The top of my window frame is curved, probably as a fail in construction. Just noticed it when I was trying to install new blinds. You can see it in the picture below that it is uneven by the center of the frame.

Curved frame

Now when I try to install the blinds I need like another quarter inch for the edge to latch into the holder:

Blind does not reach the holder

Is there any simple solution? I can think in adding spacers (which I just did temporarily, but looks quite ugly), or to do some sanding in the center to remove the extra material in the curved part and then repainting.

Edit: Forgot to add that the frame is vinyl.

Thanks a lot!

  • Is the board loose (i.e. can you push it up in the center), or is it firmly attached in that position?
    – FreeMan
    Feb 19, 2021 at 13:35
  • Has it always been bowed like that? Is the board loose? Is the window easily operable? I really hope that's not a result of compression from a foundation or house settling issue because if it is then any "fix" you implement will give way over time.
    – MonkeyZeus
    Feb 19, 2021 at 14:22
  • The board is not loose, it is firmly attached. The window is operable (house was just built).
    – Nando
    Feb 19, 2021 at 15:26

2 Answers 2


This could be an easy fix or a time-consuming one - but worth a shot. With a vinyl window casing I would carefully remove the window trim at the top. That will enable you to see what you're dealing with. If there is a gap in the middle between the window casing and the header you should be able to close it up with a couple of brads. However, The window is almost certainly shimmed. I'm guessing that when they shimmed the window the installer may have over-shimmed at the center point. It's easy to do with a vinyl casing. If so, it's an easy fix. Knock out the shim and insert a narrower one.
If the problem is a warped header then it'll get a lot more complicated requiring removing the casing and sanding or go back to placing a spacer under the brackets.

  • This worked. Builder came and had to remove the trimming and and remove the extra material that was causing the problem behind.
    – Nando
    Apr 8, 2021 at 16:50

I would insert the spacer as you suggest, and then re-trim the front. Sanding 1/4in is a lot of work.

It seems that the casing trim is straight, but the window box is curved. You can get small trims (e.g. pine stop molding) which you could mount to the front face of the box, butting it against the existing casing and against or even in front of the top of the blind frame.

  • Thanks P2000. Forgot to add that the frame is vinyl, would that change the your suggestion?
    – Nando
    Feb 19, 2021 at 1:43
  • You mean the frame of the blinds, right? I have those too. Yes, but the pine/oak trim won't have to cover the vinyl entirely, just a little lip if anything. The point is to cover the gap after you apply the spacers.
    – P2000
    Feb 19, 2021 at 1:49
  • I meant what I called the frame of the window is vinyl. You called it window box, which seems to be the correct name. I noticed it is vinyl when I drilled the holes for the blind holders.
    – Nando
    Feb 19, 2021 at 1:53
  • Ah, well in that case you really can't sand. And the sag is perhaps because the vinyl is under tension. You'd have to remove the box to see what's causing the bending. So, still easiest to the front of it.
    – P2000
    Feb 19, 2021 at 6:07

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