Masonry Control Joints

[CTSeng]

A very popular wall system thru much of Florida is the use of continuous cast in place concrete "tie" beams typically 8"x16" instead of masonry bond beams at the tops of 8" masonry walls. From my experience in other areas of the country I try to encourage the use of full height control joints thru the wall and "tie" beam at typically 20' on center. And as a result I often get the usual "I've never done that" or "that's not done here" response from both architects and contractors.

After some research I beginning to have a change of heart since the "tie" beam is effectively restraining movement similar to the foundation. Does this sound reasonable or should I not be giving in?

 

[UcfSE]

I'm in Florida. We stop joints at tie beams also.

 

[DaveAtkins]

The tie beam at the top of a CMU wall should NOT have a joint through it, because many times it acts as a diaphragm chord.

DaveAtkins

 

[JedClampett]

I'm confused. If you have tie beams, don't you have cast-in-place concrete "tie columns" every 16 ft? What do you need control joints for?

 

[jike]

I agree that most often I have seen the engineer detail the joint so that it stops below the tie beam. As Dave Atkins says: the tie beam is used as the diaphragm chord.

If provisions are made for some other element to act as the diaphragm chord, then go ahead and run the joint thru the tie beam. Either method should work, if designed properly.

 

[JLNJ]

If the joint stops just below the tie beam what good does it do? Doesn't the bond between the beam and the masonry just below it keep the control joint from opening up as designed?

I think we routinely put in too many control joints, and as a structural engineers we want the longest most continuous length of wall we can get!

 

[DaveAtkins]

JLNJ,

You are correct--a continuous bond beam will prevent the top of a control joint from opening properly. But if the bond beam needs to be continuous for structural reasons, then I think that supercedes the need for a "perfect" control joint. And as you get further below the bond beam, the control joint should open properly.

DaveAtkins