Mat thru Masonry Joint

[marinaman]

I've got a job where I have a concrete foundation wall that is about 6' tall, and atop this wall, metal stud framing extends to the roof. The wall is veneered in brick. The brick veneer has alot of architectural character to it, in that it bumps out, away from the building, low....and is the typical distance from the building, high.

Since the brick is built-out, away from the building, at the base.....to support the multi-wythe veneer above, a 12" CMU block wall was laid outside the face of concrete wall, to support the 12" of veneer thickness above (12" because of precast sills used). The 12" CMU wall is below grade and is about 6' tall.

All this being said, the GC placed a drainage mat on the face of the concrete wall, laid the drainage mat horizontal atop the footing, and then laid the 12" CMU wall on top of the drainage mat. So the first mortar bed is actually a drainage mat.

By the way...the veneer is to be 22' tall.

The waterproofing was not detailed like this on the construction documents. The waterproofing, below grade,was on the outside of the 12" CMU

Now, the GC wants to know if it was ok to lay the 12" block on top of the drainage mat. The 12" CMU is to be reinforced and grout filled. Right now, its just hollow CMU with dowels (he's not grouted anything yet).

What do you guys think about this situation? I don't like it. I've been looking at ACI 530 and the IBC code, and all I see is mortar...I do not see a provision for something like this.

 

[JAE]

A very weird construction that's for sure.

Now, the GC wants to know if it was ok to lay the 12" block on top of the drainage mat.

You'd have to contact the drainboard manufacturer to see what sort of compression their board can take.
Typically they are designed to be below grade, with lateral soil pressure applied - but that would range from zero to 1300 psf, say, for 20 ft. of soil.

Your 22 ft. of veneer and 6 ft. of fully grouted CMU would weigh about 1,720 plf. Over a 12" width that is 1,720 psf. More than 1300.

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[masonrygeek]

You could engineer this to work out, but prescriptively it's not a good idea. Masonry doesn't like tension or flexing and if the drainage mat compresses differentially, it could crack the wall. As JAE says, check with the manufacturer to see what the strength of the mat would be, but I would be concerned. Typical flashing and weeps above grade are a good design or filling all voids between the CMU and concrete solid below grade to make it a barrier wall is appropriate.