floor and foundation wall you'd have to develop the bars to full fy on either side of the joint for shear friction to occur.



Check out Eng-Tips Forum's Policies here:
faq731-376

 

[jayrod12]

If they're providing a key, then technically they don't need full development no?

 

[JAE]

If you trust keyways....I don't after seeing so many crack through the years. But again, many don't crack.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[jayrod12]

That's why I used the word technically, I'd be providing the rebar.

In reality, we'd never do this detail, we'd always have the slab separate from the wall and only dowelled at the doors.

 

[Archie264]

If you are worried about the slab settling, instead of using the stub steel contractors hate as it destroys their forms, you could always make the footing 14" wide and bear the end of the slab on the 2" lip.

A little more concrete, but a lot less hassle

msquared48,

Could you elaborate? It sounds intriguing but I'm afraid I wasn't able to follow it.

[Edit] Wait, it may have just hit me. You're referring to making the stem wall 14" wide, bearing the slab on a 2" portion of it and building the CMU wall on the remaining 12" portion of it? Did I get that right?