Expert: Ted Barnhill (Principal, Design45 LLC) - 11/25/2007

Question
Hi Ted,

I would like to put french  60'' opening french doors in my basement but I am
not sure how I can be structurally ok.

My basement is separated by a 12'' thick concrete wall. This wall is 80'' tall.
On top of this wall there is two 2x8'' laying flat and then the 2x8 beam for the
house floor are resting on top of that.

Kind of like this :

  |                      |                          |
  |                      |                          |
  |                      |                          |
---------------------------------------------
---------------------------------------------
         Concrete wall


Note that the concrete wall support the floor beams going on side of the
house and another set for the other side (meaning it is not a continuous
beam accross).

I doubt the two 2x8 laying flat will support the load if I do a 60'' opening in
this wall and making a 'regular' triple header will mean that I can't fit a 80''
tall door.

I was thinking using metal beam instead of the two flat 2x8 but will that do
the job and will I be able to find such beam (meaning same hight as the two
2x8 flat) ?

So any help/idea is appreciated.

Thanks.

Answer
Geoff,

Thanks for the diagram.  You have a couple of options, but before proceeding I recommend that you consult an engineer or knowledgable contractor to look at your entire project.  This is because the concrete wall in question may be doing other structural work besides holding up your joists; especially, it may be a shear wall preventing your home from "racking".

When it comes to sizing your header, you could:

1. Install a flush header, in line with your joists.  This would probably be 3 - 2x8s (verify with your lumberyard given your joist spans, # of floors above, etc.).  You would cut your joists flush with the faces of this beam, and install metal face-mount joist hangers to hang the joists.  This would be my preferred method unless you have many pipes or wires obstructing the way.

2. Have an engineer properly size a steel beam for your span.  3" is a standard steel depth for tubes and for "I" beams, but depending on your loads it may not be deep enough.  You would be able to notch the ends of your joists up to 1/4 of their total depth (that is, 1 3/4" or so) to gain extra space for your beam.

Either way, you'll also want to have your engineer verify the jamb reinforcing of your concrete wall (below the new beam ends) and the size of footings beneath.

Good luck and enjoy your french doors.