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

Matt Whiting

wrote:
On Wed, 21 May 2008 21:18:25 GMT, "Thomas G. Marshall"
. com wrote:

scrumble said something like:
wrote:
On Sun, 18 May 2008 18:28:11 -0400, Matt Whiting
wrote:
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.

Yes, buckling that would be caused by the heat of a FIRE.

But surely if that was the only reason for the concrete it would far
easier and cheaper just to coat the steel with an intumescent paint?
I agree, but further, this is an odd "argument".

I look also at the things that might happen in a basement. Heavy things
could be moved around and dent the column. It would take a hell of a whack
to do that, but it seems to me that filling the thing with concrete is an
incredibly cheap way of ensuring that a column doesn't collapse in such an
[albeit rare] event.

Further, having seen what my 3 1/2 and 1 1/2 year old consider game for
smacking with a rock or hammer, I'm thinking that substantially removing the
notion of disaster with concrete innards is a great idea. And I can imagine
a young person able to swing a sledge hammer thinking it a "funny idea" to
send a shock wave through the house, thinking perhaps that the lolies were
solid steel or somesuch.

What can I say? Filling lolly columns with concrete FOR FIRE SAFETY is part of
THE CODE in many places.

What is a lolly column? Is that anything like a lally column?

What place has this in the fire code?

Here is a reference that clearly states that the main purpose for
filling the columns is strength. And it discusses that the concrete can
actually be detrimental in a fire in certain conditions although it
certainly is beneficial in other conditions.

Bottom line is that filling the columns with concrete is not done
primarily for reasons of fire resistance. It is for strength first and
fire resistance is a nice fringe benefit.

http://books.google.com/books?id=FVF...en#PPA 329,M1

Matt