header clearance under sliding door?

[LonnieP]

I've got an issue with a client (architect) who is trying to lay the blame of a sticking residential sliding glass wall on me alone.

Beam spans 50'-0" and has a floor mounted (top guided) sliding glass wall system under it. The beam has deflected enough that the 1/2" the glass installer allowed has been used up and the glass is sticking in the tracks around midspan. The glass installer set his upper track before all the dead load was in place and has since (last two years) used up all the adjustment space he had. The installer was the one who decided 1/2" was enough space and he didn't check it with anyone else.

I figured the glass installer would allow about 4" for adjustment, like they do with top hung folding partitions. Looks like i was wrong. Question, is there an industry standard for upper track clearance for bottom supported sliding glass walls or is this something that should be discussed between the installer, G.C. and the SE. In retrospect, I'll put a note on the drawings that will start that discussion on future projects.

 

[Teguci]

Sounds like the Architect's fault (just playing the DC game).

 

[LonnieP]

a2mfk,

OK, here it is! 50'-0" long facia beam supporting 30'-0" long gang nail roof trusses. Beam is a 7" x 30" PSL 2.0E (Yeah I know, it shoulda been steel) that deflects (dead load) a smidge over 2" including creep. The rolling glass door starts about 5'-0" behind one beam end and runs diagonally (about 15 degrees angle away from the beam) out under the gang nail trusses and finishes about 15"-0" behind the other end of the beam (about midspan of the trusses). The truss dead load deflection is listed at 0.3 inches and live load is 0,23 inches. I can't seem to find any info on truss creep.

Not sure how much dead load was present when they set the track, (roofing, maybe, maybe not) but definately no gyp. bd. ceiling or plaster facia/soffit.

The overall door length is 50'-0" +/- and 'center' parting with three panels going left and six panels going right. The door panels are supported on rollers at the bottom and guided in an aluminium track at the top. The only load going to the top track would be out-of-plane wind/seismic. The doors are 12'-0" tall and electrically operated (an after bid upgrade I think) though I think that is a moot point.

Roof live load deflection for the PSL should be 0.8 inches (L/722). A re-roof adds another 0.2 inches (L/3000).

Not sure how the glass installer decided that 1/2" clearance for adjustment was enough, unless he made an assumption based on the afore mentioned typical non-bearing wall detail. I think clearance should have been 1"(partial DL) + 0.1"(partial truss DL) + unknown truss creep (0.1"?) + 0.2"(re-roof) + 0.5"(chicken factor) = 1.9". Not quite the 1/4" the Nanawall people want but I'm not sure this is a Nanawall product.

In case you're wondering, my spreadsheets allow 50% DL deflection for added dry use wood creep and 100% for wet use creep. The above calculated deflections include dry use (Desert area) creep.

If we had used steel we could have ignored creep (except for the trusses) but that wouldn't have closed the gap between 1.9 and 0.5 inches. WE should have caught the door head issue and supplied an adequate detail. THEY shouldn't have assumed that 1/2" would cover all sins, especially when all the dead load wasn't there. I guess that's why they call it "Errors and OMISSIONS" insurance. In this case, it will be below my deductable.

Hopes this helps visualize the condition and helps you recognize similar conditions in the future. A note on the plans about talking with the design team about questionable clearances would have worked wonders.

LonnieP

 

[LonnieP]

Teguci, Yeah, who wants to bite the hand that feeds us?

 

[a2mfk]

Ahhhhhhh, now that is a good post Lonnie! We didn't even know your beam was wood until just now!

I think everything else has been said. Anyone of us could be in this bind, no pun intended. Also a bunch of SEs are going to get your back on this, but that may not help you in the end as lay people generally decide these arguments. But do not admit to any fault and talk to your E and O carrier NOW, as they may have specific legal advice that is very helpful. Someone will end up paying for this and you want your share to be as small as possible if anything, as do they. But like you said, maybe your deductible is less than your share.

Certainly the architect or even as important the supplier and installer of the specialty product should have made you aware of any special deflection criteria for their product. Everything deflects, and this must be allowed for in the product installation and/or in the construction sequencing if it is that critical. I'd present your calcs as clearly and concisely as possible (like you just did) and clearly show this exceeds code requirements. Nobody told you to unnecessary exceed these code requirements or standard of practice as that would have been uneconomical.

From what you have told us, I see no negligence or lack of standard of care here. Poor coordination with the other parties concerned, perhaps if I had to Monday morning QB you at all it'd be you could have asked more questions or put CYA notes on your plan. But that is a "do it better next time" comment, not negligence.

I would think for something that critical they'd get the whole thing built, shelled out with all of the dead load, then have the structure as-built by the manufacturer. And their track is not more adjustable than that, and there is no way to re-tool the track and trim out the track? Guess not or you would not have asked us.

 

[msquared48]

Must be one honkin' wood beam at 50 foot span.

A couple of thoughts here:

If it is deep enough, could you post-tension it to cut some of the deflection?

If not, is there any way to permanently relieve some of the load that the beam is seeing?

Mike McCann
MMC Engineering

 

[MiketheEngineer]

Wood?? Now we know...

Can you jack the beam up and then add some steel plates like .5 inch to one or both sides and lag them in.

Haven't done the calcs - but something along this line should work.

 

[boo1]

I only provided the Nanawall info for one reference of installation requirements.

If you met the design requirements, you did the job you were contracted to do. You were not contracted to design, detail these special equipment requirements. Arch, GC and glazer should have been aware of installation requirements (its there job).

There are many options for repair/fixes:
Resess lower track into slab, pocked upper beam to resess upper track, change tracks, stregthen beam, change door height… but who should be responsible?


Arch appears to be playing the blame game.

 

[ron9876]

I would say that if the design meets the code requirements then the only exposure is that the magnitude of the creep portion of the deflection could lead to a question whether wood was the correct material for the application.

 

[Teguci]

Sounds like the structure is working as designed. Can't say the same thing about the sliding glass wall system. What was the rough opening size shown on the architect's drawings? Did the Architect specify the bottom of the truss/top of door? And finally, I agree, Architect's hands aren't tasty anyhow.

 

[Scoopmeister]

0.25" maximum deflection over 50 feet is Span/2400. Gee why would anyone find that unreasonably conservative?

Your live load deflection of L/722 is way more conservative than code, so you have that. Unless something in the project specs could somehow point to a more restrictive deflection limit, how are you supposed to know?

So who would be wrong, the engineer who does not ask the question, or the architect who does not flag a special requirement? I would say when in doubt, always ask the question in writing, and if the answer is time sensitive (as it always is) state that you will assume code minimums unless informed otherwise in a timely way.

 

[rowingengineer]

Who says we were in doubt? Who says this is a special requirement? who says we should take this into account? I think the structure is more important than a set of sliding doors, shouldn't the sliding door manufacturer take our structure into account, not the other way around?

How could you do anything so vicious? It was easy my dear, don't forget I spent two years as a building contractor. - Priscilla Presley & Ricardo Montalban

 

[Ron]

Let's get back to a2mfk's comments....don't admit responsibility.
Did you review the shop drawings during the submittal process?

This is an architectural feature that has been affected by a presumably proper structural design effort. The architect is the coordinator of the design effort. It is his responsibility to check constructability and set the parameters for design, outside of code issues. He screwed up, unless the shop drawings were sent to you for review and they showed the tolerances required for installation.

If this is a proprietary storefront system (Nanawall, Vistawall, YKK, etc) there is probably a code evaluation report for it. Check that to see if there is a deflection limitation, an installation requirement for waiting until loads are applied before installation or both.

 

[LonnieP]

Shop drawings?, in a house? Not in my neck of the woods. Wood framed houses, even expensive ones, are usually built by the framer with the lowest bid. That usually means non-english speaking workers more focused on the 2:30 tail gate party than the task at hand. The overall supervision wasn't much better on this project.

Unfortunately we had a typical detail on the plan that showed a Simpson STC clip on top of the non-bearing walls (with 1/2" gap). The intent was to avoid incidental bottom chord bearing on the non-bearing walls. If you think about the sequence of construction you'll find a detail like this offers more chance of problems than any benefit.

A word to the wise.

LonnieP