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Thread: Exterior trime question

  1. #1

    Exterior trime question

    Hi guys,

    I'm in the process of retrimming a few windows on my house. Originally there was just common white pine, and since that's what I'm used to using for soffit and fasica work, I'm going to replace it with the same.

    I know that pine is not the best in terms of resisting rot and poplar is usually a no-no for outside, but my question is how much worse is poplar really than regular pine outside? As I said, I'm used to using pine for exterior trim work, and it's the norm around here (East Coast), but I'm curious if it's any better really than pine in terms of resisting rot, or if it's just cheaper and easier to work with, hence the popularity.

    I have no plans on using poplar, but just curious why it in particular has such a bad reputation compared to pine.

    Thanks,

    Joseph

    p.s. That should read "trim" in the heading (I can't seem to edit that). J

  2. #2
    Join Date
    Jul 2009
    Location
    Mission, Texas
    Posts
    976
    Uhh, half of the houses in the south are sided with Yellow Poplar(AKA Tulip Tree) Even with neglected paint many of these structures are alive and well, if a little shabby looking. Bugs don't like it, sun don't hurt it, and with a good paint schedule it'll probably outlast you. Now if your talking about the 'other, poplar IDK, no experience. Of course I've not worked on any East Coast houses, so I may be talking out of class.
    Mick

  3. #3
    Yeah, I've heard that the poplar down south is better suited. I think it might be a different story, because all the lumber yards up here discourage using their poplar outside.

  4. #4
    Joe,

    Finger Joint Cedar is very popular in NE Fla.

    John

  5. #5
    Join Date
    Feb 2008
    Location
    Northwestern Connecticut
    Posts
    6,249
    Poplar, also Yellow tulip here in New England (not much actual poplar for sale commercially on a wide scale?) is not anybody's first choice here. Out doors it checks, cracks, warps, and mold hits it quick. I think the mold is really the big issue. I have some poplar trim I nailed up in a pinch on my garage just a few years back, and its not looking too good. Its certainly not going to outlast me. It may not last 5 years. Perhaps its the freeze thaw cycle we get here? Not sure, it just doesn't last. There is a heat treated poplar available now, called "torrified" that is supposed to last for exterior use, but I have no experience with that yet. Pine seems to do better than poplar, its lighter, it takes paint well enough, and it nails a whole lot easier. Poplar is a soft hardwood, but it behaves like a hard wood, so it doesn't take nails like pine or cedar. My favorite wood for exterior presently for non human contact trim is plastic. Yup, I prefer the extruded polyurethane stuff from Azek or Kleer. It works well, it holds paint very well, it won't check, warp, rot, bugs can't eat it, and it will definitely outlast me, you, and the next couple of guys. It glues well too. I still prefer wood for things my hands will touch in regular use, like hand rails or stair treads, and porch boards. I really don't like that plastic decking, it gets too darn hot and feels odd to bare feet. But for window trim? Each board I remove from my old house gets replaced with plastic.

    If you do use wood the most important factor in longevity is not allowing moisture to get behind the trim and get trapped. Wet wood needs to dry out. You need to flash the top of the windows, create tight intersections between siding and trim, caulk the sides well to keep out moisture, do not caulk the bottom so it can drain if moisture gets in, etc. Old heart pine was pretty durable naturally, it seemed to have good resistance to bugs weather. But the modern fast growth eastern white variety? Not so good if left unpainted, and if it stays wet, it rots very fast. If you get a cool wet spring like this one with lots of water and many warm sunny days for drying out, it really tests your trim.

  6. #6
    Hi Peter,

    Thanks for the reply. I have a few spots on my house (on a portico) that has poplar crown molding used. It has held up fairly well, though I remember when we repainted it a few years back that we had to stain kill a few black spots. So mold, like you're saying, is probably an issue. But overall, the poplar on these spots looks okay--maybe because we've taken care of it (and it has drip caps, etc.).

    Anyway, the previous flashing and trim was done very poorly. I removed the lower piece of trim on the window, and the plywood wasn't flashed up to the windows, let alone wrapped inside like it should be (with an ice and water shield type material). The tyvek actually stops three or four inches from the window, so now the plywood itself is rotted, and i'll have to removed some of the cedar siding and cut out the ply. Unfortunately, I won't be able to get the new building wrap under the window really, though maybe I can try to tuck it under somewhat. There's a drip cap on top, so that trim was okay. The side trim I haven't removed yet, but I suspsect it wasn't flashed right.

    On the original trim the side casings went all the way down with the bottom trim butted between them. I know this is the usual pattern of boxing out the trim, but I'm think of making the bottom trim run all the way across and adding a bevel to the bottom trim to shed water. Then I'd bevel cut the side trim to lap over the bottom.

    Right now the water just sits on top of the trim, so the bevel (although it might look funky) should help considerably in keeping water from seeping behind. What do you think?

    Joe

  7. #7
    Join Date
    Oct 2009
    Location
    Houston, Texas
    Posts
    243
    If you go with wood trim, be sure to prime it on all four faces and both cut ends before installing. This will extend the useful life considerably.

    I would recommend PVC trim like Azek. However, it expands and contracts over it's length so you must glue and fasten any miters. For longer lengths, use stainless screws and Cortex plugs to cover the holes.

    Water is going to get behind your trim and siding no mater how much caulk you use. That's why flashing details, peel-n-seal membrane, and a water resistant barrier to form an effective drainage plane are essential.

  8. #8
    Oh, sure, flashing correctly is essential. That's why it's beyond me why the builders or whoever installed the windows didn't wrap into the window sills and stopped the tyvec short of the windows.

    John, I'm not familiar with finger jointed cedar for trim, only as siding. Is that what you meant?

    Joe

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