The Mullions are just not that bad.

In our last installement, we looked at some rather unfortunate mullions framed in a stairwell.  Let's take a close look at the framing around the wall.  The upper portion of the wall is gable framed above trusses that bear at the top plate.  This is good because it allows the trusses to brace the top plate for out-of-plane wind resistance.  To lessen the axial load on the wall, a three-ply beam spanning the width of the stairwell was placed approximately 3-4ft inside the exterior wall.  Somehow, someone missed a few inches of framing, which resulted in the trusses NOT bearing on the exterior wall.  If the trusses do not bear on the wall, how can they brace the wall to resist out-of-plane wind pressure? 

Mulligan for Mullions

It has been a while since I looked at this picture, but I remember this condition quite well.  As some context, this condition occurs at the fourth floor level of a stairwell.  This wall condition spans from the roof framing down to the intermediate landing between the third and fourth floor.  If we look a bit closer, as in the photo below, we can see that only two studs run the full wall height at each side of the window.  This project was located in a region with a wind speed of 100mph.  As is, this condition required remediation to the mullions and the header-mullion connections to satisfy design requirements.  Had the mullions between the windows been constructed full height, instead of spanning between the headers, the load path would be easier to follow and require less remediation.  

 

Unbearable!

I do feel bad about not getting a second post for January.  I had a slight delay due to the birth of my first child.  My little girl weighed in at 6lb 11oz and made it into this world 13 days before her due date, which coincidentally was today.  I will try to make up for the lapse in posting with two pictures in one post.  (Yes I know, it is cheating when it shows the same thing.)

As the title hints, the corner of this wall is not actually bearing on the slab.  Since this corner is at a shearwall (hopefully the hold down anchor was installed after this visit), at some point during its life this stud pack will see a compression load.  Will this cause the building to fail?  Most likely not.  It will cause the interior gypsum board to buckle.  That would sure be a mess to clean up.  

A second picture below better indicates the true gap between the sill plate and the slab.  You can also see separation between some studs and the sill plate.  If someone were to tighten the anchor bolts to cinch the sill plate to the slab, more separation could occur, which does not correct the problem.  You could fill the gap with an epoxy grout.  This building uses prefabricated walls which should be fabricated to the correct height.  If you fill the gap, what happens at the top of the wall?