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[Nathan Riddle]

I have answered all of those questions. And I realize y'all are giving much time, but so am I, it is rather rude to not read what I write then call me out when in fact I have. If it was an honest mistake, then no worries.

Don't defend a bad idea.

The OP appears to me to be seeking validation for what he thinks rather than seeking a practical, safe solution.

Not correct, I have done what ya'll asked (send them to a 'certified company').

I have also stated I am not doing any work on the project.

At this point I am simply throwing ideas out there. I'm not even advising on it.

Lets revisit "practical" at the end.

When asked for the length of the truss structure, no reply has been forthcoming.

You haven't said how much truss - is this one 10' stick?  50'?  What are they intending to put on it - lekos/pars?  Video projectors?  Movers?  Where did you come up with your 100lb max weight number?  Will this be over people's heads?

One last question - why truss instead of schedule 40 pipe which is a more accepted way to hang lights (assuming lights)?

9ft (3m) 3x sticks one on each wall of the /---\ stage walls.

One mover on each truss stick.

ASSuming, over head height, yes. (though people aren't going to stand directly under this doesn't change the safety though).

Probably because it isn't 'pretty' they're going for a new stage design.

Light duty 12"box truss weighs about 6 lbs/ft.  If the stage is 20" wide, thats's 120 lbs minimum.

36lbs + 1x sharpy (35lbs) + cables <= 100lbs [limit]

With a cinder block building you really need to support the truss from underneath or hang from certified points above, not lag it into a wall.
It would be so easy to lag vertical supports onto the walls TO HOLD POSITION and let the weight be properly supported from below.

TJ Cornish asked why not use standard pipe...and received no reply.

See my above quote of myself and TJ.

It really does appear to be a search for validation rather than an actual discussion.

&

The OP appears to me to be seeking validation for what he thinks rather than seeking a practical, safe solution.

I really have a hard time accepting these two statements/assertions when I am simply giving some push back to crazy ideas like dropping the truss to the foundation through the stage floor or the idea that a cinder block wall can't support the weight.

-snip-  To maintain an acceptable load safety margin may well require reinforcing or re-engineering the wall itself.

I would look long and hard at providing support under the truss from the floor up and anchored to the wall to eliminate the whole issue of shear and cinder block anchoring capacity.

Don't use the floor as a base of support.  You'd need to go down to foundation level, pour or install a proper pad, then use proper sized beams up to or through the floor continuing as high as needed to properly bear the load.

Now, I agree without seeing the structure you're trying to 'cover all bases' including a raised stage (one or more stories above the foundation) and other situations; so I'm giving some benefit-of-the-doubt. I just don't see the practicality of these suggestions.

-Re-engineer the wall
-Foundation to load support

But they have done truss upside down U shapes and 'totem' sticks for mounting the lights and directing the force to the stage floor. I'm assuming they don't want that 'look' they want a 'floating' truss 'look' instead. Thus the truss mounted to the wall.

---

From my point of view I am siting my sources that say that wedge anchors into the mortar joints is the most correct way to load a block wall and entertaining a suitable conversation taking heed to the thoughts of others and not doing any work myself. Others are using experience as a guide, which I appreciate; but I'd love to see some engineering specs stating concrete block walls aren't suitable for holding up Scoreboards or TV's or LED wall's or signs or AC ducting, or whatever else they hold up when you walk around a city or commercial building.

Heck I have an structural engineer looking at a wood glue laminated beam; I asked about the weight it could support. He could care less only cared about the mounting method used.

Getting a structural engineer is all about liability not about actually doing the work necessary to prove that an object is capable of holding the weight.

I think a number of good questions have been raised that Nathan and the church should explore. 

I'm not sure what else you expect responders on a forum to do.  "That's probably OK" isn't something I'll say when talking about hanging heavy things over people's heads, especially when I foresee issues - a benefit of my increasing age and experience, and possibly correlated to my receding hairline.

And I believe have stated clearly that I have directed the church to explore those options.

To the second part, I agree. Too much liability to say 'yea that's safe.' Thats why initially I was confirming my suspicions it was NOT safe. After, I redirected to thinking about 'safe' (relatively) ways to do it - mental masturbation if you would.

I'm sure I just missed it- but why aren't they suspending them, they way they were intended to distribute the load?  They could use motors to allow for easier changing of fixtures, presuming the roof is rated for such a load.

I don't think you missed it. I alluded to reasons why and why not but nothing specific I believe.

Probably cost being the #1, will it be safer? Probably. But I don't think the church is thinking about flying being a viable option because of #2 being where they want to put them. I did initially suggest safety to the structure above in addition to the wall. (Best of both worlds).

[Nathan Riddle]

Sorry I have not had time to comment till now.  Any masonry type structure is very weak in tension.  Also it will fail under dynamic load.  Combine those and your asking for a failure.  I love tap-cons where they are providing a pin to keep stuff from moving.  For example to keep a wood frame wall from moving on a cement slab.  For my air compressor I use wedge anchors to the floor AND straps to the wood frame wall next to it.

Something like truss in a wall is asking for trouble.  The truss will expand and contract more than the wall.  That will cause enough movement long term to turn the wall to powder.  Using a grout line to keep things strait is even worse.  It is a different material forming a stress line.  The grout line will fail sooner than the block.  Look at any crack in a cinder block wall and it almost always follows a grout line.

Now this is really interesting.

Why then do the wedge anchors state that the grout line is where to place them? (I know why, spalling if you go where the block is instead of the joint; rhetorical)

Tom your comments are interesting and true, I have seen cinder block basement walls fail on grout lines.  However I have to ask, we are talking about a 100 lbs or so on a structural concrete wall.  HVAC contractors hang the ductless units on the side of buildings over public sidewalks in the city without an engineering consult and these pass inspection.  Not trying to advocate irresponsibility just trying to reconcile common practices. 

I think my only point since ascertaining the answer to my VERY first question has been this bold statement.

I'm not trying to be irresponsible. Just trying to figure out why it's 'okay' for [those] guys to do something but not in this situation.

[g'bye, Dick Rees]

So I agree with y'all from a liability standpoint of not doing it.

What about when they're going to do it with or without me?

Cheeseburger's into the concrete with lags will be very strong. Then safety into the building steel above. They're not putting more than 100lbs on the truss.

If there's steel up there, why not consider using pipe as TJ suggested and using the steel?  Why the eternal side-track fixation with wall-mounting?

[Nathan Riddle]

Cheeseburger's into the concrete with lags will be very strong. Then safety into the building steel above. They're not putting more than 100lbs on the truss.

And that was my initial response.

"you're doing what now?" "okay sure, just make sure you safety it somehow to the building steel"

...

Bla bla bla, and here we are...

If there's steel up there, why not consider using pipe as TJ suggested and using the steel?  Why the eternal side-track fixation with wall-mounting?

-Because that would require a structural engineer to prove it is capable of holding the 100lbs (or say they load it to 500lbs the 500lb load.

-Its also more expensive and time consuming to get proper rigging/flyable hardware.

-The labor involved to calculate the fly-points so the truss can be 'against' the wall will increase costs stiffly.

-You'll still end up anchoring the truss to the wall so it 'stays' in place.

-Wires coming down from the ceiling are 'ugly' & hard to paint black.

I think intuitively it makes more sense just to use the wall as the support. Though I believe this thread points to the contrary of that intuition.

The sch40 steel pipe isn't pretty and doesn't have the right 'look' there's a reason for trussing, it looks 'cool' and is perfectly suited for flying all lighting equipment when used within the engineering's specifications.

Also, I forgot to respond about using motors and chain for other tasks. I've mentioned that multiple times. They are too expensive of an investment; so, it wasn't even broached with this project.

---

At the end of the day, I agree; cheapest, easiest, most safe, would be supporting trussing from the floor.

Second most would be flying.

Third, would be all-thread through the wall supporting the truss. Using compression which concrete likes

[Tom Bourke]

Tom your comments are interesting and true, I have seen cinder block basement walls fail on grout lines.  However I have to ask, we are talking about a 100 lbs or so on a structural concrete wall.  HVAC contractors hang the ductless units on the side of buildings over public sidewalks in the city without an engineering consult and these pass inspection.  Not trying to advocate irresponsibility just trying to reconcile common practices.

I am not saying you can't attach to masonry walls, just that the considerations are different.  For the most part the items your describing come with or call out pre-engineered  attachment methods.  The mount I bought for my TV came with fasteners for wood studs and listed specific fasteners for use in block walls. The instructions had specific holes recommended for block walls. They also listed several unacceptable
'don't do this!" mounting methods.  This was for an articulating mount rated for a 24 inch reach and 125 lb tv.  I think in terms of code this falls under "approved methods"  If I wanted to do something not listed in the instructions in an inspected public space I would then have to get an engineer involved.

The most common channel strut has slots on the back for mounting that will allow for some movement.  The manufactures also have extensive information on proper mounting methods and the load ratings of each.  Channel strut allows the loads to be spread out and has LOTS of accessories for different applications.  I even use it around the house.  I have a closet system and a workbench built out of it.

In the case of truss to a wall it really does depend on the situation.  I think if they use channel strut properly fastened to the wall and the appropriate truss to strut brackets then it will be fine.  I leave the definition of proper up to the manufacturer of the strut.  The install will have to take into account the expansion of the truss with temp changes, any building movement, and the anticipated loads.  Oh yeah and any potential corrosion issues from steel to aluminum contact.

[g'bye, Dick Rees]

OK.  I assumed truss was being proposed to span the stage, not bolted flat to the wall and chosen because it "looks cool".
Aesthetic issues don't really rank as the decider for me, I guess. 

[David Allred]

  The mount I bought for my TV came with fasteners for wood studs and listed specific fasteners for use in block walls. The instructions had specific holes recommended for block walls.
  This was for an articulating mount rated for a 24 inch reach and 125 lb tv.  I think in terms of code this falls under "approved methods" 

125 lbs at 24"?  Impressive.  Is that with 4 wall fasteners?  The vertical spread is probably very important for the stability of the supporting wall.  If that is the case, unistrut as an attachment go-between would be a benefit (compared to a 12" vertical), but may not be an attractive look (depending).

[David Allred]

Very first line of the thread.

Church asked about hanging some truss on a cinder block wall on their stage.

[g'bye, Dick Rees]

Very first line of the thread.

?..which says nothing about the orientation.  Butt to the wall?  Parallel to the wall?

No, it is open to interpretation.  My mistake was to assume that box truss was selected for the job because there was clear space to be spanned (the primary function of trussing), not because it "looked better".

But I guess that happens these days where appearance trumps substance...

[Tom Bourke]

125 lbs at 24"?  Impressive.  Is that with 4 wall fasteners?  The vertical spread is probably very important for the stability of the supporting wall.  If that is the case, unistrut as an attachment go-between would be a benefit (compared to a 12" vertical), but may not be an attractive look (depending).

OOps, only 22"  But yes, 4 bolts.  This thing is heavy on its own.  My TV is only 70lb or so but I wanted the swing out for attaching cables.  The instructions are pretty funny too.
https://www.echogear.com/tv-mounts/full-motion-tv-wall-mount-for-42-80-tvs-eglf2/

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