relative strength of alum vs steel rigid conduit?

keithruckFebruary 2, 2011

I sent a note to a manufacturer but no response, and I haven't been able to find this info online, so I'm hoping maybe someone knows or can point me to some hard data.

I am planning to build a greenhouse structure with rigid pipe, and my local store only carries the steel pipe. I see online that there is a cheaper and lighter aluminum rigid pipe, but no data on how rigid it is compared to steel at the upper end or regular alum conduit on the weak end. Can anyone give me a comparison? Before ordering a bunch of this pipe online I need a comfort level that a hard wind won't bend the structure.

Thanks,

Keith

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petey_racer

You found rigid AL conduit cheaper than steel??? I highly doubt that. It is probably not the same stuff.
Is it actual rigid AL electrical conduit?

    Bookmark   February 3, 2011 at 6:55AM
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brickeyee

Aluminum pipe of the same dimensions will be slightly weaker than steel.

You cannot use just any pipe though, it has to actually be listed (UL is a common listing body).

    Bookmark   February 3, 2011 at 8:27AM
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hexus

"You cannot use just any pipe though, it has to actually be listed (UL is a common listing body)."

I seriously doubt he's going to find any conduit that's listed for use as a structural skeleton for a green house....

    Bookmark   February 3, 2011 at 10:45AM
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fixizin

I seriously doubt he's going to find any conduit that's listed for use as a structural skeleton for a green house....

BINGO!... the OP is on a dangerous path, and needs to pull a whole different catalog, from the shelf of (probably) a whole different supplier... STRUCTURAL steel and aluminum components (and proper CONNECTORS) DO exist... SEEK them out.

Uni-strut probably not listed for primary structural use, but is less off the mark than ELECTRICAL conduit.

    Bookmark   February 4, 2011 at 12:51PM
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keithruck

Actually, using pipe for greenhouses is very common (see he garden greenhouse forum for many examples). The use of rigid is important due to the more secure screw-on connectors, as opposed to regular conduit connectors.
http://www.electriciansupplies.com/product.cfm/p/108312/Conduit---Aluminum-3/4-ALUMINUM.htm is out of stock at the moment, but it is cheaper than the steel I can get locally, and being lighter would make it much easier to assemble. Thanks for the responses,
Keith

    Bookmark   February 4, 2011 at 11:19PM
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brickeyee

Lots of cheap and quick greenhouses have been made from plastic plumbing in 20 foot lengths.

It is flexible enough to be bent into an arch, both ends anchored in the ground, and then plastic sheet used to cover everything.

    Bookmark   February 5, 2011 at 8:48AM
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fixizin

Lots of cheap, quick "structures" have been jury-rigged with all sorts of non-listed materials. Being in a Level 1 HVHZ, this is NOT a luxury I have, legally, practically, or ethically. Excuse my bias, but at least it's in the direction of "overdoing" it.

>>>I'll give the OP credit for at least specifying beefy, OUTdoor-listed RIGID, because over in the sister greenhouse forum he cites, there's peeps using--I am NOT MAKING THIS UP--EMT (thin-wall) conduit for OUTDOOR PRIMARY STRUCTURAL SUPPORTS! HMOG, this stuff's not even listed for merely protecting wires outdoors, let alone for holding up a roof!... but hey, it's galvanized... lol. Cost is always a valid factor, and no sense building to hurricane codes if not necessary. But if you live in an area where such ad-hoc conduit "structures" are common, well then, I guess join the "guild" and have at it, lol.

Regardless of your locale, and lot size, you should at the very least consider what your AHJ, an insurance adjuster, and/or a court of law would say should a blustery thunderstorm or blizzard cause your high sail-area "structure" to topple into, or missile-impact, your residence, or--much worse--SOMEONE ELSE'S. =:O

Bottom line: since the LOAD ("strength") data you're seeking does NOT exist for electrical conduit, you'd always be GUESSING at whether your spans, angles, connections, etc. had adequate SAFETY MARGINS for the task. OTOH there's a plethora of I-beams, T-beams, C-channel, U-channel, square, round, and triangular tubing LISTED for structural use, and a plethora of load tables (and application examples) to go with them. ;')

OK, look... when you're done with this thing... add a (LISTED) steel cable GUY WIRE to each corner!

    Bookmark   February 6, 2011 at 9:46PM
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