Outdoor Trim Material

[Jerry Solomon]

I have several posts supporting my front porch. Each post has some decorative facing trim on the lower 12". This facing is 1X material about 6" wide. It was originally installed with mitered corners and then painted.

Over the years I have had to replace it more than once due to rotting. In the past I have replaced it with clear pine or fir. It looks nice but tends to rot after a relatively short time in use. I installed it with a gap at the bottom which I filled with caulk to avoid water wicking up from the end. This helped a little but it still rots.

Maybe it's time to change materials. I am considering the following:

1. PT material (yellow-wood)
2. Synthetic lumber (PVC or some other synthetic)
3. Others??

I am concerned about gluing PT material as I have no experience with it.
I am concerned about working with the synthetics as I have no experience with those either.

Any ideas about the best way to solve this problem?

[Peter Quinn]

I did my own porch column wraps with PVC. It looks just like wood, gluing and milling is easy, though its messy stinky stuff to cut and shape, very unpleasant dust that sticks to everything. Get past that and it holds paint exceptionally well, doesn't absorb moisture, mostly stays put. Long lengths will expand and contract as it heats and cools, so you have to attach it well and accommodate the expansion in your design.

As far as the wood, you never want to caulk that bottom intersection. Seal the end grain well, maybe with epoxy as a sealer, leave a heavy 1/8" to 1/4" air gap, include a bug screen, perhaps a vented rain screen approach too. But never caulk that bottom joint. Caulk always fails, and when it does it acts as a dam to hold in water instead of holding it out. Better to use a durable species, keep it well painted and sealed, prime all sides and ends initially, but let it breath and dry out. Failure to do so will lead to coating failure followed shortly by wood failure. Pine and fir are not great choices for full exposure exterior applications. Pressure treat is dead wet when new, you can't really expect a film forming coating like paint to stick to it effectively, the internal moisture is going to shed the paint as it leaves. And by the time its dry enough to paint, the UV exposure has destroyed the lignum in the wood to which your paint will bond, so its never really a great choice for finished millwork. Better to leave PT lumber to deck framing and fence posts.

Cedar is nice, mahogany works well, teak is precious, IPE is durable but more used for deck boards, doesn't like paint so much. They haven't found that holy grail of products that is natural, light, strong, cheap, beautiful and durable. In terms of natural products, its all about the maintenance. So me being a naturally lazy/busy guy, plastic wood suits me fine for many exterior painted trim applications.

[keith micinski]

Look up LP smart side products. It is an OSB product that probably isn't as long lasting as the PVC trim but looks way more like real wood then the PVC does.

[Jason White]

Try a cellular PVC product like Azek, Koma, or Kleer. You can get PVC trimboards in all the common widths and both 3/4 and 5/4 thicknesses. Use a slow curing PVC cement that Azek makes (similar to plumbing cement), or an acrylic-based adhesive called Bond&Fill. I've used PVC trim for years and it's great! Scuff it up with some sandpaper and it paints up nicely, too.


I have several posts supporting my front porch. Each post has some decorative facing trim on the lower 12". This facing is 1X material about 6" wide. It was originally installed with mitered corners and then painted.

Over the years I have had to replace it more than once due to rotting. In the past I have replaced it with clear pine or fir. It looks nice but tends to rot after a relatively short time in use. I installed it with a gap at the bottom which I filled with caulk to avoid water wicking up from the end. This helped a little but it still rots.

Maybe it's time to change materials. I am considering the following:

1. PT material (yellow-wood)
2. Synthetic lumber (PVC or some other synthetic)
3. Others??

I am concerned about gluing PT material as I have no experience with it.
I am concerned about working with the synthetics as I have no experience with those either.

Any ideas about the best way to solve this problem?

[Dan Neuhaus]

We've used a ton of Boral TruExterior trim (about 3 pallets worth milled in t&g siding) and it would be my preference for any painted exterior trim. Its not perfect, but moves much less than PVC and can be painted any color. It takes a miter well and you can fasten at the edge.

[Jerry Solomon]

Thanks to everyone for your responses. Now I have to see which of these materials I can locate in our area (New Orleans)

[Mike Wilkins]

Same problem here with patio posts, with 1X material covering the 4 X 4 posts, rotting over time. Replacing with PVC on the bottom 12" with a router cut edge/base cap on top. Should be permanent.

[Mike Hollingsworth]

Mitered and Glued PVC 10 years ago. I used the blue glue for sprinkler pipe. oil primer then lots of semi gloss latex. no problems whatsoever.
271820

[David Gutierrez]

Was having similar problems and replaced my round porch columns with fiber glass. Look great and they are structural no need for wood that can rot. purchased them through Menards. you might want to look into them.