Block & Brick

[Darren]

Here's a question for all you Mason contractors and design professionals.

The project I'm on consists of 8 inch block back-up wall with either brick or polished block as the exterior veneer. There is a gap of 4 inches between the block and brick/polished block. 2 inch insulation to be installed over a vapor barrier between. There are 3 questions that are ongoing between me, my project manager and the mason contractor (of which we are waiting the answers of an RFI).

(One more piece of info- the back-up wall passes outside the steel columns).

1) should the control joints be at the columns or between the columns?

2) should the control joints of the back-up wall and the veneer line up?

3) Does the bond beam continue thru the CJ or should it break at it?

whats your thoughts?

[mgbinspect]

Here's a question for all you Mason contractors and design professionals.

The project I'm on consists of 8 inch block back-up wall with either brick or polished block as the exterior veneer. There is a gap of 4 inches between the block and brick/polished block. 2 inch insulation to be installed over a vapor barrier between. There are 3 questions that are ongoing between me, my project manager and the mason contractor (of which we are waiting the answers of an RFI).

(One more piece of info- the back-up wall passes outside the steel columns).

1) should the control joints be at the columns or between the columns?

2) should the control joints of the back-up wall and the veneer line up?

3) Does the bond beam continue thru the CJ or should it break at it?

whats your thoughts?

From past experience, which is now approximately twenty-five to thirty years old:

1.) Control joints always seemed to line up with a door or window jamb. I don't recall them coinciding with columns. In smaller structures, where steel is the sole structure, the masonry is independant and it shouldn't matter. Normally, if the masonry was the structure, there would be no columns in the outer walls.

2.) Yes, they should. Normally control joints had a piece of keyed rubber that served as a weather seal and more or less a backer for the sealant that was later added. Back up and veneer always shared the same control joint. This was consistant in commercial work, schools, prisons, etc.

3.) It seems to me that the bond beams did break with the rest of the wall at the control joint, but since there is steel running through the bond beam, it really shouldn't matter all that much. Keep in mind that a control joint isn't there to manage settlement cracking. It's there to handle expansion and contraction of the materials due to temperature variations and/or shrinkage.

(similarly, expansion joints aren't in concrete flat- work to manage settlement either, but rather to manage inevitable shrinkage cracking as the material cures and shrinks slightly. This same action is what causes concrete high rise structures to loose height as the concrete cures, which is known as "creep".)

[AHI in AR]

...similarly, expansion joints aren't in concrete flat- work to manage settlement either, but rather to manage inevitable shrinkage cracking as the material cures and shrinks slightly. This same action is what causes concrete high rise structures to loose height as the concrete cures, which is known as "creep".)

Actually, you just described a control joint, not an expansion joint. An expansion joint is there to allow the concrete to expand due to temperature rise. Using a softer material in the joint accomplishes this. The job of a control joint is to control where the slab cracks rather than to crack in a seemingly more random fashion. Of course, they don't always do that successfully.

[mgbinspect]

...similarly, expansion joints aren't in concrete flat- work to manage settlement either, but rather to manage inevitable shrinkage cracking as the material cures and shrinks slightly. This same action is what causes concrete high rise structures to loose height as the concrete cures, which is known as "creep".)

Actually, you just described a control joint, not an expansion joint. An expansion joint is there to allow the concrete to expand due to temperature rise. Using a softer material in the joint accomplishes this. The job of a control joint is to control where the slab cracks rather than to crack in a seemingly more random fashion. Of course, they don't always do that successfully.

You are correct, and yet the control joint is there for the same reason - not in anticipation of settlement, but shrinkage. Of course they do come in handy to, as you have state, encourage even settlement cracks to happen in a specific place.