ACDeGroff

Flat bar for Hoop house?

10 posts in this topic

Hello, 

Long time lurker, first time poster.

   I am currently in the planning phases of my hoop house for my aquaponic setup. It will be 12' x 20' and I am thinking about making it out of 1/4" x 1" x 20' hot rolled steel flat bar.  I saw it suggested on another site as a substitute for rebar.    I'll be anchoring it to a wooden frame with hoop spacing every 4' on center and then adding 4 purlings (also 1/4"x1" flat bar).  I'll then be using bolts with lock nuts/washers to secure the bars at each intersection because I don't know how to weld.  

 

     My only real fear is that I have never worked with steel flat bar and while all of the ratings seem to indicate that it is strong enough I wanted to get someone's input on it as a frame material. It rarely snows where I live but every so often we can get up to 4' will I have a problem with bending? Things like that. Please point out any downsides to my plan because the next step is buying the materials.

 

I included a shot of my sketch up.  It's missing one purlin and the hoops aren't measured on center.  The large tank is half of an old water storage tank that I will line with recycled billboard vinyl. I think I'm going to fill up the green spaces with a rain gutter gravel bed whicking dutch bucket system because I wan't to play with root crops.

 

Thank you,

Alex

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You can't use PVC? PVC is cheap and easily available. Very strong at the right diameter - I think. 

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Flat will not be much good at all, there is very little structural rigidity and there are lots of sharp edges.

 

As Cecil says PVC is good option UV stabilised if you can find it. Drive a long peg in the ground and thread the end of the pipe over it, that gives the wall more support.

 

A ridge beam of 2" PVC down the centre (on top of the hoop) will prevent the middle caving in. perhaps screw it on with a screw with a chunky thread like a plasterboard screw (predrill the hole a little undersized) and a couple of large high quality cable ties crossing each join.

 

if wind is going to be a problem some fencing wire can be used to cross brace the hoop walls to the ends and tension it up.

 

If you want to use steel for hoops, thin walled galvanised pipe or square tube is a better material than flat or rebar.

 

some options to think about anyway. cheers yahoo

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Flat bar is actually just a little more than the large diameter PVC and I thought it might be stronger/longer lasting, but based on the replies I guess I'll just stick with PVC. Thanks to both of you.

Edited by ACDeGroff (see edit history)

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If you want to use steel for hoops, thin walled galvanised pipe or square tube is a better material than flat or rebar.

 

 

By thin walled galvanized are you talking about the metal conduit that's used for electrical? 

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hoop bending

 

there is a video on this page that explains how to work the steel into a curve. Far easier to watch this than have me try and explain it to you. It will be sold as tube (not pipe)

 

zinc plated steel has a "stiffness" that needs to be broken for it to curve without kinking, so it needs to be bent over a template like this or rolled into shape.

 

You will no doubt also notice that there is a swedged end on each length of tube and one slips inside the next (you cant do this with cruddy old water pipe cos there is a raised seam inside)

 

build a greenhouse with top rail fencing material and save money

 

most salesmen have no clue what they are selling so it can be worthwhile taking some cheap vernier calipers and a tape measure and carefully CHECK wall thickness diameter and length. If you want it to last 16 gauge, 0.065" wall thickness will be stronger and have a heavier coating of galvanizing on it for about the same money. but you may have to do a bit of searching to find it

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Yeah, I was actually watching that hoop bending stuff earlier. Thanks for the info on what to look for when purchasing the galvanized pipe.  Going to price out this and a pvc option and go from there.  

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It has been a good discussion, it has got me thinking I better get the finger out and build something to hang my 50% shadecloth on, the summer is getting here all to fast.

 

I think I will roll some steel tube hoops and make a 20 ft wide tunnel. If i cant find someone to swage an end for me I will probably just use some smaller diameter tube and tex screws as a joining sleeve.

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