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Window Wall (#6)

Window Wall (#6)

Window Wall (#6)

(OP)
Yet another window wall to detail out. This particular wall is framed on top of a cripple wall with a step down foundation to match the slope of the grade. See image below:



A couple questions came up as I was drawing this up:

1.) I've shown the PSL columns framed to the double top plate of the cripple wall (through the floor), in the past I've framed them down to the sill plate or only to the wall bottom plate. In this instance I think it makes sense to frame them all the way down to the sill plate at the top of the stemwall foundation. From a construction point of view it is probably easier to frame them to the wall bottom plate (sub-floor). I would be interested to get some differing opinions on this.

2.) Since the cripple wall is rather short I thought it would easier just to use some threaded rod and coupler nuts to connect the HDU holdowns to the SB7/8X24 anchor bolts. The other option would be to use holdowns on the cripple posts which would involve six more HDU holdowns.

Larger image here:

http://design.medeek.com/images/misc2/WINDOW_WALL6...

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Window Wall (#6)

Are studs and spacing adequate for wind load on the face of the wall? This is the first thing that came to my mind.

RE: Window Wall (#6)

(OP)
The wind speeds at this location are not terrible, but I'm still checking the studs and columns for out of plane loads. I may have to upgrade to a 2x8 wall but I'm trying to avoid that if possible.

My biggest question was how to show the PSL columns, I'm still undecided but from the contractor point of view it may be easier to just frame them from the TJI floor.

I'm finding that a lot of my structural details are rarely followed as I've laid them out. The contractor or sub always seems to figure out a different way to do it and then after the fact they want me to sign off on it. Most of the time the deviations are fine but sometimes they seriously compromise the strength of the structure, and then we have a problem.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Window Wall (#6)

(OP)
Column P2 fails in deflection, looks like the only option is to upgrade to a 3-1/2"x7" PSL. A 5-1/4" deep PSL will deflect 2.25" at midspan, you would think by now I'd just naturally go with a 2x8 wall when the stud/columns get around 20' tall, its the deflections that always end up getting me in the end.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Window Wall (#6)

I'm not from the US, but I see similar problems with contractors in timber structures. They always want to change something to fit their way of work, technology and preferences in materials. This way it is logical to work with the contractor directly.

On-topic: I would frame the columns above TJI joists and connect them in some way with the frame/foundation below.

RE: Window Wall (#6)

Two things...

1. Are the 3.5 X5.5 parallams continuous through the pony wall double top plate? If so, it needs to be shown as such. If not, then the straps attaching the base of the parallams to the foundation need to be added vertically across the double top plate too.

2. The longer continuous double studs at the window openings look problematical to me. If there is sheetrock on the inside here, I would limit the lateral deflection to at least L/360.

Mike McCann, PE, SE (WA)


RE: Window Wall (#6)

(OP)
PSL columns are now continuous to sill plate at foundation:



A MSTC40 strap is applied to the inside of the pony wall dbl. top plate to maintain continuity where the columns descend through the pony wall. There is a ridiculous amount of hardware in this wall, but not as bad as some.

The PSL columns are upgraded to 3-1/2"x7" with a 2x8 stud wall @ 16" o/c

It would be educational to fully document the build and see just how close the contractor follows the plan. In the notes I have required that the EOR inspect the framing before it is closed up with drywall and ext. finish work. I really enjoy getting out on site and looking at some of these things get built. Sometimes talking with the contractors and homeowners leads to a better way of putting things together.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

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