Is pvc or fiber cement trim a better option for long-term durability
MikeonLI
| Posted in General Questions on
Homeowner in Long Island ny. I plan on adding dark colored fiber cement siding to my house and need a dark colored trim.
it seems that fiber cement is a popular siding choice but not a popular choice for rake boards, corner boards, soffit etc. I am not sure if it’s aesthetics or durability.
azek is very popular but must be painted with a special paint if you’re going to choose a dark color. I’m worried about the long term durability of dark azek trim
Any other dark trim options that people have used and have had success with?
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I typically specify and/or use wood. There are a few options that have a rot-resistant treatment and some are naturally rot-resistant. Low up-front carbon emissions, durable, easy to work with. If installed properly the paint should last a long time.
If you must have a synthetic for some reason, TruExterior is a plastic/fly ash composite that is less brittle than fiber cement and moves less than cellular PVC (Azek, e.g.). Miratek is a water-resistant MDF that some builders like; my experience with it wasn't great, but I also never got around to applying a finish coat, just two coats of good primer, and it failed after a few years.
Thanks for the response! We have wood now and it lasted a long time. The problem is that we have lots of trees and woodpeckers and they really damaged the corner boards. So that’s the only reason I don’t want to use wood
I’ll look into the TruExterior. Sounds like a good option. What is the issue with fiber cement trim? It’s just too brittle? I just haven’t found an explanation as to why people don’t like it
I haven't installed fiber cement myself, but I avoid specifying it because of its high global warming impact and because the way most contractors cut it releases a lot of silica, a health issue. I have heard that it's quite brittle and I'm sure that it's heavy, so installing long boards up high would be very challenging. Possible, with enough people and equipment, but not as easy as a lighter-weight, less-brittle material.
Another option is to install a cheap wood base layer and wrap it with sheet metal. It's often considered a low-budget option but if done well, few people can tell the difference between it and solid materials.
Here's an article I wrote on a similar topic, dark siding: https://www.greenbuildingadvisor.com/article/how-to-choose-black-siding.
Great. Thank so much for the information and the link!
PVC, especially a dark-colored PVC, is prone to major thermal expansion and contraction so you would want to detail your corner boards to cover up the edges of the lapboards and leave plenty of room for expansion.
Azek siding has coefficient of linear thermal expansion = 2.58e-5/degF
James Hardie siding = 6.7e-6/degF
Notice the different orders of magnitudes. Azek has 3.85 times more expansion.
Sources:
https://azekexteriors.com/resources/product-education/technical-resources
https://jhinsite.com/wp-content/uploads/2016/09/JH-US-Insite-Expansion-Characteristics-v4.pdf
To put 2.58e-5/degF in perspective, most places swing about 100F from winter to summer. So you'd get 2.58e-3 expansion over the year. That's .00258 or 0.258%. A 16-foot board would expand 0.49 inches, or half an inch.
Thanks. So I guess both you, like matthew25, don’t recommend the pvc trim for dark colors