DIYbanter - View Single Post - Disaster waiting to happen? Using PVC for deck supports???

Matt Whiting

wrote:
On Sun, 18 May 2008 18:02:54 GMT, "Thomas G. Marshall"
. com wrote:

There was a person I was speaking to recently who was proud of what he
considered to be a very bright move on his part.

He had noticed that the lolly-columns in his basement had been filled with
cement prior to being used. He assumed that the strength of the support was
in the cement, and therefore concluded it was a good idea to try filling PVC
tubes and using those as posts (note-not as sonno-tubes, but as fully
structural support posts).

I pointed out that I thought that the strength of a lolly was in the steel,
and that the cement was there merely to ensure that it was never dented,
causing it to fold like an aluminum can. I was concerned that the first
major frost heave under his deck that is able to stress the ledger enough to
pull outward a small amount would cause his pvc+cement "posts" to break.

Was I right?

The concrete in steel lolly columns is to help keep them from collapsing in a
fire.

It also does provide much improved buckling resistance.

The PVC filled column is a very dumb idea unless an engineer has
computed the capacity of the column and sized it appropriately for the
anticipated loads.

Matt