Segmented glass wall Nanawall.

[Daniel.858]

Subject: Segmented glass wall Nanawall.
I’m tasked with designing a remodel in a wood framed single family home. The owner wants to expand two opening in an exterior wall to 12 ft wide each. Both openings are to have nanawalls installed. After reading posts about engineers having trouble with nanawalls and header deflection, I’m questioning the wisdom of using a wood header at all. The owner is willing to use LVL or Glulam headers, but I’m not sure that is enough.
Has anyone had luck using wood headers with nanawalls? What advice would you give to an engineer designing for nanawalls for the first time?

 

[KootK]

Let the numbers be your guide. If you can make the L/720 & 1/4" requirements in wood, then wood it is. Take care that you've got the total deflection covered including creep etc. Conversely, you may well be able design for only the amount of deflection that can reasonably be expected to take place after the nana wall system is installed.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

Many of the nanawall type systems I design for call for no more than 1/16" deflection - about impossible to design for.
I have called manufacturer's numerous times to let them know how unrealistic this can be. Even the wood shrinkage can be 1/16" Pretty much falls on deaf ears.
The techs who install them tell me they can be adjusted so they do not need such a tight tolerance.

 

[bhiggins]

I recently had a remodel job with an existing Nanawall header being loaded with new loads from a deck. The contractor refused to unload the header and install a new one as I had suggested, so instead added a LVL ply to the existing header. The header was designed for a total additional deflection to be no less than 1/4". The header deflected 1/8" due to dead weight of the new deck and the door wouldn't open and close normally. Thankfully, the door was readjusted and works fine now.

I typically design Nanawalls and sensitive sliding glass doors as 1/4" deflection max.

 

[XR250]

The header deflected 1/8" due to dead weight of the new deck and the door wouldn't open and close normally.

Wow, if it deflected 1/8" from the deck DL, it will deflect about 1/2" from the LL (unless the deck DL is larger than normal)
Sounds like the LVL was not sized properly (among other things)

 

[bhiggins]

The existing 8' header was a double 11-7/8 LVL header, I actually added additional 2 PLYs because it is taking a point load from spiral staircase on the deck, this is way overkill for that span and loads. I say the deck deflected 1/8" but I really mean it deflected a minuscule amount and caused the door to have issues.

 

[Daniel.858]

Thanks for the feedback. I asked the architect if the client had settled on a brad or manufacturer, because I wanted to look up their specs. He said that they had narrowed it down to a few options. Then he through it back at me. He said, “You might actually have an opinion, as the engineer, to make it easier on all of us.” It sounds like he is trying to get away from any responsibility here. What do you all think?

 

[KootK]

I don't think that it's unreasonable of your architect to seek your professional recommendation for stuff that's withing your purview (product sensitivity to structural performance). Heck, it sounds downright collaborative.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

downright collaborative

Astonishing.

Wood is capable of providing the stiffness you require, however it is generally at a cost premium. When items are deflection sensitive I'm typically tempted to provide steel beams. Around here, a 3 ply LVL costs almost the same as a W12x19.