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Do I have to remove the old window jambs when installing new nail flange window?


Eugene Ichinose's Avatar
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04-18-17, 02:14 PM   #1  
Do I have to remove the old window jambs when installing new nail flange window?

I am in the process of replacing an old single hung window with a new nail flange dual pane window. I have removed the old window but I do not know if I need to remove the 1 inch thick wood jamb frame. If I do, the new window will not have any material for the nail flange to nail in to. I am wondering if I need to remove them and expose the bare 2x4 framing studs or if I can just nail them into the existing 1inch thick jambs of the old window.

 
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04-18-17, 02:36 PM   #2  
Installing nail flange window in opening with sloped sill thats not flush

I am installing a nail flange window and am wondering what to do about the old window sill. It is sloped at an angle towards the exterior and on the exterior side of the wall it protrudes 1 inch from the wall (ie it is not flush). As you may know nail flange windows need to be nailed flush against the wall on all sides. Also the rough opening needs to be flat on all sides as well. So do I take the sill out and replace it ? Or is there a way to modify the existing sill so I can install it correctly?

 
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04-18-17, 02:43 PM   #3  
If your window has a nailing flange on all four sides, then, yes, the sill will need to be removed. I would check all the measurements, because nailing flange windows are normally fastened to the OSB and framing, and not normally to the old window frame. Are you removing the old frame? If so, the sill comes out with it.

 
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04-18-17, 02:43 PM   #4  
Take the sill out. Replacing it with framing that lays flat. Check the window dimension.... rough opening should be about 1" bigger than the window.

 
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04-18-17, 02:44 PM   #5  
This ties with this thread. No need to open new threads on the same window. http://www.doityourself.com/forum/do...not-flush.html

I merged the threads.

 
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04-18-17, 03:08 PM   #6  
As far as the jambs go, remove all of your old window... trim, jambs, sill, etc.

Then like I said, make your rough opening 1" bigger than your window is. (so that you can have 1/2" shims and 1/2" of insulation on each side of the new window.) Add framing to your existing rough opening as needed. Consider keeping the rough opening centered with the size of the old opening. (Might need to add 3/4" on each side rather than 1 1/2" on just one side.)

 
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04-18-17, 04:41 PM   #7  
By add framing, you mean by using 2x4's, right?

 
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04-18-17, 04:44 PM   #8  
What is an OSB? I dont want to remove the old frame, but am willing to if it is best to do so.

 
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04-18-17, 05:18 PM   #9  
OSB is oriented strand board, which is used as an exterior sheathing prior to WRB, or weather resistive barrier, or Tyvek being applied, prior to doors and windows being installed. Have you bought your windows yet? If so, do they fit inside the old window frame? If they were bought with that in mind, then don't remove the frame. Cut the sill at the plane of the sheathing. Not the best way to do it, but lemonade time.

 
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04-21-17, 01:31 PM   #10  
Good idea! Yes the window does in fact fit into the frame. That is how I measured the rough opening when I bought it.

 
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04-21-17, 02:15 PM   #11  
Sounds like you measured for a retrofit installation then.

The sill and jambs stay. You cut off the fin by scoring it with a utility knife, then place a blind stop on the jamb (if there isn't one there already). Caulk the blind stop, use a sill expander to fill the gap under the window, put it in.

 
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04-21-17, 03:44 PM   #12  
The only question I have about drilling holes through the frame and screwing it to the existing jambs. Wont that cause the screw heads to protrude in the inside of the frame, causing the windows not to close? Surface needs to be flat in order for them to slide open and closed, right?

 
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04-21-17, 03:58 PM   #13  
The windows will come with a packet of screws and instructions as to where they go. Some even have predrilled holes for you to use. The screws will actually go through the first hole and will hold on the inside hole so the screws won't be visible.

Edit: Scratch that. You are using windows with a flange. You will only fasten the window using the nailing flange, not inside at all.

 
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04-21-17, 04:26 PM   #14  
So that mean's I cant cut the nail flange off and drill screw holes?

 
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04-21-17, 04:56 PM   #15  
Here's the deal. You measured the window. The person who measures and orders the window knows better than anyone how the window is going to be installed. Its pretty hard for us to know how that window should be installed when we can't see it, can't measure it... and can't see or measure the existing opening.

Either my advice in #6 is right, or the advice in #11 is right. Can't say for sure. If you were going to use the nail fin, you shouldn't have measured inside the existing sill and jamb. That's not a rough opening.

We also can't tell you how to install it without seeing it or knowing what it is, as you never specifically said. Is it a single hung like the old one? It's common for some windows to come with a nail fin that can be removed if the window will be installed as as pocket (retrofit) window.

So I don't know where to go from here. Maybe locating the manufacturers installation instructions would be your first step. I have done this for over 25 years, but it's pretty hard to explain every step to you on here if what i have already said isnt making any sense.

 
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