Below Grade CMU Wall Grouting Requirements

[bhengnr]

Referencing thread507-119706

My coworker and I were discussing if all cells need to be grouted fully below grade. The reason for the discussion was specifically an elevator pit composed of CMU walls. He enlightened me that all cells in a CMU retaining wall must be grouted full per code, but there is no code provision in the IBC or TMS that I could find that states that.

The only reference I could find was in the IRC 2018 R403.1 "All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings..."

Is anyone familiar with a reference to the IBC or TMS requiring fully grouted walls? This is for a commercial building. I understand the logic of it, but it would be great to know the code reference.

 

[bIockhead]

I don't know if it is prescriptively required (sorry for not addressing the "meat" of your question), but depending on the membrane protection, it might not be a bad idea to fill the volume so that water can't collect and sit in there. This comes up more for residential where I think it's one of the rare cases where I would be okay with using mortar as grout, as long as mortar isn't being used to fill any reinforced cells.

 

[Roukkia]

why not use concrete pit walls instead of running cmu all the way down? seems like it might be easier to bring the mason in after pit, pit wall, and sog are poured..

 

[SirScole]

After a very quick cursory search I found a reference to this topic in the DoD UFC Structural Engineering. Under "Chapter 2 Modification to IBC" It states

2104.1.1 - Placing Mortar and Units [Addition]
Masonry walls below grade and elevator shaft walls must be grouted solid.

Here is the link to where I found it in UpCodes.

https://up.codes/viewer/department-of-defense/dod-ufc-3-301-01/chapter/2/modifications-to-ibc#2-8

I hope this helps with your decision making process.

If at first you don't succeed, skydiving is not for you.

 

[masonrygeek]

If there is a real need to grout the block solid, then by all means, but you are increasing the cost by doing so. There was a project in Eau Claire WI where they bid a job with fully grouted CMU foundation walls vs partially grouted walls and there was about a 15% savings. If you reinforce the wall properly and waterproof it as mentioned by blockhead, then you shouldn't have any problems.