material for outdoor porch columns

[Zach England]

This is more of a general construction question, so I wasn't sure if it would be appropriate to post in woodworking. The columns holding up the small porch on my 1920 bungalow have failed at the base and are allowing the roof over the porch to slowly slip downwards. I will be replacing them with 6x6 timbers and around those timbers I want to build a truncated column that I will give me a smooth surface for paint and trim work. My neighbor recently had a similar thing done and the contractor who did them used MDF for the outer (non-structural) "shall" around the column and primed them with oil-based kilz. My assumption would be that the mdf would be far too prone to taking up water for any kind of exterior use, no matter how well finished. I'd love to use the mdf becuase it would be a smooth surface, allowing me to apply a textured paint to get the finish I want, but it seems like a less than ideal material. Ideas?

Thanks.

[Dick Strauss]

I think you are right...PVC, high density polyurethane or polymer columns will last longer.

[Neal Clayton]

your neighbor got screwed. his columns will likely fail again in less than 10 years.

are they round or square? if square, why not build them out of a rot resistant wood just like the old ones?

[Zach England]

They will be square and truncated. I do not want to use wood because I'd have to join planks together. I guess this is possible, but seems like another potential point of failure. Also, I can't make these in my shop. It is far too small to cut stuff like this. I need to be able to cut them outside with a handheld circular saw or jig saw and assemble them in place. I believe these traditionally would have been built out of masonry, but that's well beyond my skill set. They will be something like 16 inches wide at the base and 8 inches wide at the top. I might have to take some pictures. This column type was really common in the west on the brick bungalows built in the 20s, but I am not sure it was used in the east so people may not be as familiar with what I am talking about.

Thanks.

Here's a random picture form the web with columns sort of similar to the ones I am trying to build, but mine need to be wider at the base. There are only two.

[Bob Lloyd]

Round or square , you have many options, the man made materials will last longer. I do not know what the contractor used for your neighbor but you can get an exterior MDF. I have never used it though.

[Don Jarvie]

You may want to check with a buiding supply store and not HD or the other. They will have columns made from man made materials all ready to go that will be able to handle the weight of the porch and you just have to paint them.

They will probably cost more than the price of wood but maintence free and will last for years.

[Marcial Morales]

You could use MDO Duraply... very similar to MDF but is used to make exterior signs

[Lee Schierer]

Do a Google search for truncated columns and you will find a number of sources. Here's one (no affiliation) that seems to have exactly what you are looking for.Truncated Columns They make non-structural PVC and Fiberglass columns to order.

[Dan Mages]

You should also look into fiberglass columns. They are structural and available in many shapes and sizes. Since they are fiberglass, the bugs won't eat them and they will never rot. Here is one company that offers them. http://www.hbgcolumns.com/index.php

Dan

[Neal Clayton]

You could use MDO Duraply... very similar to MDF but is used to make exterior signs

sign ink is rated for 5-7 years. i doubt if duraply is engineered to last much longer than that. personally i'd want something a little more substantial on the structure of my house.

in lieu of wood, i'd also recommend the fiberglass/PVC alternatives. they will need to be vented though. the catch with all of the plastic/PVC alternatives to wood is they trap moisture when their joints fail (and they will fail, the sun can kill anything other than rocks and dirt, plastic products expand and contract just like wood).