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The wood frame around our exterior windows is rotting. Our home is dark brown stained cedar siding, and our window frames are also dark brown. We called a local construction company to fix the old frames, and they said that we can use textured PVC board to replace the rotting wood frame. The PVC board will be white, so we bought a can of acrylic latex for the handyman to paint the PVC frame dark brown (Clark & Kensington premium exterior acrylic latex enamel paint and primer in one). But now (of course, after I purchased the paint), I read that you cannot paint PVC board dark colors! Can anyone tell me what's what with this?

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  • According to google when PVC is painted a dark colour it expands more when in the sun from heat build up. Can cause joints to separate and/or come loose. Seems like if it is attached with better glue/nails/screws might be able to do it, or use different non rotting materials.
    – crip659
    Jun 17 '21 at 10:06
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Due to the increased expansion due to heating from the dark color, you could use the same techniques to attach (or reattach, as the case may be) the PVC trim that is used for screwing down real wood lumber in situations where expansion is likely - do the installation in a way that allows the material to move without causing damage.

For each screw in each board:

  • Remove the screw.
  • Use a drill to enlarge the hole (in the trim board only) to give complete clearance for the screw.
    • Be careful to NOT drill into the wood behind the screw - you still need solid material there for the screw to bite into.
    • The bit should be larger than the diameter of the threads in the screw, but smaller than the diameter of the screw head.
  • Reinstall the screw into the hole leaving the screw head just tight.
    • I'd suggest driving the screw the last couple of turns by hand instead of with a power tool. This will allow you to much more easily feel the point where resistance is increasing and allow you to stop before it's too tight.
    • The screw will be holding the trim very gently against the wall allowing it to move just a bit.
    • This should allow the board to move when it expands due to heat instead of warping.
  • Plug the hole (if desired)

Notes, warnings, caveats:

  • The "one screw at a time" process is based on the assumption that the trim is already installed and caulked in place. If it's not, you could, of course, remove one board, enlarge all the screw holes at once, then reinstall it.
  • I've never tried this so I don't know if it will provide sufficient expansion room for the PVC to move without warping. Your mileage/success may vary.
    • You may consider installing a test piece somewhere on your property that gets a lot of direct sunlight, painting it your desired dark color, and monitoring it for the summer any signs of possible damage.
    • If the results of the test are satisfactory, you can do your painting in the fall or next spring. If they're unsatisfactory, you've not made any permanent changes to your house.
  • This is essentially the exact same method used for installing vinyl siding - nails are driven into slots in the siding and they're to be installed just snug, but not tight.
    • I installed the siding on my garage 26 years ago and have never had issues with siding warping.
    • I've seen newly built houses in a subdivision near us where the siding was nailed too tightly and the siding warped the very first summer.
  • You may have to replace the screws with screws with bigger heads.
    • I've used PVC trim before and the recommended screw is a "trim" screw that comes with a very small head because the small head is easier to hide with a plug.
    • The small head of trim screw may now be (nearly) the same size as your enlarged hole and may not hold very well or at all.
  • Your trim will now be slightly loose against the house.
    • This could cause issues on windy days where the wind could cause the trim to move and rattle.
    • You will have to keep a good eye on your caulking as it's likely that the PVC will be moving much more and that puts more stress on the caulk which could cause it to fail (and the trim to leak water behind it) sooner.
  • I'm sure there are a variety of other possible problems that I've not yet thought of. I'm sure others will chime in with comments about possible flaws with the plan.
    • This is NOT a recommendation to follow this process, it is simply an option if you choose to paint the PVC trim in a dark color that might prevent long term damage.
    • I provide NO warranty of long-term success with this process
    • This may void any manufacturer's warranty because you've not installed it according to their instructions.
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  • Thank you SO much for your thorough response!
    – Annabanana
    Jun 17 '21 at 23:54

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