demo plan responsibilities

Question

demo plan responsibilities

vato (Structural)

(OP)

12 Sep 11 14:41

I discovered a likely collapse mechanism in a 100 year old theater 5 years ago, produced a report, suggested shoring.  Bow string trusses with rotted bottom chord bearing ends.  Install columns through the roof to support the trusses.  Long story short, another firm designed the shoring, the new owner is tearing it down, and the city wants my stamp on the contractors demo plan which I just got last Friday.

I would like to "bless" his demo plan with a letter that also relieves me of all associated responsibility (likely a dream of mine).  Otherwise, they are going to have to pay for another structural evaluation (the roof has been left open for 5 years) along with a complete set of demolition plans, detailing temp shoring, xbracing, etc.

This is a relatively large demo project for myself and the contractor.  I do have a lot of confidence in the contractor, but I'm nervous about even getting involved, considering all of the possible ways a project like this could go bad, especially when there is such an apparent rush to demo.  The walls could fall onto
lower nearby structures.

So what is my question?  Where is the line typically drawn between the contractor and the structural engineer on something like this one?  How much latitude do you give the contractor in a demo, especially when you are suggesting means and methods?  I feel like I need to be on site the whole time.

thanks for any thoughts

SkiisAndBikes (Structural) · Answer 1 · 2011-09-13 09:12:01

In my experience, if you write a letter "blessing" a contractors demo plan than you are professionally responsible for the demolition plan. If you are not absolutely sure the plan is correct and willing to take responsibility for the plan than you should not take on the project.

In my jurisdiction, following a couple of collapses that occured during demolition, the code was changed to require A)demolition plans and specifications prepared by a licenced professional engineer and B) a minimum of periodic site inspections during the demolition process. In each aforementioned collapses people in adjacent buildings were killed.

There are engineers who specialize in this type of work. They are familiar with the Codes governing demolition, the types of equipment typically used (the demo contractor will want to use the largest sized equipment possible on suspended slabs, given that any other non-construction live loads are not present), temporary protective measures and the procedures/sequences implemented. This is only a partial list of what should be specified. As an aside, I am amazed at how little the demolition contractors in my area pay for these enginering services given the high potential for liability.

vato (Structural) · Answer 2 · 2011-09-13 10:00:52

Thanks Skiis,
Your right on it. There is a lot of pressure coming from the city and the contractor and the owner and I just got involved. So I'm telling everyone we need to take a step back and give me time to understand the current situation, actually do some engineering, and make sure we covered all our bases. I never felt too good about writing a letter "approving" and then saying I'm not responsible. Just trying too hard to be helpful. I'm hoping I can at least keep some height of wall up around this historic theatre perimeter. The tragedy is that it's just the roof trusses, but no one wants to pay to fix them, and they sure don't want to pay an extra cent to tear it down. I'm meeting with the contractor and owner this afternoon to either walk away or come up with a scope of work and a fee that I'm comfortable with.

SkiisAndBikes (Structural) · Answer 3 · 2011-09-13 10:10:31

vato,

I've been in your position before. It's tough telling Contractor's and Owners something that they don't want to hear but after the dust settles I always feel better that the job has been done properly. If they don't like taking the time to do it properly, they are free to go elsewhere. If something does go wrong, regardless whether they rushed you or put pressure on you to accept something that wasn't on the up and up, they will not hesitate to point fingers in your direction. Good luck.

vato (Structural) · Answer 4 · 2011-09-14 12:39:30

So, after a site visit, I find the entire roof and ceiling diaphragm removed, 6-48' trusses in place, along with the City's desire for me to tell them that the 30' high masonry walls won't fall outward during demolition. In addition, the new vertical supports for the timber trusses are creating a force reversal. One truss was removed. One of the rotten bearing end that had discovered. It was a 4ply 3X14, reduced from dryrot to about a 2" square chunk of wood. The contractors were amazed. I was right on the money 5 years ago. This thing was destined for a fall. Now it's just asking for some wind, at we have that here. I have written a letter to City explaining that the time required to produce a professionally designed stabilization/demolition plan along with any increase in the potential safety may put the public at more risk as opposed to allowing this contractor to take full responsibility and continue. I didn't bless any plan, just tried to encourage the city to allow the demo to continue.
Pretty freaky. Now I'm ready for that theatre to meet the earth again.

dik (Structural) · Answer 5 · 2011-09-14 12:50:24

With your involvement, I don't think that you can let the contractor take responsibility.

Dik

SkiisAndBikes (Structural) · Answer 6 · 2011-09-14 13:04:43

Vato,

I don't think you can just rely on the contractor to finish the job. You have been onsite and have knowledge of a potentially dangerous situation and will be judged (liability wise) on you response. If there is something that needs to be done NOW to mitigate the situation, it should be in your letter, perhaps proceeded with a phone call. If the walls are 30' tall and can fall in either direction, you better believe I would be insisting on barriers/hoarding/evacuation within any potential fall zone FIRST. Then someone has to step back and come up with an engineered plan for the workers to safely enter the demolition zone and safely continue with the demolition. If a sidewalk or a roadway or an adjacent building or a park has to be temoporarily shut, so be it.

MiketheEngineer (Structural) · Answer 7 · 2011-09-14 13:05:24

Your name is all over it. Tell them to "HURRY"

vato (Structural) · Answer 8 · 2011-09-14 13:31:55

Your correct skiis and dik. I am revising that letter. Thank you very much. Your attention to my potential f up is much appreciated. I hope I can help you out as much one day.

dik (Structural) · Answer 9 · 2011-09-14 14:11:45

If not you, somebody else on this site already has...

thanks, though...

Dik

vato (Structural) · Answer 10 · 2011-09-14 14:15:00

And yes to Mike, time of the essence. Am I obliged to inform the City or can I let the contractor know of the danger that is now present, (which I have done)? Feels like I need to let the City know what's up asap, but I'm not a cop. They let the contractor proceed and now they want a plan. I was called in by the contractor at the last minute of course, and here we are. Everyone is really concerned with safety, although it would seem otherwise reading this. Four years ago they were cussin' me because I said it would come down, now I can't get it down fast enough. I should have stayed home yesterday.

MiketheEngineer (Structural) · Answer 11 · 2011-09-14 14:47:13

True story.

I was visiting a large renovation in a large city in the Midwest.  The demo was on-going.  I noticed that a concrete column about 12'' x 12'' had become totally un-braced and was now about 50' tall and possibly carrying a very sizable load.  Sure looked that way to me.

So I wrote a short note to the EOR(a very large firm) explaining what I saw and suggested that they take a look at it.  BTW - I wasn't even licensed in that state and said so.  But my engineering instincts just told me that maybe someone had "missed" this problem.

Well, that letter ended up on the Mayor's Desk!!! Apparently - he through a fit!! The EOR asked me to retract it.  I said "NO - just check the damn thing".  Couldn't have taken more than 15 minutes.

They fixed it.

But some days - it seems better to stay in bed - but we have our jobs to do - and the first is to protect the health and safety of the public!!

Hang in there.... do what is right...

SkiisAndBikes (Structural) · Answer 12 · 2011-09-14 14:57:26

Vato,

In my opinion, you are obliged to inform the City if A) there is an immediate danger to the general public or B) if the Contractor is not moving fast enough or decides to dismiss you. That being said, I have brought the City in on a couple of situations via informal telephone call and not only were they appreciative but they were also helpful. As long as they understand the situation and see that everyone (engineer and contractor) are moving forward quickly, safely and competently, I believe they likley will only monitor the situation closely and let you do your job. Good luck, you may be working late tonight!

vato (Structural) · Answer 13 · 2011-09-14 16:21:44

What on earth is fast enough. I've informed the contractor in an effort to mutually reach some solution. Now he's pissed that I didn't come up with a demo plan earlier, although I was never hired to do so.
We agreed that he would outline his plan and I would revise. I got the plan on Friday and made it clear that nothing was getting stamped on Tuesday in order to keep going. I reminded him that he proceeded without a plan and has weakened the structure significantly, and we now have people within a potential collapse zone. "What do we do now?" he asks. So far I have only caused more problems in the eyes of the contractor. Very similar to the last time I looked at this building and warned of potential collapse. Thanks again for all the advice.

vato (Structural) · Answer 14 · 2011-09-15 13:50:29

The contractor is claiming that everything is already lateral braced (as he adds bracing). He is taking my letters to the City today. I have tried my best to explain the situation to him, that first let's make it safe, then we proceed. I also reminded him that the first, and likely one of the most important, task in solving a problem is to identify it, then you can solve it. The building was relatively stable before the removal of the diaphragms, which I discovered on Tuesday. I still think those guys could get through this and it would be safer to just do it, while of course, evacuating the adjacent buildings, which no one wants to do of course. Right now the site isn't even secured. It's a bummer. There was a lot of work that would have resulted from this job, but at least I'm not risking anyone's neck, including my own now. A local architect said everything is ok! He should stamp it. I hope someone's laughing.

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