I need some wood trim to cover up a 14-1/4" deep xsection of structural wood. 1 x 12 with a 2 x 4 laying over the top + 3/8" plywood. Anyone know where I can get wood trim that's 14-1/4" wide? Nominal 1" thickness x 14-1/4" actual depth . I have a feeling I'll have to get it custom cut or cut 1 x 16" 's myself . I can't even find 1 x 16" 's but haven't looked extensively.

It has hardee plank trim over the structural wood but this is on a deck over a boat slip and the structure walks around a lot with varying soil moisture . The hardee is too brittle and pops off in pieces over time.

I don't quite understand what you're after but what about a marine grade plywood that's ripped to the dimension you need?

All I'm really looking for is decent looking soft wood trim in a 1" thick x 14-1/4 " wide x 8 ft long board. It will be painted. The marine grade plywood may be a viable answer and also probably a somewhat cheaper alternative. Thanks for that suggestion!

I don't know if it is or not. I remember it being expensive when I bought it to redeck my boat but I recall it being dense, heavy, and a nicer finish or better quality than regular treated plywood.

Anyway, outside of that, I'd guess you'd have to get milled wood from the box store which isn't treated, or dimensional lumber you can trim down.

Good luck!