openings in CMU wall ... a lot
openings in CMU wall ... a lot
(OP)
I have an interior non-load bearing CMU wall with just enough reiforcings to satisfy the minimum code requirement.
MEP trades came in and put a bunch of openings through it without checking with us first. Some of them are clustered together with only about 3 to 4 inches of masonry wall left in between.
How does one evaluate such situation to say if it is acceptable or not? based on what guidelines/codes/etc.?
What is the appropriate remedy method?
Thanks in advance.
MEP trades came in and put a bunch of openings through it without checking with us first. Some of them are clustered together with only about 3 to 4 inches of masonry wall left in between.
How does one evaluate such situation to say if it is acceptable or not? based on what guidelines/codes/etc.?
What is the appropriate remedy method?
Thanks in advance.






RE: openings in CMU wall ... a lot
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: openings in CMU wall ... a lot
Attached is a rough sketches with the blue circles representing penetrations.
Again, to what degree do we say it is acceptable? And if not, what can we do about it?
Thank you.
RE: openings in CMU wall ... a lot
I would be concerned with the lack of a head over some of those. you may want to add an angle (leg up) on both sides into a grout joint to span that. know that the cmu arches, assuming your drawings is to scale. Since it isn't load bearing, i am going to guess it isn't lateral either?? I second kootk that it is judgement and i am always curious what others have to say.
I just had a job where i had vert. bars at 48" o.c. and guess who added crawlspace vents at 48" o.c. and happened to cut nearly every rebar possible!! a little worse than yours but similar, Mine had to be repaired.
RE: openings in CMU wall ... a lot
Some options:
1) maybe you can verify that there's one solid grouted core between the two primary groups. If so, at 5 PSF interior wind, you may well retain enough wall flexural capacity.
2) If you've got bond beams above and below, you could treat it like a ribbon window. That might also be your steel reinforcement strategy if you have to go that way.
3) if you turn the wall horizontally in your mind and think of it as a shitty, weightless slab loaded with 5psf, it doesn't seem so bad. If your comfortable with FEM and have the tools to do it efficiently, that might be an option. I know, this sounds a little ridiculous. I've got a masonry / FEM goddess in my office that could do this in 30 min.
Thanks for the sketch.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: openings in CMU wall ... a lot
RE: openings in CMU wall ... a lot
Failing payment by the responsible party or the owner, this is simply a "make good existing structure" moment, or a complete write off of any responsibility in writing.
Do not guess; Analyse. This is a simple question of strength and tolerances. What is the strength of the wall, and what does your code require? Treat this as new work, period.
As a profession we are quickly becoming a joke because trades and other professionals see us as push over. Be the exception and do the right thing: Stand your ground. Not your fault, but you're happy to help for the fair price of the work.
RE: openings in CMU wall ... a lot
RE: openings in CMU wall ... a lot
Any desired openings after the fact, must be located to avoid the grouted space where the rebar is, irregardless of the calculated "stress" in the non-bearing wall. This would require a location that does not cut any rebar. If the holes are as nice, pretty and neat as the drawing, the must be relocated to allow a continuity of the wall structure.
This is based on the fact that masonry walls are considered as a unit and the essential continuity. If the small openings are neat cores without cutting rebars, the essential continuity can be preserved because of the stiffness of the wall. Grouting in steel sleeves might help with the location of the penetrations and allow some flexibility for the mechanical contractor.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: openings in CMU wall ... a lot
RE: openings in CMU wall ... a lot
Barring it being your fault (be honest with yourself here) my advice stands. If it is your fault, calling your insurer and then openly admitting this is much easier in the long run, and EVERYONE respects the few people who actually stand up these days and say mea culpa. I haven't had to do this myself, but I sincerely hope I will have the integrity and class to do so should circumstances ever demand.
RE: openings in CMU wall ... a lot
I'd like to particularly thank KootK and EngineeringEric, for your practical advices.
Thank you.
RE: openings in CMU wall ... a lot
Just had a friend show me the drawings to a structural job that was done for less than 0.2% of the project value, or about $0.20/ft^2. *sigh* How much of that place was actually checked? Black box anyone?
Back to the subject at hand, and for a little practical advice: Be very careful about the space available for the mech passing through, as well as the supports, particularly if you are in a seismic zone. Many codes (including here in Ontario as of 1 Jan 2014) require specific seismic checks and restraints. Only become responsible for what you're paid for, but what's more: Make sure that if you pass this, be very careful with your language about exactly what you are saying yes to.
RE: openings in CMU wall ... a lot
Also I'm curious to know more about what you the What do you use?
EIT
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