CMU Partition Top Anchors - Constructability

[bookowski]

There are several variants on top anchors for CMU walls to the underside of slabs above (talking about non load bearing walls here). Although I have specified and/or approved these I am not clear on how easy it is to actually build this. The pictures on the product info look neat - but how do you get the last blocks in and grouted with the anchor in place?

A more logical detail uses angles or similar at the sides of the wall, but this isn't always possible - in particular at edge conditions. For example a brick veneer wall with CMU backup in a concrete building, what's the best top anchor to ensure that it actually gets installed/built correctly?

Do they knock out face shells to slide the block in around the anchor?

For example
Top Anchor Type 1
Type 2

 

[hokie66]

You can use an angle one side, with vertically slotted holes. Another way is to build the walls before the slab, and use dowels with dowel caps which allow for movement.

 

[RHTPE]

Hokie, Building the walls first creates other constructability issues: It may inhibit productive formwork & shoring methods, and; Ensuring there is movement space over the top of the CMU wall is only as good as the workers ability to remember to install a low density foam to provide said space.

What I often see in my little corner of the globe is post-installed angles on both sides of the CMU, with no connection to the CMU.

Ralph
Structures Consulting
Northeast USA

 

[bookowski]

Ralph - Agreed that angles on the outside are better, but this only applies to an interior condition. At the exterior you can't do this unless you wanted to post install an anchor into the CMU, but that doesn't seem great so close to the edge.

Hokie - Definitely couldn't build the walls first in this area, the concrete goes up fast and the walls come ages later.

These anchors are pretty typical - I wonder if they're just not getting installed properly or am I missing something?

 

[jike]

Most partition walls are built after the slabs are poured.

I have typically used one of three methods: 1) angle tight to wall on both sides 2) angle tight to wall on one side with bolts into CMU in vertical slots or 3) Dowels similar to PTA 420.

The bond beams are usually placed at the 2nd course below the slab for partition walls. The course above the bond beam (directly below the slab) should be solid to receive anchors. At each vertical dowel, the blocks are either end blocks with an open end or two half wythe blocks. Grout or mortar can be put in from the end.

 

[bookowski]

jike - If you are doing dowels how do you keep a slip connection? The PTA has a slip sleeve. Although that wasn't really my question. I agree that usually the next course down is shown as the bond beam. So for the top course you are saying they knock off the end face, slide in, and pack from the side? Seems possible but tricky. Lets say you had the use the PTA 422 (first link) - same thing, slide in with a knocked out face and then pack from the end?

 

[Ingenuity]

I have used these Linkhead restraint ties.

Fastened to overhead concrete just prior to mason getting to required height, and placed to approx match courses/perpends.

 

[darthsoilsguy2]

for the sheathed dowels, on the last cut course, masons knockout the web and slide it in and slush solid reinforced cells with mortar or site-mix stiff grout.

curious if anyone has had fire-rating issues because of the angle connections.... many 2-hour walls are called out U-905 in the code summary section and the angle isn't on that UL material list.

i will say that running a beam next to the wall close enough to weld clips to has made lots of fireproofing headaches to spray the wall-side of the beam. the masons on the other hand love that detail, because the beam height drops the anchor point down the wall to an area easier to grout solid.

 

[jike]

I use the dowels for the fire rated connection OR for architectural appearance.

The dowels have a "slip sleeve" as you stated.

For the PTA 422, I would try to space them at 16" or 32" to align with vertical joints at the ends of each block.