Material Recommendation for Continuous Support Under Vinyl Windows
KCGoodwin
| Posted in General Questions on
I’m installing Milgard vinyl windows and sliding doors into new construction, red iron framed. They require a continuous support under the base, which is often done in cedar.
I’m looking for other options than wood. For other windows, I’ve used Trex decking which we ripped into the right thickness. It’s a pain and there is a lot of waste left over due to the irregular shape of the composite decking material. A Milgard rep suggested I try some of the composite fencing types out there, as they already come cut in sizes near a half inch.
What are other people using?
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Replies
PVC trim? Boral TruExterior trim?
I thought of PVC trim, but it has barely any compression strength. At least the stuff for indoor use doesn't.... But maybe there is PC trim for outdoor use that is firmer? Thank you for the ideas.
Please keep ideas coming - I'm still trying to find something I can get in my remote location. Thanks.
Kim, cellular PVC meant for exterior use, such as Azek, has decent compressive strength, about 1,000 psi for 1/2" thick material: https://www.jlconline.com/how-to/framing/q-a-compressive-strength-of-cellular-pvc-trim_o. I don't like using it under heavy point loads such as beams, though others do, but it's certainly strong enough to put under windows. Boral TruExterior is comparable but it's easier to work with and has a fly ash additive that makes it a more environmentally responsible choice.
Thank you so much for that info. This should work!
When you say "continuous support" it seems like you're referring to the subsill. I would always install flashing over top of that so why not use wood (e.g. split cedar?) then use composite shims to support the window frame out near the corners? I've not used Milgard, but this is manufacturer recommended practice with most residential windows.
I have a mold allergy, and have found wood very problematic especially when trapped against a solid surface (Often can create a place for moisture to build up). Your idea is a good one though, and I see how that could be done carefully and probably not ever mold.
However, we are just so burnt out on wood and remodeling and fixing unexpected moldy problems that we don't want any wood inside our walls at all. My husband and I lost our ability to live in our first house to a severe mold problem, and it made us hypersensitized to mold. We have since remodeled two homes, and in taking them apart one can really learn a lot about what not to do from a mold perspective.
Thanks for your thoughts, though. I appreciated the ideas.