12" Tubing for columns?

[TyG]

Hey all, 
   I've been asked to estimate a project. A house has 6  16' square columns that are 12"x12".  I've been googling the various column companies out there.
   BUT, for a simple square, is there a fiberglass or PVC or composite product that I could buy by length? I've been looking up square tubing, box section, etc. There has to be some oddball product for industrial use that is about 12"x12" and in tube form.
   NOTE: the columns are NOT load bearing. There are overhanging trusses, so they are basically decorative columns.
I could possible live with 10" x 10" too.

[Willyou]

Can you make them yourself out of wood? The 16' length might be a challenge, but a decorative feature at the joint might work. Or, maybe it is possible to special order some 16' lengths of your lumber of choice.

[Stwood_]

I googled for 10-15 minutes looking for 12x12 pvc tubing and in that size, all that came up was steel tubing in square. Plenty of round pvc out there.

[MstrCarpenter]

I build porch columns (and wraps) with four boards of equal width (usually PVC). For a 12" x 12" post I'll use 4) 3/4" x 11-1/4" (Vs. two at 12" and two at 10-1/2") Smaller posts, like 5-1/2" get a 1/2" beaded radius on one edge and a 9/16" to 5/8" x 1/8" rabbet on the other edge depending on the bead produced with the router. On larger posts the corners (and the screws that hold them together) get covered with a miter-folded outside corner from 1 x 4 PVC.(That's so no cut edges are exposed) Even though they're basic butt joints I still like to mill a shallow rabbet to keep things flush during assembly.

A few pointers. PVC cement, even Azek glue, takes too long to get hard enough to scrape or sand. I use Christy's White Hot trim adhesive, and/or Bond and Fill. My miter folds are done a router table with a stock feeder, with 12' infeed and outfeed extensions. I still need a helper to manage 16' -18' PVC, and you'll have to order the 90° cutter large enough to cut 31/32" deep. On each corner, when I've milled my second (final) pass, I work right there on the long router table. Clear the dust. Apply adhesive. Fold and tape. Now it's strong enough to move and start the next one. 

At 16' tall, the boxes are strong enough to stay together, but I would consider adding timber strand lumber to the inside corners to keep them straight over time. If you're doing wood, I suggest the same methods including glueing the outside corners together before attaching them.

[Dave Crow]

Could you use something like this company makes?

https://www.foamfactory.com/foam-columns.html