We've used it on our last two houses with excellent results. Holds paint, indistinguishable from wood, and doesn't rot. You just need to allow for the temperature movement. Our typical annual temp range is -15 to 95.

What is your technique for allowing for movement? Leave a small gap if installed in the cooler weather and then caulk? If installed in the hot weather, come back later and caulk when it separates?

It's going to move back and forth as the seasons change. The only place the movement is evident on our house is in a belt that runs all the way around the house. It needed several 20 ft boards end-to-end across the front. We knew it would move, so did not glue the ends together but rather scarfed the joints and painted the ends the trim color. In winter there is a small gap (1/8-3/16") at the extreme), but not very visible, disguised by having paint on the exposed ends. There's flashing on the top edge and behind the joints to keep the water out of the wall.

Wherever possible you can overlap ends so that movement shows up behind something else. A flexible caulk applied when the weather is cool (~50) seems generally to be working fine with shorter boards like window trim and corner boards.

I don't know if the coefficient of expansion is different for different cPVC products, we used Azek. They spec 1/8" per 18 ft. You definitely don't want to butt it tight if you're installing when it's cold out, it will expand and possibly bulge.

The generic name for this product is "cellular PVC". Long pieces and ones painted a dark color expand more than wood in warm weather or in the sun. There are special paints that claim to reduce the expansion.

You should research traditional cornice returns because few builders know how to make them anymore and it really matters. Use the true Greek classical design or the "poor mans' version but don't use a pork chop. Integrating it with a standard aluminum gutter is the difficult part.

Integrating it with a standard aluminum gutter is the difficult part.

Thanks for the replies. Yeah I am trying to figure how I can incorporate the gutter into the overall design and not make it look weird. I am at a slight disadvantage because the roof has already been framed and there is no room at gable for a crown...it just stops at the top edge of the eave rafter (not sure if I am using the correct terminology). So, I have to figure out if just a flat raked cornice (again, not sure of terminology) is going to work.