Grouting 75% solid CMU walls

[campbelltc]

I received a call regarding a residential foundation where the superstructure was damaged/destroyed in a fire. The superstructure has been removed and is slated to be replaced. I have not seen it yet, but the way the owner has described the foundation wall to me (three core, thick webs and face shell) makes me assume that it is 8", 75% solid CMU. To make matters simple for explanation, local code is saying the wall must be grouted solid, even though the owner says there were no signs of distress (I'll verify that in the field). The owner says contractors have told him it's not possible to grout the wall solid. Does anyone know a way to grout a wall like this solid? Can it be done? Thanks.

 

[DaveAtkins]

Can you trump the local code by proving it works structurally? Typically, active earth pressure is used in the design of a residential basement wall. The dead load of the structure above (times 0.6) can be used to reduce the flexural tension in the basement wall. And the latest edition of ACI 530 increased the allowable flexural tensile stress for mortar.

DaveAtkins

 

[msquared48]

Does it have to be solid grouted because it is a fire wall, or is retaining earth for most of the height? For either of these reasons, working structurally will not fly.

Mike McCann, PE, SE (WA)

 

[KootK]

I've always though that CMU foundation walls were to be grouted solid below grade for durability reasons. Water migrating through etc. Perhaps an exception could be made if other measures are taken or the owner is willing to accept more risk.

Why is it not possible for the contractor to solid grout the walls? In extreme cased, you can break the face shells and grout the wall from the side. Nobody's going to be too thrilled about that though.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[CELinOttawa]

If you get into allowing this or backing it up, you'd better be prepared for a later lawsuit from a subsequent owner. Grout filled cells perform so much better than hollow, particularly underground.

Also: Be careful about listening to the contractor's "can't do it" talk... Many contractors are generalists who would never have seen, let alone know anything about, clean outs and face shell openings.

 

[campbelltc]

@Dave - I thought of that and hopefully the code official is amenable if we can prove it works. Thanks for the heads up on the increase in allowable stress.

@Msquared48 - it's not a fire wall but it does retain earth for most of the height - why would it not be allowed if works structurally? Am I missing something?

@KootK - grouting solid usually increases the area by 50% and the section modulus by about 40%. Good structural benefits.

@CELinOttawa - I'm not sure I see why there would be a lawsuit over the masonry (if there are no issues and it is within allowable stresses)?

Thanks, all, for the comments.

 

[CELinOttawa]

I mean to say that if there is a code mandated "grout solid" and you provide the justification to not grout all cells, you're now responsible for all code concerns including and not limited to durability.

Thus in future if the wall fails in durability you may find yourself defending your decisions, even if the cause has nothing to do with your work. I don't know the stats, but I'm willing to bet omissions are a major source of lawsuits.

 

[msquared48]

campbelltc:

I was always taught to grout CMU solid below the finished grade level, and I thought there was a code section requiring this.

Mike McCann, PE, SE (WA)

 

[msquared48]

Masonry Below & At Grade Helpful Member!(5)

thread507-181850

Mike McCann, PE, SE (WA)

 

[msquared48]

Grouting CMU foundation walls below grade Helpful Member!

thread507-98290

Mike McCann, PE, SE (WA)