CMU wall footing

[JStructsteel]

Im trying to verify reinforcing size in a CMU wall footing. I always thought it was #5 min, max space 48"

Anyone have code section to verify this?

Thanks

 

[DaveAtkins]

Minimum area of steel in a footing is 0.0018 times the area of the footing.

DaveAtkins

 

[masonrygeek]

I don't know of any code that has that simple of a rebar spacing for block foundation walls. The rebar size and spacing will depend on the height of the wall, height of the backfill, type of backfill, thickness of the block wall, etc. Probably the simplest tables that I have seen are in NCMA's Basement Wall Design Manual (

https://ncma.org/wp-content/uploads/2019/02/TR68B-BASEMENT-MANUAL-UPDATED.pdf),

under empirical design. In many cases, the spacing is much farther apart than 48".

 

[KootK]

We're talking about the verticals dowels, right? If so, for me, it's matching the wall verts which, themselves, would be a minimum of #5@48" in most cases.

 

[JStructsteel]

Thanks, this is a stem wall for footing. Not residential. I dont have an issue with #5@48, just wanted to make sure I was not against code. Consider it unreinfored masonry?

 

[DaveAtkins]

I see, you were asking about the vertical dowels, not the reinforcing in the footing.

DaveAtkins

 

[JStructsteel]

Yes, the spacing. Also, do you guys always require solid grout all cells below grade?

 

[phamENG]

I agree with KootK - match the wall spacing and size (unless you need larger bars at the base - rare for me, but has happened).

And yes, I require all cells to be grouted solid below grade - below flashing and weeps if there's a brick veneer, and have the collar joint mortared below that elevation as well.

 

[JStructsteel]

Thnaks. The Wall above is a 2x4 wall, just the stem wall is CMU. I require it to be solid grout, but the contractor says it doesnt have to be per code?

 

[phamENG]

Is he building it based on the prescriptive code, or based on engineered drawings? If prescriptive code, why are you involved? If your engineered drawings, then he doesn't need to worry about what the bare minimum requirements of the building code do or do not say - he needs to worry about what he's being directed to do by the EOR.

Now of course he's going to complain to the owner, tell the owner it isn't required and it costs more, so you'll need to be able to explain to the owner why it needs to be that way unless you want to have a discontented client.

I don't believe the code says it has to be done, but it likely falls within the "standard of care." In other words, if everyone else specs it and enforces it, and you don't, and something happens, and somebody can convince a judge/jury that the lack of grout may have contributed, it's you're fault.

I cite resiliency concerns. Grouting it will make it stronger and make it last longer. I have a project on my board right now - a CMU building ca. 1950s with erosion issues and slab settlement that appears to be resulting from water moving through the foundation wall. This either wouldn't be a problem or would have taken much longer to become an issue had they grouted it below grade.