R602.7.5 Supports for Headers

[para-CAD]

BLUF.  

 

My plans came back with the typical additions required by the County.

This one is new to me.  (See attached image)

 

I thought I knew what I was doing because I framed houses for 25 years all over from Houston, TN, GA, WA and even western Canada and was really good at it. I've never done this and it is never been pointed out to do this before on any plans.

 

But, here it is in the code book so now I'm wondering if maybe I'm not understanding this correctly.

 

Typically, as the opening increases in span, I would always add additional support under the header (locally these can be called anything from jack studs, trimmers, cripples, etc.)

On walls that are balloon-framed two stories high, we would add additional king studs and blocking and other methods to increase the rigidity of that wall. I get that.   Reduce or eliminate hinge points.

 

As I read this code, it appears to state that I need to add additional full height studs, king studs, in accordance with the table they present. So that means every garage door opening at 16 feet or larger would require six king studs at each end (plus typically 3 cripples under the header at each end). I have never seen this done anywhere ever.

 

I hope I'm just reading this and understanding it wrong. Let me know please. Thank you in advance.

 

 

(I broke down and purchased Dragon for Mac so all of this writing is dictation (because #SiriSucks). If I failed to proofread and what I write makes no sense, I recommend just sounding out the words and maybe it will make sense. This dictation method is really amazing.)

[Alaskan_Son]

That requirement has been in there for quite some time now and you are not misunderstanding it.  It's really pretty ridiculous for a lot of situations IMO and needs some serious reworking.

 

I don't have a copy of the code commentary but it was explained to me by an inspector years ago that the requirement was there due to wind loads and after doing a little more research, I came to the conclusion that he was absolutely correct.  The idea was that we needed to replace all the studs being eliminated by the header span with half of the studs going to one side, and half to the other.  Some jurisdictions have specifically amended the code so that it only applies to walls over a certain height, and the ICC itself is addressing it to a certain extent with some notable changes in the 2018 IRC.  They have basically eliminated the requirement for regions with wind-speeds under 115 mph.  I'm not sure whether or not they made any changes with regard to wall height though. 

[para-CAD]

Thanks!  

Great explanation.

 

The code department wants the table included (it seems I'm putting a vast amount of the code book all over my plans these days) but I wanted to understand what I was adding before I just did it.  

 

 

[DRAWZILLA]

I haven't seen or had to deal with that, but all of my plans are stamped by a  licensed structural engineer.

[WesternDesign]

Michael is correct.  There is also secondary effect, tearing of the sheeting at the openings and the additional stitching (nailing) around the opening helps reduce this.  this is also why the trimmers also need to be full length (sill to header).

They primary reason for the code requirement is to replace the studs needed to resist the inward deflection.

It is important to note that this is for the minimum required studs and not just what you have used.  example: if the code minimum for structure was 2x4 studs at 24" o.c. but you have 2x6 at 16" o.c. then the requirement would change since you have already increased the structure's inward deflection strength.

 

Back to racking...

You can see the racking (and how the shtg rips away due to the fewer nails) in this video

 

[Richard_Morrison]

While this requirement may be in there to prevent racking, a Simpson Strong-wall or Hardy Panel is a much better alternative, IMO. 

[Joe_Carrick]

4 hours ago, Richard_Morrison said:

While this requirement may be in there to prevent racking, a Simpson Strong-wall or Hardy Panel is a much better alternative, IMO. 

Yes and the Steel Strong Walls are really good.  I include their details as a PDF when using them.

[para-CAD]

 It’s odd that I have to add this to my plans when no one does this around here. I just walked the dog past a home that is being replaced because it burned to the ground and here are pictures of how they’re constructing it. They must be using approved plans. 

[para-CAD]

The 2018 code fixes this. I just bought it in binder format and was happy to discover this.

 

It’s not in effect yet but it’s nice to see they’re fixing things that don’t make too much sense.

[DRAWZILLA]

12 hours ago, Joe_Carrick said:

Yes and the Steel Strong Walls are really good.  I include their details as a PDF when using them.

Yes, been using a lot of Simpson steel shear walls the last few years,. and for the most part their details wok for me also.

[DRAWZILLA]

11 hours ago, para-CAD said:

 It’s odd that I have to add this to my plans when no one does this around here. I just walked the dog past a home that is being replaced because it burned to the ground and here are pictures of how they’re constructing it. They must be using approved plans. 

By the looks of the holdown straps in the pic, it looks like there will be some kind of shear wall there, they just haven't got to it yet.

[para-CAD]

 All of our garages up here have either straps or some form of hold down but we don’t add anything more than what the hold down requirement is which is typically two or three studs total. 

[Gawdzira]

Locally, what the inspectors have been calling for are double trimmers over a certain length header. Just to keep them happy I am putting double trimmers on anything over 36".

[SNestor]

Not arguing with the code...but sometimes I think these code creators just don’t have enough to do so they look hard for things to regulate.  I mean there are millions of homes out there that were framed without this requirement and...last I looked they weren’t falling down. 

[VisualDandD]

NC went to a 90mph wind load and now almost all garage openings are 'portal frame'.     The heads is run continuous, well past where it would normally just bear on the jacks.

This has become pretty much std around here.

 

[Greg_NY61]

In 2015 IRC they have a table for number studs needed.

 

[WesternDesign]

4 hours ago, Greg_NY61 said:

In 2015 IRC they have a table for number studs needed.

 

Good reference

It is important to note that this is for the minimum required by code stud size & spacing, not what you are actually using.  If the code allows you to use 24" o.c. then you use that column for the # of trimmers, even if you are using 16" o.c.

[Bob-Roraback]

Here is the explanation from the 2015 IRC commentary

 

R602.7 NUMBER OF FULL LENGTH STUDS.pdf

[MikeCSD]

Looking ahead to the 2018 IRC, which will soon be in effect here in CT, they have changed up the king stud requirements in comparison to the requirements of the 2015 IRC. https://codes.iccsafe.org/content/IRC2018/chapter-6-wall-construction#IRC2018_Pt03_Ch06_SecR602

[ACADuser]

This is a problem using a prescriptive method. They say this is code minimum but in a prescriptive table, they must cover worst-case (CYA) conditions.

If you have a long enough wall segment that is designed as a "shearwall segment" it will prevent the racking at the garage opening & the additional king posts are not needed.

You are better off asking the Engineer of record to design the portal frame and or shearwalls. The engineer overrides the prescriptive code table requirement.