I'm putting up a small metal building for the first time, it is a 12 X
30. I went to my local metal building supply store, and they
recommended that for my building size I can use a 4x4 14 guage square
tube instead of an I-beam, with one on each corner and two in the
middle. Since I'm not a welder the sales person at the metal building
supply store suggested that I coat the square tubing with a rust
repellent paint and stick them in the ground two feet in concrete,
thereby circumventing putting in a weld plate as a well as an edge
thickened slab. I've done treated wood posts like this but I just
don't know how fast the square tubing can rust in the ground like this.
If you have any experience or knowledge in this area, please let me
know about what you think.
knowledge in this area, please let me know about what you think.
I have observed that when old concrete structures are demolished, the re-bar
always comes out looking new and totally rust free. Does the concrete
provide chemical protection? Concrete structures that are intended to last
for hundreds of years are built with unpainted re-bar. Anyone able to
provide an explanation?
Several inches of concrete will protect the rebar by keeping the water away.
Concrete is somewhat porous but the more concrete there is, the more water
has to work to get through. Building codes usually specify keeping the
rebar inside the form so that 3 or 4 inches of concrete stay between the
rebar and the outside. Where the contractors screw up and the rebar is
exposed or very near the surface it most definitely rusts and the expansion
of the rebar due to rusting will cause the concrete to spall away. If you
drive near construction of new bridges or roadways, notice that most of the
rebar is epoxy coated (usually green) to help with rust prevention.
I just don't know how fast the square tubing can rust in the ground
Fourteen guage tube sounds light to me, for both structural purposes and
the length of time that it takes to rust through. Concrete tends to
retain as well as wick moisture, hence the need for treated sole plates
in 2x4 studs walls. I'd feel better if the posts where galvanized, or
somewhat greater wall thickness. You don't mention where this is
located, climate or ground water conditions. Probably would not be an
issue in the desert.
Why not do it like a house. Foundation with bolts up and on a sole plate. Bolt
on a wood plate - and on top of that a Horz tube. Then stand and weld everything
on top of that.
I'll have to look at mine and maybe take a picture - mine isn't much different
if any from
what I said - and I have 6" reinforced floor with 4 bay doors.
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
Gary Brady wrote:
I looked at a house once with similar steel for the carport supports sunk in
the concrete. They were rusted completely through just above the concrete
after 16 years. And that was the least of the problems with that house!
This is exactly what _must_ happen!
There are temperature differences and water will condense exactly above
the concrete. -> rust
The tube is hollow (wounder! it's a tube!) and you don't reach into for
painting. But you will have the condensed water there the same. Exactly
above the concrete. -> rust.
I would kick that salesperson a painted I-beam (lenght as on stock) into
his <youknowwhere> until it's coming out where his brain is _supposed_
If you use a tube, it is important to drill a hole just above the base
plate (you will use one) so that water can get out.
You also will zink coat it, it is quite cheap.
I'd take the time to do it right the first time. You may get a few
decades from casting the steel into the concrete or you may be screwed
in 5, depending on where water collects and the amout of condensation.
It may be an extreme example but....spill some fertilizer on a damp
floor near a post and what will probably happen in a few years? What
if the dog tends to pee on the outside corner near a post? Stuff like
that happens all the time in most farm shops. Think of the old carports
where a pipe is cast into the concrete: One seems to last forever, and
the next has nothing left but rust. Why risk that any one of yours will
be the one that rusts? There are just too many outside factors involved
to risk it.
I'd weld a proper plate on the bottom of an I beam and do a raised
grouted footing like is done on commercial buildings.
If you do go with casting directly into the concrete, I'd zinc it as was
mentioned by someone else and I'd go thicker than 14 gauge.
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