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Enlarging Window Framing Advice

p_550spyder | Posted in General Questions on

I’m looking to enlarging a window in my front room/ living room. It’s on a gable end exterior wall, on the first floor of a two storey house. The joists above and the joists on the second floor ceiling both run parallel to this wall. 

Currently the opening is approximately 48″ wide. I’m looking to widen that to 84″ and bring it down to floor level. Walls are 2 x 4. Height of the window would then be approximately 8′. Ceiling is 9′ tall. 

-I’m looking to remove  the plaster walls, remove the studs that are in the wall and in the way. 
-Add king studs, 2 per side, if not 3 and then add 2 jack studs per side.
-Header would be 10″ to 12″ in height, doubled and looking to use LVLs for extra strength, which would sit directly under the sill plate
-And lastly cut out the exterior walls and add the window (the exterior will be done by a friend who is a bricklayer stone mason)

My questions are :

Does everything I’ve outlined here sound correct or am I missing anything of big importance? 
Second, I’m wondering if I need to build a temporary wall to hold the weight of the house while the existing window faming is removed. It’s a gable end wall so not sure how much it’s carrying weight. Building a temporary wall parallel to it, doesn’t seem to make much sense and would just hold the weight of the joist that would sit directly above it that’s running parallel. What’s the best approach here and do I have to worry about that weight sitting on the exterior wall? If need be, can i place one or two metal jacks under the sill plate temporarily as I build the wall and remove once I’m about to place the header in with jack studs? 

Appreciate any guidance on this. Thank you.

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  1. Expert Member
    Michael Maines | | #1

    Header size is determined by load and span, not by what will fit. There are a few tables here that should include your situation, or you can interpolate: Those tables also show the number of jack studs required. The tables were developed using standard engineering practice. I've done the math longhand many times and it always matches the tables. Be sure to read the footnotes, which include important information.

    This table shows the number of king studs required:

    I just re-read your question and see that you're talking about a gable end. In most cases, gable ends don't have loads on them but in some cases they do. When there is no load, there is no requirement for header size. Do you know how your house is framed?

  2. p_550spyder | | #2

    Hi Michael, Thanks for the reply. Not 100% certain exactly how it's framed, outside of knowing that the joists run parallel, not sure of what else might be a critical factor that might determine if it's bearing some of the load. I haven't opened up the walls yet to see which visual might help to determine. What can I look for to help in determining such?

    Also, as far the header size, if I have the room to fit it and can choose to place a 12" double header in, even if it's not actually needed based off of the span and requirements, logically I just figure over sizing anything structurally can't hurt and just offers a stronger weight capacity. Unless somehow I'm wrong in making such assumption?

  3. Expert Member


    As Michael said, if nothing bears on the walls, adding a header isn't necessary and doesn't buy you anything. The forces above openings in non-load bearing walls are primarily lateral, so using several top plates is beneficial. No need for all the king and jack studs either. All this presumes that enlarging the opening in the exterior masonry, and supporting the new larger lintel, can be done entirely independently.

    One thing to look out for is that the requirement for the new window to be safely glass may kick in depending on how close to the floor the sill is.

  4. p_550spyder | | #4

    Thanks Malcolm. Understood on the header and no need to overdue it with the King or Jack studs as I indicated in my initial note. So no need for any support wall as I open this one, which will make the process a bit easier.

    As for the glass, I do believe once it extends below 18" of wall, and in this case, I"m looking at a floor to ceiling window, the glass needs to be tempered so it can withstand any accidental kick/hitting the glass. So I will make sure to have that window tempered.

    1. Expert Member
      MALCOLM TAYLOR | | #5


      I bet the new window will make a huge improvement to the space!

      1. p_550spyder | | #6

        Indeed! Lot more light and a great improvement overall, with much added curb appeal!

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