Facade Retrofit: Alternative to Wall Tie?

Question

Facade Retrofit: Alternative to Wall Tie?

enigma2 (Structural)

(OP)

13 Jul 10 12:49

We have a project where we have been asked to come up with a solution to re-connect existing veneer to the structural back up of a 1928 structure. From what we can tell, the back up is a double wythe of clay tile and the veneer is a series of 4" thick solid concrete panels. The panels vary in size, the largest is about 20" x 12". A few of these panels are starting to pull away from the backup. It appears the worst one is sticking out about 1" from the rest of the wall. Removal of one of the loose pieces shows there is no grout between the clay tile and the concrete panel.

The mortar joints between the veneer pieces are very slight--1/8" to 3/16", so the use of a wall tie system seems implausible, since most of these retrofit ties are at least 1/4" in diameter. Plus, since the veneer is a harder substrate than the backup, we are concerned these ties will just get stripped and be ineffective by the time they are threaded in and make their way to the clay tile backup.

We are considering the use of an epoxy adhesive anchor with a screen tube countersunk into the concrete panel. We have some apprehensions that this solution may be a bit too rigid and ultimate introduce the potential for cracks in the concrete panel, but we're not sure what other options we have. We don't need to push these pieces back up against the clay tile, we just need to make sure they don't scoot out more and fall off the structure.

Is the epoxy adhesive anchor feasible? Any other ideas?

Ron (Structural) · Answer 1 · 2010-07-13 17:55:14

I have used expanding foam adhesive for similar application of a historical building of about the same era. Works fine, you just have to be careful to control the foam's volumetric expansion so that you don't blow the bricks off the wall.

hokie66 (Structural) · Answer 2 · 2010-07-16 22:58:41

I have used the screened adhesive anchors for brick veneer, and think it should work for stone. I don't like Ron's idea of filling the cavity with foam, but he generally has good reasons for his suggestions.

Ron (Structural) · Answer 3 · 2010-07-17 16:10:45

hokie66...the cavity is not filled. The foam is injected in dollops at about the same spacing as you would normally have wall ties. The locations are offset so as not to impede drainage or air flow.

Ron (Structural) · Answer 4 · 2010-07-17 16:11:45

and ps...hokie...thanks for the compliment. I appreciate it.

Ron

hokie66 (Structural) · Answer 5 · 2010-07-17 18:42:04

Ron...no compliment, just a statement of fact. Thanks for clarifying the foam idea, but it still wouldn't be my choice, contrarian that I am. I would be concerned about the long term adhesion properties of the foam.

Ron (Structural) · Answer 6 · 2010-07-18 07:35:41

hokie66...a valid concern with the adhesives. The last major one we did was about 15 years ago. Seems to be performing nicely. Similar foams are used for concrete tile adhesion for roofing. Those have over 20 years of service record.

The most significant obstacle we've been faced with for "hard anchors" is hiding them.

Nuccio (Geotechnical) · Answer 7 · 2010-09-29 11:15:33

ve used H&B Helix Spiro-Ties before in brick and terra cotta restoration with good sucsess

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Facade Retrofit: Alternative to Wall Tie?