My wife and I recently purchased a home and needless to say its a disaster zone. I'm somewhat handy (mainly from summer work with contractors and a technical class to build a house in high school) but I have a lot of "voids" in some of my skills. I have enjoyed the site very much so far but now I have a question of my own!
We recently completed installing five new Marvin Integrity Windows in their "All Ultrex" format which is a full fiberglass interior and exterior. We went with new construction windows, removing the old weight pockets and going down the the bare R.O. I completed the exterior trim using AZEK material. I have no experience doing interior trim. As you can see from the photos I need to make my own small jamb extensions which I was originally planning to do with some 1x material. Then I was planning on nailing the window casing through this 1x and into the jambs and then another nail into the stud of the R.O. which I believe is the traditional method of attaching casing.
My question is...has anyone done this on an All Ultrex window? The jamb material is most definitely not wood, but I'm not sure its fiberglass either. If it is fiberglass I'm almost certain I will have to come up with an alternate method, but it appears to be some sort of PVC/Plastic material? I'm just not sure, please see the attached photos! Thank you!