Grouting Under Beam Pocket in Masonry Wall

[murphy89]

Hello,

Does anyone know where the typical design of grouting 3 courses solid under a beam pocket in a masonry wall comes from?
I see it all the time but don't know where the 3 courses comes from, why not 2, or 4?
What failure mode is governing the number of grouted cores beneath a beam embedded in a block wall?

Thanks!

 

[phamENG]

I don't think that's universally typical. I usually call for the cell under the beam to be reinforced and grouted to the foundation or transfer beam.

But I'd say it's probably trying to preclude a bearing failure. Most fractures at beam seats in unreinforced masonry that I've seen were no more than 2 courses deep. Whether or not there's some sort of formal survey and documentation or just somebody's observation being drawn as a typical detail and that detail being copied over and over and over until it became gospel...who knows?

 

[jerseyshore]

I'm a fill 2 courses solid below type of guy, but that's just because I always assume every contractor is going to cheap out by n-1. I want at least one course solid so if I tell them two then I'm [hopefully] going to get at least the one.

 

[hokie66]

When I use block as a bearing wall, I fully grout it, so don't have to answer that question. To me, hollow blocks are permanent formwork.

 

[XR250]

I mean how much load does it take to punch a grout plug thru a block? I suppose it depends if the tapered core is up or down. That being said, I am like JS and do 2 courses. For high loads, I will do the entire column.

 

[bones206]

I think it's a standard practice that has carried on through the years as a typical detail. Seems like it could have to do with the length of anchor bolts. Personally I call for the cells to be grouted full height of wall below the bearing point. Masons I've spoken to don't seem to have an issue with it. They don't have to worry about installing grout stops.

 

[murphy89]

Thank you all for weighing in on this, I appreciate your responses!

 

[phamENG]

On a related note - if you're going to tell them to grout it at all and weight might be a concern (transfer beam below, weak foundation, whatever), either assume it will be grouted solid or be very clear that they cannot do more than you tell them. I had a case where the mason decided to "make the design better" and grout a wall solid and more than double its weight. I was fortunate that the foundation had sufficient reserve capacity, but I could imagine how that might go sideways on a tightly designed pile foundation or a wall sitting on a steel beam.

 

[lexpatrie]

XR250 -

There used to be some kind of requirement for adhesion testing between the block and the grout. I'll see if I can find something on the subject. I know I read it at some point. Probably something from Amrhein.

This looks like it:

The History and Significance of Coring Masonry Walls, Chrysler, Siggard, 12th Canadian Masonry Symposium, Vancouver, British Columbia, June 2, 2013