How to fix an uneven (curved) upper window box to install blinds

blindsjambsandingwindow frame

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!

Best Answer

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.