IRC 2009 Residential Foundation Reinforcing

[UnthoughtKnown]

IRC 2009 Table R404.1.2(1) requires one #4 cont. bar 12" from the top of the found. wall and one #4 bar near mid height of wall. This is for wall heights less than or equal to 8'.

My thought is that hor. bars in a foundation wall give the wall the ability to act as a grade beam to help bridge soft soils, etc. and to better distribute loads from above. This also helps crack control. But I've always thought rebar near the top and bottom of the found. wall is most effective, creating the larger d' distance (assuming that footing reinforcing and wall vertical rebar is not req'd).

Any thoughts on this specific requirement?

 

[MiketheEngineer]

I presume it is for cracking. Since the middle bar is in the center - it shouldn't be carrying much T load - so it helps with shear.

I generally use two at all three locations and 3 or 4 in the footing.

Little extra steel is cheap in a $M house

 

[MtnManBob]

The wall acts as a deep beam when spanning soft spots. Doubt if it even gets past cracking moment. Rebar is for crack control. Mike is right. A little extra rebar is cheap. Owners hate lots of cracks in their walls.

 

[Forensic74]

I would think its to keep the vertical bars from walking during the pour....

 

[MiketheEngineer]

I too use vertical bars to help place the horizontals at about 4' oc. They seem to cut down on vertical or 45 cracking. Also all on openings I put two bars with 45s at the corners. That really helps.

 

[UnthoughtKnown]

All good points, but the question is why a top hor. bar and middle? Wouldn't it be better top and bottom of the found. wall?

 

[DWHA]

My guess is that if the footing is properly reinforced, and the wall is doweled to the footing, you can credit the footing steel? Just a guess.

I would call out for #4 bars 18" OC each way if I was taking responisbility for it. But, I also get complaints from contractor. Oh well.

 

[hokie66]

Not familiar with your IRC, but based on this requirement, I think it is useless. Why bother to build a concrete wall without adequately reinforcing it?