I’ve never seen what you describe. Lots of building going on here in WA & in my locale I see lots of Hardie Plank cement siding going up with no trim on windows or doors yet. Trim is trim - goes on last.

Thanx! Here's a photo. Seems backwards to me, photo of our current home coming next.

Here is our current home, trim up before siding.

That's what I thought. The Inspector added the painter will not be happy and will need to do a ton of caulking to prevent what you stated. It was addressed with the Builder and all duscussed with the framer, who told us it gives a beautiful 3-D look to the home! Since the TYPE of trim install was not in writing, to save $ for such an extensive change and, as long as everything is plum/true/flush/level, we'll accept it and replace ourselves later as needed 😠

I guess I would think in the case of new windows over older siding the window trim would go last and if done properly no bugs or water get in there to cause any issues. When I google this it seems both ways are okay.I guess it seems to be the easiest way was done.

Yep, the easy way out. And I agree about sealing all the open spaces. It makes me feel like the hard working crews don't have any reason to developing thier skills. BUT, the home is coming along.

Also the trim below the sill doesn’t have a drip so water will get behind the siding. Can’t see the top of the head trim but if there is no cap flashing you’ll be tearing it up eventually so better to do it now.
I would ask the builder why he didn’t follow the window manufacturer’s installation instructions.

Also caulking is intended to fill consistently narrow gaps with a backer rod. The caulk will need to be removed and replaced when it fails.
This is simply builder incompetence not an alternative design choice.

For HardiePlank (lap siding) and HardieTrim (trim boards), there are 2 different products: HZ5 and HZ10:

On both installation instructions for HardieTrim HZ5 and HZ10 (effective September 2019 to current) they specifically say to "leave 1/8" gap between trim and siding" and also "butt to siding - trim openings prior to the installation of siding".

On both installation instructions for HardiePlank HZ5 (effective September 2019 to current) and HZ10 (effective December 2019 to current) they say to "leave appropriate gap between planks and trim, then caulk".

So in general both products' instructions call for trim to be installed over the wall first and lap siding to butt up against it.

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The region specific products and dates are important to note in that they both mirror the same method of installation.

Important because, on the previous intructions for HardiePlank HZ5 (effective April 2018 now superceded), they noted that trim is NOT to be installed over the lap siding.

This note has been removed on the current instructions, and HardiePlank HZ10 did not have that note to begin with.

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Conclusion? Unclear and unknown why the change. For HZ10 in 2018 you could backhandedly install trim over siding, but not for HZ5. In 2020, in a backhanded way of describing methods you may not install trim over siding anytime, anywhere.

Methods of construction are predominantly carried over from word of mouth and familiarity of how it's always been done, right or wrong. Very seldom do contractors look at manufacturer's instructions. The only way to enforce proper methods and warranties, when things are unclear, is to have the contractor provide proof that their method is conforming, or find out directly from the manufacturer yourself on what is proper.

Thanx! I did contact JH, and they responded, with attachment, where the current install instructions show this method is acceptable in HZ10 due to the different environment, mainly humidity. They also stated they would back their warranty. Still don't get it, though it is a common practice here in TX; I've driven through many subdivisions! BUT, it is not quality. I think JH 'allows' it to appease less skillful contractors who do not know how to do it any other way.

Post the instructions, as the HZ10 December 2019 was the most current instructions on their website, and there is no mention of allowing this method. There is just not mention of disallowing this method.

@Alesa Arnett I cannot edit my original post but I do need to amend it. I read

@3onthetree posts & map which caused me to go outside & look at my siding & corners. I was incorrect! The siding on my house is not under the trim but it does butt up against it. Looking at that zone map, I live in zones 6-10 or the white zone on map. My house is Hardieplank. I stand corrected! Not that it makes any difference here, just setting record straight!