Concrete Wall Reinforcement

[Andrew Wilkinson]

Hi all

First time poster. Been using previous posts for info for forever!

Question is this: if ACI 318 (7.6.5) and CSA A23.3-2014 both limit reinforcement spacing to 3x the wall width maximum, why do Logix and FoxBlocks tables permit spacing well beyond this? How do they do it? FoxBlocks even has technical bulletin: 1.05.06 which reinforces this. I'm in Canada so we have to abide by CSA standards and don't have the ACI and IRC competing against each other. But from what I can tell, the IRC allows spacing beyond this as well (even though it is supposed to parallel ACI-318). And in reading the commentary for 318-11 it actually says (in regards to 7.6.5.) that using spacing larger than the minimum may be desirable.

*I originally posted this under codes/guides discussion but it doesn't appear very active over there so here I am. Sorry if rules were broken.

 

[KootK]

Welcome to active participation.

How do they do it?

1) They are brave.

2) Their walls tend to be covered by insulation.

3) They've done some testing.

4) The insulating properties of the system tend to reduce shrinkage cracking.

5) They exploit the ever present code clauses that say "do whatever the hell you want so long as it's rational and you're a licensed engineer."

 

[jayrod12]

In many areas, mine for sure, there are residential wall reinforcing layouts that violate those rules but are actually part of our local amendments to the NBCC. I believe offhand that it allows 10m verts @36". Scary.

 

[Andrew Wilkinson]

Thanks for all the input everyone!
I received an update from the Logix Head Engineer in Canada regarding this question:
- Unfortunately, the National Building Code limits ICF walls, unfairly, to 5.5” minimum. That means any ICF wall less than 5.5” by code it has to be designed to part 4 of the code, which in turn says to design to CSA A23.3.
-In previous versions of CSA A23.3, we were permitted to deviate from the design code if we can demonstrate the rationale behind it.
- However, because the concrete in ICFs are perpetually insulated, thus in a good curing environment, we increased the spacing (any cracks that do occur in the ICF will not be visible or structural). This is common practice and is allowed in the residential codes in the US (up to 48” spacing), and is noted in the Logix Design manual.

 

[hokie66]

What a load of rubbish! Cracks that you can't see, but they say are not structural.

 

[dik]

KootK: "Their walls tend to be covered by insulation." and you can't see the cracks...


Dik