Header span

Reply

  #1  
Old 02-28-09, 12:45 PM
Member
Thread Starter
Join Date: Dec 2004
Location: South Florida
Posts: 1,166
Header span

I am 2x6 framing in a carport. I'm framing down the existing beam for a header for an 8-foot garage door. The wall I am framing is non-bearing and is between two 6x6 posts. The door openig will be 7-feet high, which leaves me only 8" below the beam for the header. Once I subtract the 3" for the double top plate I am installing, I end up with only 5" for the header. I figure if I add a 2x6 below the header, I have enough room for a 2x4 header, made from a sandwich of 3 2x4s and two 1/2" plywood plies.

I have been unable to find detailed span tables online, but I've been able to extract this info from various sources: for a double 2x4 header, I the max span is 4 feet, and for an 8 foot span I need a double 2x8.

My question is, what is the max span for a TRIPLE 2x4 header with a bottom 2x6? Also, is there another option I haven't considered? A reference to a source for this info would help also.

My understanding is that, because the beam supports the roof, the header doesn't support anything, so the only issue is whether it will sag in the middle.

Thanks in advance!

Steve
 

Last edited by suobs; 02-28-09 at 01:08 PM.
Sponsored Links
  #2  
Old 02-28-09, 01:26 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 20,508
If I can just skip your questions, I'd forget using the double top plate (what's the point?) and use a triple 2x8 header with (two 7/16" spacers) under your beam. (provided you have room for king and trimmer studs on each end).
 
  #3  
Old 02-28-09, 01:35 PM
Member
Thread Starter
Join Date: Dec 2004
Location: South Florida
Posts: 1,166
OK, part of the problem is I'm unclear on how critical the final height of the garage door opening is. Your method puts me 1/2" over. Significant?

Yes, there's room at both ends, in fact a short section of wall, also part of the problem - this would mean ending the double top plate (intended to tie the wall frame to the beam) at the end of the walls and having the header directly under the beam. See any problems with that?
 
  #4  
Old 02-28-09, 02:43 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 20,508
Usually the rough opening for a 7' x 8' door is exactly 7' x 8'. But if the rough opening is a little bigger, you can always pad that down with plywood or what have you, to make it "exactly" the size you need later. This is often not necessary, however, because you usually will add a jamb inside the rough opening, and the jamb will be shimmed so that it is perfectly level and plumb with the garage door. A garage door weatherstrip (like a door stop) is usually added too. I don't think it's bad to have the rough opening be wider than what is called for if you are going to add a jamb and weatherstrip, because what happens is the thickness of the jamb and weatherstrip covers up too much of the door. (IMO).

Again, as far as your double top plate is concerned, if the existing beam (above) is wood, I don't see why you want a double top plate. You can toenail every stud up into the beam. You'll toenail the 2x8 header to the beam too. The king studs on each end of the new 2x8 header will be toenailed to the beam. And you'll have trimmers under each end of the 2x8 header. All the other studs will be like trimmers under your existing beam. No top plates are needed with that beam up there.

Now if the beam is steel, then you would probably want a top plate. Or if you were trying to frame the entire wall on the ground and then stand it up, you might want a top plate. But to me, it's unnecessary and would be just as fast to just frame it up under the existing piece by piece.
 
  #5  
Old 02-28-09, 05:36 PM
Member
Thread Starter
Join Date: Dec 2004
Location: South Florida
Posts: 1,166
Thanks for the detailed response. The top plate is to hold stud plate tie straps, required top and bottom by code on new construction in s. FL. So is 2x6 framing. I'm enclosing an existing pole barn carport, but the framing is considered new construction. Ironically, I'm having to toenail the studs anyway to hold them in place so I can nail the ties to the studs without knocking them off kilter.

Also the beam is double 2x12 wood, so the top plate brings the wall out to 5-1/2" to match the thickness of the studs and the existing posts.

Anyway, I'm thinking I can dispense with the double top plate above the garage door frame - the top plate would end where the short wall sections end at the garage door jambs, i.e. above the last king stud before the trimmers. Then the header would take over. I think you agree?
 
  #6  
Old 02-28-09, 07:19 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 20,508
Well, I know they do things a little differently in Florida, and I will certainly defer to any framers who are in the know with Dade county codes (because I'm not!), but it still makes no sense to me to have a top plate, or a strap that starts at that top plate and goes down onto the new studs below. No matter how many straps you connected to your new top plate (below the 2x12s) it won't tie the lower structure to the existing structure. IMO, you would need a strap (like a Simpson MSTA18) long enough to span from the existing top plate above your 2x12 header down onto the new studs that will be toenailed under the existing header.

And I'd probably add another 2x12 and plywood onto the header so that it's flush with your framing rather than go with the top plate. (or if it's inaccessible for some reason, I'd just pack out the portion that is exposed.) That way the whole exterior of the framing will be flush. But that's just me. I'd love to hear any other opinions... I wish Chandler would pipe up. He must be on a date tonight.
 
  #7  
Old 03-01-09, 06:47 AM
Member
Thread Starter
Join Date: Dec 2004
Location: South Florida
Posts: 1,166
Yes, it's occurred to me that there's not a major tie between the new double top plate to the gable roof, but there is the following: 1) the new double top plates are 16d nailed 8" OC up into the existing double 2x12 beams, and 2) the 5/8" CDX plywood siding will be continuous from the framing up to the top of the exposed part of the double 2x12 beam. The walls are being framed in place over a new 9" concrete poured curb, not lifted into place, so the studs go in after the top plates are nailed in place. The beams are blocked out on the interior with 2x4s to match the wall. The only place continuous straps to the 2x12 beam are used is at window king studs because they will support hurricane panels.

I don't have the options you're suggesting because it was designed this way by an architect/engineer and approved by the county. The architect's explaination is that the new framing is being reinforced for lateral (wind) force and that the straps tying the existing 6x6 posts to the beam and gable roof are adequate for uplift. The walls also are not designed to support anything since it's an existing freestanding carport. I've considered adding the same type of straps upside-down between studs to tie the top plate to the beam more securely.

Each garage door has a short section of newly framed wall on one side and an existing 6x6 post on the other. My questions primarily stemmed from how to deal with a gray area left by the architects when they made the note at the garage doors to "Frame down existing header [meaning the top beam]" without further framing detail for them. Most (including Chandler if I remember right, the county, and the garage door installer) seem to agree that this is reasonable because nothing is being supported there - engineering is not needed. Just frame it down in a standard way, so to me the main concern is making a header that will support itself adequately.

So I'm just trying to take it from there and plan the garage door framing using good advice from you guys at doityourself.com on how to construct and support the headers . . . so I don't freak out the inspector with something crazy.

Steve
 

Last edited by suobs; 03-01-09 at 09:23 AM.
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes