Creep!

[mbryan]

Brick and Concrete in High Rises

Another revelation from the 1970's (Just more fun and interesting stuff.)

In high rise construction with brick veneer over reinforced concrete structure, horrible cracks began to develop in the brickwork. These cracks were horizontal, diagonal and vertical. Portions of veneer would begin to bulge outward. Brick would bulge outward past window frames. It was a pretty scary thing to see brick in this condition 15 floors up.

The concrete block back-up was installed on each concrete floor and went to the bottom of the next floor. The brickwork was continuous from the bottom of the building to the top. Of course, the brick and block were tied together with duro-wall or some other form of anchorage.

The cause turned out to be a concrete phenomenon called "creep". Concrete shrinks as it cures and gives up its moisture. A high rise concrete structure looses some of it's original height during this process. The brick and block are cured materials and will not shrink. Creep was literally crushing and pinching the masonry out of the structure.

What needed to change? They solved the problem by bolting support angles for the brick veneer at each floor. Both the brick and block stopped one bed joint short of the floor or angle above. This joint was filled with a mastic to serve as a compression joint.

[Marcel R. Cyr]

Hi. Michael;

Addenem to this topic would be, that in that same time frame arena, brick veneer and metal stud back-up was also popular.
Exterior drywall sheathing was installed on the metal studs, usually of 20 gauge which is down 2-4 gauges to todays standards and wall ties were screwed in to the metal studs using regular drywall screws. These have rusted over the years and electrolises has also taken its' toll and showing up as the brick veneers letting go from it's back up system.

Walls have been seen to start bowing out and Engineers finally figured out what was happening.

Today, wall ties are screwed through the metal studs using stainless steel screws on top of dense glass sheathing which is covered with #30 felt and a vicor strip is installed under the wall ties before it is achored to the backup wall.
Brick is now limited to 25 feet in height before a relieving angle has to be installed to carry the load for another 25 feet.

The weight of the brick fascade is transfered to the structure in lieu of weight overburden of the brick wall itself.

Don't things change in 30 years!

Marcel

[mbryan]

Indeed they do...

I have a post in the exterior section called "brick veneer metal studs and smashed cars".

But, you'll notice that step one in the failure of Brick over metal stud was the failure of bond between mortar and brick. This was caused by using a highly flexible structure behind an inflexible facade. The failed joints along with changes in pressure and stack affect permitted moisture to be drawn in bahind the brick veneer to rust away the anchorage. See my post in the exterior section called "metal studs + brick veneer = smashed cars"
The learning never stops....

[Marcel R. Cyr]

Hi. mbyran;

Interesting post. Reminds me of what I said in the earlier post.

I remember this occurrence of the early 80's, and remember that it stemmed to the installation of brick veneers without a relieving angle and brick ties that were atached to metal stud back up systems that were not compatible to the electolysis factor. The combination of both were it's demise.

Today, double dip galvanized anchors and stainless steel screws have joined in the Engineered remediation design to prevent that occurrence. Moisture intrusion in the cavity and drainage plane have also been upgrade to help in this design to eliminate brick facade failures.

I believe that even today, the definition of Experience lives on = a whole lot of mistakes. And that includes Engineers.

I was a Mason Foreman for the Company I still work for in 1975, and brick veeners were always an issue then, but fastners were limited to manufacturing technology for those years. Boy I am glad that position only lasted a year and a half. I have been a Project Superintendant ever since and as of yet have not figuered out who makes the biggest mess in Construction, Dyrwallers or Masons!! ha. ha.

Marcel

[mbryan]

Well, certainly, if clean up is a factor, it would have to be masons.

[Marcel R. Cyr]

Michael;

I think it might be a tie.



Marcel

[Kenton H. Shepard, CMI]

"Today, wall ties are screwed through the metal studs using stainless steel screws"
Marcel


If the problem is galvanic corrosion, then the less noble of two metals in contact with each other will corrode. Before, it was the screws. Won't the same problem still exist with stainless screws, except that now since the steel stud is the less noble metal, the steel around the screw will corrode rather than the screw itself? -Kent

[Marcel R. Cyr]

Hi. Kenton;

The concern with fastners on masonry veneers, is mostly the cavity side more than where or how anchors a used to the structure. Fastners are to be protected in the Cavity of a wall system where it is always subject to moisture intrusion.


ANODIC END
(negative "Base-Metals")
Magnesium
Zinc, including zinc galvanize finishes
Aluminum
Cadmium
Aluminum-Magnesium-Silicon alloys
Copper-Aluminum alloys
Iron and Mild Steel
Cromium
Lead
Tin
Nickel
Brasses
Bronzes
Copper

(Positive "Noble Metals")
CATHODIC END
Stainless Steel (Austenitic S. Steel)
Silver

"Galvanic Action" ocurr when two dissimilar metals come together in the presence of moisture where they act as a short-curcuited galvanic cell and corrosion will occur.

Galvanic Action can be reduced between two metals in the presence of water or moisture by a seperation layer of such as a Neoprene or other inert spacer between the metals.

The problem in the past having used the dyrwall screws, was more in the cavity where it is holding the ties, rather that the attachement to the disimilar metal where it is always dyr or should be.

Another instance of material action (ex.) Aluminum hand rails in concrete.
Sodium and potassium hydroxides released by Portland Cement are very harmful to zinc and Aluminum in continuously damp conditions. To reduce corrosion the Galvanize Steel could be epoxy grouted into the concrete,instead of using cement grout. The Aluminum could be painted at the base where it is to br grouted in with an inert application.

Hope this helps.

Marcel

[Marcel R. Cyr]

[quote=mcyr]Hi. Kenton;

The concern with fastners on masonry veneers, is mostly the cavity side more than where or how anchors a used to the structure. Fastners are to be protected in the Cavity of a wall system where it is always subject to moisture intrusion.


ANODIC END
(negative "Base-Metals")
Magnesium
Zinc, including zinc galvanize finishes
Aluminum
Cadmium
Aluminum-Magnesium-Silicon alloys
Copper-Aluminum alloys
Iron and Mild Steel
Cromium
Lead
Tin
Nickel
Brasses
Bronzes
Copper

(Positive "Noble Metals")
CATHODIC END
Stainless Steel (Austenitic S. Steel)
Silver

"Galvanic Action" ocurr when two dissimilar metals come together in the presence of moisture where they act as a short-curcuited galvanic cell and corrosion will occur.

Galvanic Action can be reduced between two metals in the presence of water or moisture by a seperation layer of such as a Neoprene or other inert spacer between the metals.

The problem in the past having used the dyrwall screws, was more in the cavity where it is holding the ties, rather that the attachement to the disimilar metal where it is always dyr or should be.

Another instance of material action (ex.) Aluminum hand rails in concrete.
Sodium and potassium hydroxides released by Portland Cement are very harmful to zinc and Aluminum in continuously damp conditions. To reduce corrosion the Galvanize Steel could be epoxy grouted into the concrete,instead of using cement grout. The Aluminum could be painted at the base where it is to br grouted in with an inert application.

Hope this helps.

Marcel

[Robert J. OConnor]

Mike ... good info for inspectors/PE's who also do commercial inspections ...

[Marcel R. Cyr]

Robert;

Should I take that as a compliment or should I say someone learned something.

I hope it is both.

Marcel