Azek trim question for carpenters
I have a question for carpenters experienced in using Azek pvc trim. I am building my own house and learning as I go. I have 2×6 subfascia and am about to put up 5/4 x 8 Azek for fascia boards and 5/4 x 4 Azek for shadow boards/build-outs on top of the fascia. I have been reading about what the best way is to fasten it to account for the expansion/contraction of the material on long runs (I’m in coastal Maine Zone 6), and I have found some old thread comments on FHB from Mike Smith of RI who suggests leaving unglued shiplap style joints in long runs and butt joints for corners. I am using SS trim screws for fasteners and am planning to glue the fascia board to the subfascia with construction adhesive and will fill the screw holes and paint it all. My question is for the shadow board – do I glue/weld it to the fascia with either construction adhesive or Azek glue and treat them as one unit, making the joints in the same places as the fascia board? Or do I not glue it to the fascia/or just construction glue it and treat it as its own unit and stagger the joints away from the fascia joints? Do the smaller boards expand differently than the larger boards? I had planned on a 3 row fastening schedule with the bottom screw only going through the fascia board and the top two screws going into the shadow board and through the fascia board (is that a bad idea?). That leads me to think I should weld or const. glue them together and make the joints in the same places but I don’t want to screw it up! Thanks for any advice!
Generic picture included of shadow board on fascia for reference
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