Disaster waiting to happen? Using PVC for deck supports???

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scrumble said something like:

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

What can I say? Filling lolly columns with concrete FOR FIRE SAFETY is part of THE CODE in many places.
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snipped-for-privacy@dog.com wrote:

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=FVFZlqDdM4sC&pg=PA329&lpg=PA329&dq=lally+column+fire+safety+concrete+fill&source=web&ots=3jU1k9nqxm&sig=6Rd3YZxSresrcuXzvSAHE4kxg1w&hl=en#PPA329,M1
Matt
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It probably depends on the diameter of the PVC tube. A 3" or 4" will not have much strength, especially if there is not a continuous large diameter re-bar down the middle. I can see the PVC cracking in cold weather, particularly if the top is able to soak up some water that freezes.
A 6" or 8" PVC tube with three or four re-bars, probably would be no more than a vinyl coated concrete column, and look good compared to bare concrete. The concrete will take most of the load. I can see the same problems with freezing water however. It could be difficult to make a connection with the foundation unless the post is run all the way down to the footing.
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On May 18, 2:02 pm, "Thomas G. Marshall"

I think you're right that there's cause for concern, I think you're wrong about the failure mechanism unless the footings are seriously sub-standard, and I think there's a lot of information left out. The diameter of the PVC, whether it's Schedule 40 or 80 or even the thin stuff that they use for drainage, how deep the footings are, how high above grade the deck is, etc.
R
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On Sun, 18 May 2008 12:36:06 -0700, RicodJour wrote:

If I remember correctly, Schedule 80 is called for on all deck support posts.
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curt said something like:

Implication question: Is PVC meeting schedule-80 requirements considered acceptable for deck supports?
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Ignorance is bliss.
I used PVC for my mail box post. Went down 18 inches, carved out a 3" foot lip, crisscrossed 8" bolt at 6" and 10", filled with concrete and rebar. My mail box was getting knocked down by cars sliding on ice.
Someone was knocking down mail boxes with a baseball bat. The police found him when I told them to check for people with forearms. This clown broke his forearm and his wrist.
But as a deck support, that's a joke.
Dick
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On May 18, 6:17pm, snipped-for-privacy@panix.com (Dick Adams) wrote:

Good thing the clown was dumb as a the post he broke his arm on because if he'd had a lick of smarts at all he would've sued you for the injuries he sustained trying to bash in your mailbox... and he would've won. You're lucky.
A friend of mine put boulders in his front yard because drunk drivers had missed the corner and ended up in his front yard on several occasions, and had hit both his house and his travel trailer at least once. The insurance company gave him 48 hours to have the boulders removed or they'd drop his policy. Long and short of it was, the boulders were a willful admission of wrongdoing/negligence in a lawsuit because they were put there to protect the house from drunk drivers. He could say they were decorative all he wanted, all they had to do in court was point out that the boulders were placed there AFTER the drunk hit his trailer, and he'd lose.
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On May 19, 3:30 pm, snipped-for-privacy@rochester.rr.com wrote:

Well I'm no attorney but, that doesn't sound right. A drunk driver doesn't premeditate getting drunk and running into a house so therefore creates an accident. An idiot smashing mailboxes does premeditate the conditions, planning and carrying out the plan to destroy private property. He could have sued but my bet is that it would have backfired. Lou
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Does that mean that communities have to take down all the guard rails?
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"Thomas G. Marshall" wrote:

There are code approved PVC pipe based deck support columns available. The compressive strength of PVC pipe is tremendous as long as you keep it from buckling. I once tested a 1' length of 4" sch40 PVC pipe in a hydraulic press and it too over 30 tons of force before it started to fail (Enerpac press with pressure gauge). The compressive strength of concrete is also very high. Combined strength is more than adequate and PVC handles cold pretty well also.
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Pete C. wrote:

I'd hardly call it tremendous. 8300 psi exceed most standard concrete, although high strength concrete is available now that substantially exceeds this value. And this falls FAR short of even standard A36 steel.
http://www.harvel.com/piping-clear-pvc.asp
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Matt Whiting wrote:

8300 psi? I come up with more like 37,500 psi since this was 4" dia sch 40 PVC pipe with no filling i.e. 60,000# load on something like 1.6 square inches of PVC total.
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What am I missing here? The extra cost alone makes it not worth doing. Not to mention how you would attach them without making it look jerry rigged. Even if you got past those two items, what would you make the rest of the deck out of to look right? I suppose if your only going 12" off the ground that it wouldn't matter but it sure sounds like your taking a step backwards. Lou
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Pete C. wrote:

Material properties don't depend on the size of the pipe. Did you even open the reference I provided? Do you understand MATERIAL properties?
Matt
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Matt Whiting wrote:

Do you understand that under testing in my 50T press, it took a load of ~37,500 PSI on the 1' length of 4" sch 40 PVC pipe before it failed? Material properties are irrelevant, that was the actual result of the test I noted.
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Pete C. wrote:

37,500 psi is a pressure, not a load. Material properties are not only relevant, they are essential to almost all structural engineering calculations (I know as I have a masters in civil/structural). And the behavior of a short column is MUCH different than a long column. Ever heard of Euler?
A nearly pure compression test (which is what a 1' long 4" pipe comprises) has almost no relevance to the case of a column that has a substantially different slenderness ratio and thus subject to a buckling failure mode as well as possible bending moments due to eccentric loading.
I didn't see a column length in the OP, but when "basement" is the description rather than "crawl space" it is likely that the length is at least 6' and possibly 8' or even more. This is far from being a 1' column. Concrete filled PVC could work if sized properly, but using the same size as the existing steel column is a fool's errand. Again, the OP didn't mention the size of either the steel or the PVC, but I'll bet there were likely nearly the same size. If that is the case, then the PVC is almost certainly inadequate, unless the steel column was grossly oversized for the required load.
Matt
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Matt Whiting wrote:

It is both.

And what I presented was not a structural engineering calculation it was simply the results of a real world test that point out that sch 40 PVC pipe is a lot stronger than most people think.

No kidding, and again, I didn't present any structural engineering info, simply actual results of a real world test showing the surprising strength of PVC pipe.

Right, but again, I didn't present anything to the contrary. I indicated that code approved PVC pipe based deck supports were available, which they are, and an example showing that PVC pipe is stronger than people think.

Probably, and I didn't suggest the OP's scenario was proper or safe. I simply noted that "Using PVC for deck supports" as in the subject line is possible and code approved if done properly, and not a "Disaster waiting to happen" as was also in the subject line. Can't seem to find a link to the product at the moment. Believe I read about it in Fine Homebuilding or perhaps JLC.
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Matt Whiting said something like:
...[snip]...

In my original post I believe I was clear in using the steel column reference only in what the person I met had used as his reasoning for filling them with concrete.
I pointed out that HE was under the impression that the strength of the steel column was primarily the concrete within it, and he believed that the steel was a mere form for it. Hence he figured that using nearly anything as a form, e.g. PVC, would be enough for the deck supports.
I am not sure of the diameter. I am not sure of the length. I am not sure that they were also the footings (though I hope not, since I doubt he understands the notion of "big feet" and I doubt he was using hugely wide posts).
But I have seen concrete cracks in all kinds of things, and I can't help but imagine a crack going clear through one of those things causing a disaster. YMMV
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