As i was visiting the job pictures on this site i ran across one posted that made me cringe. Those pictures of the rather large fireplace being built clearly depicted the violation of every code i know of that dictates the approved method to tie facing material to the C.M.U. backup. The pictures as big as life of the corregated metal ties hanging out of the block is a huge code violation. Corregated metal wall ties are for veneer over wood studs only period. If you are not driving nails through them into WOOD STUDS leave them in the gang box. The codes violated were ACI 530-99 /ASE 5-99/ TMS 402-99. On a job site close by a code official caught work in progress that did the same thing and required the building to be torn down and rebuilt correctly! Where was the architect on this job (it was large enough to warrant supervision) On the drawings (under MANDATORY specifications checklist in the ACI CODE 530 notes to architect/ engineer) Specify the location, spacing,& type of accessories not indicated on the project drawings. It is quite clear there were more then one asleep at the wheel.
Where were you with your pompous opinions during the that last 20+ years that we wrote the predecessor to the first ACI 530 code and specifications that were the basis for the various model codes? Also were ever around for the subsequent upgrades and revisions?
Not all model codes are accepted verbatim by local jurisdictions because of local conditions, but the legally modified model code is the legal minimum allowed and is tighter (not looser) than the national model code..
I also do not think I noticed you in the committees on the ASTM standards for testing and materials.
It takes a long time, knowledge and experience to be recognized to be a voting member on a major code. It took me 20 years of committee activity to get on ASTM and MSJC/ACI 530 committees. This is a GOOD thing because you learn and see a lot during that period and you gain a lot of experience, also talk to a lot of others with similar interests and background, so you eventually become better qualified than someone with just an unfounded opinion on a subject. Otherwise, you can be looked on as hair-brained, opinionated person that as been hiding and really unexposed to the real world for construction problems, materials, standards and the practical enforcement. I just was informed that there was a testing program that will change/increase the allowable strength for loadbearing masonry structures above the woefully old and conservative allowable strengths for the present materials since few producers do not bother to test for strength (unless legislatively required) since the normal products are 50% to 100% over the current minimums. It will takes years to recognize the new test results.
Some of the groups that are involved in the process are there just to prove activity and gain political points for the rank and file members. There is one group that is very politically inclined for public appearance, but not respected in the industry.
There is your real expert. He knows more about masonry than the rest of us combined.
I will go ahead and answer for you:
The purpose of wall ties is to prevent deflection of the veneer. Inwards and outwards, but the design criteria are primarily for inwards, i.e. air pressure against the walls.
In seismic code an attempt is made to also prevent detachment, but for normal code that is not a primary design criteria.
So how is this relevant?
Because a corrugated wall tie that is properly installed exceeds the design criteria for both positive and negative air pressure.
I wonder if they considered wind loading in the 1800's when cavity walls were first being built. Here's some of the early wall ties. The iron ones are quite dangerous. The terracotta ones are not so common, as you need to cut quarter closers to cover them on the facework.
It appears from the recently posted info.regarding the usage i stand corrected. The allowing or not,varies more then i was aware! As a result it has been shown to me that in WI. they are allowed. As a result of my error, I APOLOGIZE ,to the viewers,and especially to those in WI. (for they were most affected) by this. I regret this mistake. I'am currently eating my humble pie. Not just a real big piece,but the whole pie. There are several lessons to be aware of. All codes are NOT universal, check and double check to see what may apply in the area one is doing work in F.J.N.
It appears from the recently posted info.regarding the usage i stand corrected. The allowing or not,varies more then i was aware! As a result it has been shown to me that in WI. they are allowed. As a result of my error, I APOLOGIZE ,to the viewers,and especially to those in WI. (for they were most affected) by this. I regret this mistake. I'am currently eating my humble pie. Not just a real big piece,but the whole pie. There are several lessons to be aware of. All codes are NOT universal, check and double check to see what may apply in the area one is doing work in F.J.N.
Stuart, in the 1800's and before they designed with more of an empirical bent, as evidenced by the size of those ties. The intention was the same, even if they did not have more than rough estimates of the requirements. That is not to say that they were not experts, a lot of the knowledge of masonry construction that they possessed we seem to have forgotten, intentionally or otherwise.
Well played fjn, you're a true sportsman. Don't play cricket by any chance do you, we need a few more players for the village team as some of the older ones have down to the the great pitch upstairs.
Tscar,
Have got to be honest, if that was the million $ question on Who Want's To Be a Millionaire I would have needed you as my phone a friend.
I would have gone for negative wind pressure as the primary reason for ties and positive as the secondary. Being a simple bricklayer 'mine is not to
reason why'. I only stick them in the wall when I remember them.
However the jobs I've worked with failed ties have usually had the walls bowing outwards. It could be that the corners help prevent the walls going in, and also the inside brick walls return at the frame reveals against the facework.
Other than tie failure, the most common cause of bowed walls is unrelieved expansion of the brick itself. This could cause inward bowing under the right circumstances, like a z-shaped section, but the normal vector is outward.
Just to lighten things up a bit. While area variations are discussed, here is a joke/quiz that never fails to get the new tender here. They are asked, what holds the masonry units together? WARNING THIS IS A JOKE! Let us see if it is used in your area.
The mortar holds the masonry units together and keeps them apart. - That is a very old definition.
The wall ties (whatever type specified) maintain the spacing between the wythes/layers and are used to maintain lateral spacing and continuity.
With a veneer, you actually have two walls. One is the back-up, which is generally or could be loadbearing and the other is the veneer that only carries its own load since it is supported from below. The exception is the surface applied veneer that is adhered to the back-up and no ties are required.
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