header clearance under sliding door?
header clearance under sliding door?
(OP)
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.
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.






RE: header clearance under sliding door?
RE: header clearance under sliding door?
What was the originally calculated deflection. I would have used that and added some for "give". Did you know it was going to carry glass sliding walls??
1/360 seems appropriate - but that might not be enough under these circumstances. I use 1/600 for masonry, tile, etc.
Any simple way to "jack up" the beam and stiffen a bit??
RE: header clearance under sliding door?
You should never, but never, "assume" these things. Verify, verify, verify, and in writing.
Mike McCann
MMC Engineering
RE: header clearance under sliding door?
RE: header clearance under sliding door?
Just because the installer isn't smart enough to know the beam will deflect has nothing to do with engineers. The builder should be in charge of this and if experienced (as required by most building regs) should have been able to handle this without issue. Also the architect should have been experienced and included this in his window spec, I would just pass the buck back.
I don't communicate with installers, I see nothing sticky about us designing to reasonable limits and everyone following suit.
ANY FOOL CAN DESIGN A STRUCTURE. IT TAKES AN ENGINEER TO DESIGN A CONNECTION."
RE: header clearance under sliding door?
I am not surprised you did not talk to the glass installer. Unless this is high rise, your job was done long before that trade showed up to site.
I can't imagine the glass installer is a full time commercial guy. Any commercial trade we deal with would know that a 50'-0" piece of iron will deflect more than 1/2".
Did the architect ever ask you how much the beam might deflect? What does his detail show? Were you provided his detail? Who approved the shop drawing for the glazing? It is his job to specify the glass requirements, not yours.
Brad
RE: header clearance under sliding door?
I normally design to a 1/2" total deflection limitation, depending on the span ratio, for headers over windows and doors. That lends to some larger beams than normal, but keeps me out of situations like this.
Communication, if you know the supplier, helps. But, I agree, that proio communication with the installer is not the norm. However, as you suggest, a note to the installer as to what limitations you set in your design would be helpful.
Mike McCann
MMC Engineering
RE: header clearance under sliding door?
RE: header clearance under sliding door?
ANY FOOL CAN DESIGN A STRUCTURE. IT TAKES AN ENGINEER TO DESIGN A CONNECTION."
RE: header clearance under sliding door?
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"The structural integrity of the header is critical for proper operation. Vertical deflection of the header under full live and dead loads should be the lesser of L/720th of the span and 1/4". Structural support for lateral loads (both wind load and in the stacking area when the panels are stacked open) must also be provided.
THE ROUGH OPENING SHOULD BE LEVEL, PLUMB AND SQUARE AT ALL POINTS. THERE SHOULD BE NO UNEVENNESS OR BOWING. MAKE SURE THAT THE HEADER IS NOT TILTED OR TWISTED. THERE SHOULD BE NO BUMPS ON THE SURFACE WHERE THE SILL WILL SIT. THE SIDES SHOULD BE IN THE SAME VERTICAL PLANE AND NOT OFFSET OF EACH OTHER. A TRANSIT AND OTHER SIMILAR PRECISE MEASURING EQUIPMENT SHOULD BE USED
For better performance .... all dead loads such as upper levels, roof, etc. be constructed before a unit is installed."
RE: header clearance under sliding door?
This is great, did the architect inform the engineer of this? is this for all systems of similar build? what is full deal and live loads? Should an engineer have to change his design to suit this specific door, or should the door work to the engineers design?
In my opinion this is a cop out statement by the door manufacturers. If they want a door to run 50' on a header than they need to have more adjustment in there system.
ANY FOOL CAN DESIGN A STRUCTURE. IT TAKES AN ENGINEER TO DESIGN A CONNECTION."
RE: header clearance under sliding door?
I have had this discussion when extra interior loads suddenly (magically?) appeared and the footing/pad settlement was excessive.
RE: header clearance under sliding door?
As for the beam in question it easily met all applicable deflection criteria including L/360 for plaster. Just not the 1/2" for the remaining 1/3 of the dead load that was added after the upper track was set.
The Nanawall requirement of 1/4" or L/720 gives the installer ammunition for his argument. Seems the best course for the next project is a note on the drawings to have the installer talk to the design team before setting the upper track. Communication is usually good to have and would have stopped this problem before it got started.
RE: header clearance under sliding door?
RE: header clearance under sliding door?
RE: header clearance under sliding door?
I don't know many carpenters/steel workers/even engineers who could measure that...
Maybe with a good laser .....
RE: header clearance under sliding door?
Does the beam element meet these requirements? (What is the measured defection?)
Don't the architect, GC, steel supplier, steel erector and glazing installer all share in the liability??
Since glazer installed the glass wall out of sequence (before all loads were applied), I would think that the glazer and GCs have primary responsibility.
RE: header clearance under sliding door?
There was no special contract requirement other than the building code. We didn't even get the architectural details untill just before backcheck. The beam easily met all code defelction criteria. I think GC and installer should share in remedial costs. Not so sure about the Arch. and other trades. The out-of-sequence issue is the most troublesome. We'll see what happens.
RE: header clearance under sliding door?
How does anyone know how much the beam deflected?
If its one door, the amount of overall beam deflection is not very important, its the amount of change in the sliding glass door opening, which should be insignificant on a standard door.
I need more info but this does not sound like your problem unless the beam has a major deflection issue.
I look at residential doors and windows all of the time and people try to blame structural movements on their poor operation. Rarely is it the structure...
RE: header clearance under sliding door?
RE: header clearance under sliding door?
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
RE: header clearance under sliding door?
RE: header clearance under sliding door?
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.
RE: header clearance under sliding door?
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
RE: header clearance under sliding door?
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.
RE: header clearance under sliding door?
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.
RE: header clearance under sliding door?
RE: header clearance under sliding door?
RE: header clearance under sliding door?
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.
RE: header clearance under sliding door?
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
RE: header clearance under sliding door?
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.
RE: header clearance under sliding door?
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