I have installed some vinyl window and will next install the exterior casing.

The exterior of the window has 'accessory grooves' at the edge of the frame, which I don't like the look of. (They are a narrow channel, to which other things can attach).

I'm considering covering them (top and sides, but not bottom) by landing the inner edge of my casing trim onto the face of the frame, rather than butting it up against the edge of the frame. I will then caulk the trim to the frame. I'll leave the weep hole open.

Assuming I never want to use the accessory grooves, is there any reason I should not cover the accessory grooves with the trim?

AFAICT, the manufacturer does not specify that they should not be covered. Instructions

One piece of context: If instead I abut the trim board to the window frame and then attempt to caulk that joint I will likely end up with caulk inside the accessory groove, which will be a pain to clean out.

enter image description here

  • are those for mosquito net/frame install ?
    – Traveler
    Sep 16, 2022 at 2:11
  • 3
    Pictures might help for a correct answer.
    – RetiredATC
    Sep 16, 2022 at 3:04
  • No, it is not OK, they are there for a reason
    – Traveler
    Sep 16, 2022 at 3:49
  • 1
    Do the groove/s have drainage holes/openings? Covering them up can cause problems with retaining water or letting water go behind the trim.
    – crip659
    Sep 16, 2022 at 10:29
  • Your linked instructions (thanks for including that, so many don't) has a picture under "Installation Prerequisites". Including a copy of that picture in your question with an arrow (or two) pointing to what you consider the "accessory groove" would be helpful, since there's nothing in that drawing with that label. I will say anything that fills, covers or blocks the weep hole ID'd in the bottom of the frame will be a bad idea.
    – FreeMan
    Sep 16, 2022 at 12:06

2 Answers 2


It is OK. The whole extrusion is water-tight. Also, if you plan to caulk the trim to the window it's very difficult with that channel in the way. I absolutely would cover them with casing, and I have. Many times on many homes. With nary an issue.

  1. The "accessories" for which the groove is provided, are typically trim-like in nature. Gap fillers, sill extenders, etc. Perhaps you can find an "accessory" that suits your project nicely, and then you won't need casing. But why? If you like your casing and it doesn't need the groove for installation, it should cover the groove.

  2. Some windows come with their accessory groove semi-permanently sealed with matching plastic. This is so that it doesn't fill with dirt if you don't use it. Some come with removeable covers. Yours apparently comes exposed. The point is, the groove is there for when your trim needs it. Your trim doesn't need it.

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