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Questionable Insulated Grade Wall Detail?
5

Questionable Insulated Grade Wall Detail?

Questionable Insulated Grade Wall Detail?

(OP)
Hi all. Our firm is designing the foundations on a new building and we have been asked to use the attached detail for the grade walls. I have a few concerns regarding this detail, such as the settlement of the slab, the metal studs bearing on rigid insulation, and room for the connection of the metal studs to the block below. I suppose the settlement of the slab could be addressed with the proper compaction of the fill but is my concern justified on the other two points? Does anyone have a suggestions on a better approach? It is my understanding that the builder is concerned about meeting the insulating requirements of the local jurisdiction and is the reason he proposed this detail. Thank you in advance for your thoughts and suggestions.

RE: Questionable Insulated Grade Wall Detail?

Is the stud wall load-bearing?

Some issues I see:
1. The connection of the studs to the 6" CMU might be tough to do - concrete screws perhaps? Must resist lateral wind forces.
2. The studs, if load bearing, will only compress the block as it is much stiffer than any insulation - however, the load would be eccentric, applying moment to the 6" wall.

We use a 1/2" joint between slab and grade wall with a thicker wall - and avoid the stud "overhang".

RE: Questionable Insulated Grade Wall Detail?

I would suggest 6" or 8" concrete wall with insulation on the exterior face, aligning with the metal panels. Wall should be doweled to strip footing.

BA

RE: Questionable Insulated Grade Wall Detail?

(OP)
The stud wall is not load bearing. I was going to suggest they use an 8" block and extend the insulation horizontally into the building below that slab rather than bringing it up to the top of the slab and having it exposed inside the building. I think they are concerned about any insulation gap between the foundation insulation and the insulated wall panel. I don't know whether or not that concern is justified.

RE: Questionable Insulated Grade Wall Detail?

If it's non-load bearing, there's no particular problem with it, though it's sort of awkward since the metal stud is balancing on the edge of the CMU. I wouldn't accept it for a load bearing wall.

As an alternate connection, simple might be best - replace the CMU wall with a cast-in-place wall wide enough for the metal stud to sit on. It may be more expensive than a CMU wall (though that's hard to say, depending on the construction schedule and the rest of the building. If there's not already going to be CMU elsewhere on the job, it might be cheaper) but it'll be easier to transfer any loads you might have, and will simplify the light gauge installation.

Brian C Potter, PE
http://simplesupports.wordpress.com

RE: Questionable Insulated Grade Wall Detail?

I'd be concerned about the thermal bridge, where the cold CMU wall conducts directly to metal studs.

RE: Questionable Insulated Grade Wall Detail?

(OP)
One adjustment to the proposed detail is that according to the builder they would fill the block with concrete for the entire length of the wall.

RE: Questionable Insulated Grade Wall Detail?

waytsh-

If they're going to do that, why bother with the CMU at all? Just go ahead and make it a cip wall.

Brian C Potter, PE
http://simplesupports.wordpress.com

RE: Questionable Insulated Grade Wall Detail?

Insulation on the outside with concrete parging or something else over it...

Dik

RE: Questionable Insulated Grade Wall Detail?

I think it is poor practice to have the exterior grade within 2" of the interior slab height. Where I am, it is illegal. I would like to see the cladding extend below the top of the block (or concrete) wall. So I would align the outside of the grouted block wall with the outside of the studs.

RE: Questionable Insulated Grade Wall Detail?

missed that Hokie... and you're correct... in these environs, there has to be a minimum of 6" and the bottom plate has to be PT.

Dik

RE: Questionable Insulated Grade Wall Detail?

(OP)
Thank you all for the valuable input. Hokie, you are correct of course. I forgot to shift my soil down on the sketch. The 2'-10" dimension to the bottom of the soil should read 2'-6".

As for the type of construction I am not sure why the builder would not rather just go with a poured wall unless he is not set up well for that type of pour.

RE: Questionable Insulated Grade Wall Detail?

I liked Dik's suggestion about the insulation on the outside. That will be better for the thermal bridging to the studs. The metal cladding will align with the ext foam and you can just flash down or parge it.

______________
MAP

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