I installed fiberglass new construction windows 15 years ago on the front of the house. I used finger-jointed casing around the windows that measure about 1-1/2" square to fill the cavity around the window. The tops and sides are pristine, but the bottom pieces are crumbling! The eaves protect all of the upper wall and casing, but the lower wall takes a tremendous beating from rain and sun. Bottom line, I'm looking for a material that will hold up better. Thinking vinyl, but not seeing those dimensions without building it up. Starting to think about some sort of vinyl or composite wood decking that I could rip. Any ideas? thx!

  • What type of siding wood, hardi, brick? Commented Jul 23, 2017 at 16:48
  • fir wood clapboard
    – piton
    Commented Jul 23, 2017 at 17:16
  • Are all corners mitered? Or is the sill done in typical fashion, straight across with the sides butting onto the top of the sill?
    – Jack
    Commented Jul 23, 2017 at 20:35
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    – SDsolar
    Commented Jul 24, 2017 at 5:55
  • @Jack - It's all butt joints. no miters. I would think butt joints would be better, but it's hard for me to make a case either way except for "looks". I'm curious why you ask. thx
    – piton
    Commented Jul 28, 2017 at 16:19

1 Answer 1


Your best choice would be something made from PVC sold in the trim section of any usual big box home improvement store. Or you could use a heavily treated wood like "Armour" wood that has a higher resistance to rot which is also sold in most stores. Also make sure to use proper flashing behind the trim.☺

  • I ended up ordering 2x4 AZEC vinyl and ripped to fit. Very similar characteristics to wood in terms of cutting, screwing, etc. Very happy so far with the material. Hope it lasts a long time!
    – piton
    Commented Aug 11, 2017 at 3:55

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