Masonry control Joint .. or not

[rt06]

Typically in CMU load bearing wall we place vertical control joint every 20 ft or so. Has anyone have the experience to reinforce a wall based on TEK 10-3 to increase spacing between joints (say 120 ft)? In a recent projct the Arch is asking so but I am hesitating to blindly follow TEK 10-3. Thanks a lot.

 

[JedClampett]

That TEK should be banned from Architects. I wouldn't trust it. I've seen some walls that had pretty beefy horizontal reinforcing crack where the CJ's were missed. Due to those observations, I've never tried to stretch the 24 to 30 foot limits.

 

[larsacious]

I am with Jed. Don't ask a mason to do something out of the ordinary unless there is 100% inspection.

 

[rt06]

Thanks Jed and Larsacious for the input. I have similar experience ( I am at south). However, I heard that in west coast where seismic loads necessitate large horizontal shear reinf (say bond beam spaced at 16 or 24 inch), the control joint is rarely used. Any folks from California can confirm this? Thanks.

 

[rowingengineer]

depends on the hieght of wall but I have done over 100ft without problems for a 9' hieght walls. have used H blocks (don't know is they are called this all around the world) in this instance.

An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[Bobber1]

From California: I use a lot of horizontal reinforcing; bond beams at 24" at least. I, too, have gone over 100' with these walls with no joints. Fortunately they were on good soils. Our philosophy here is to have many small cracks held tightly together with the horizontals. We also typically solid grout our walls.

Bob

 

[hokie66]

Bobber1,
Understood, but when you solidly grout a wall with lots of horizontal reinforcement, why do you say you have bond beams?

 

[a2mfk]

I have always carefully detailed CJs in terms of wall openings, returns, etc. and at 20-25' o.c. with a high degree of success. I deal mostly with partially reinforced CMU (48" oc max), bond beams only at the top of the wall, in Florida...

I understand not using CJs if you have lots of horizontal reinforcement as others have stated.

Stay in your comfort zone!

 

[structuresguy]

I always specify control joints at 20-25' centers as well. And like the previous poster, I am in Florida, typically don't have bond beams except at floor/roof levels, and partially grouted (16" o.c to 32" o.c. pretty common).

I think you might be successful in long runs of walls without openings, if using intermediate bond beams, without control joints. But as soon as you start adding openings or intersecting walls, or wall height changes, you definitely should be adding control joints.

I have reviewed masonry cracking on several projects, some mine and some designed by others. Usually I find they have the typical control joint layout/spacing covered, but have not paid enough attention to locating joints at critical locations. So these get missed, cracks develop, and then on review it becomes obvious why the wall cracked where it did.

Bottom line, you can't have too many control joints. If you are not comfortable, make them put the joints in. Or make the architect and owner sign a release relieving you of any responsibility for wall cracking, moisture ingress, corrosion damage to wall reinforcing, interior and exterior finish failure, and any other issues that may arise from cracked masonry walls. I think when you put them on the spot, they will allow the joints.

 

[JLNJ]

We routinely allow 50 to 60 foot spacings between control joints. Often you don't want a control joint for structural reasons (i.e. longer shear walls are better, you might not want control joints at continuous CMU lintels, diaphragm chords should be continuous etc) and 20' seems just too conservative. Showing every control joint in every wall is tedious and costly as well, but if you allow the contractor a lot of flexibility in placement, he might place a joint where you don't want it.

I also routinely spec heavyweight sidewire reinforcement for joint reinforcement, even in low seismic areas, to help control shrinkage cracking.

 

[rt06]

Thank you all for the valuable info. It is interesting to know different constructions in different areas.