purlin sizes

[LD1]

I also like Harvs idea that 6 inch purlins would be great for you.

6 in by 2.5 inch 14 gauge purlins weigh about 3.22 lb per foot so since steel is sold by weight they will cost a little over 1/3 of what the 9lb per foot channel someone mentioned will.

You would have to hit those poles with a truck going 50 miles an hour to knock that building down, a little bump is not gonna do it.

Edit: Harvs method on the 8in purlins would be even better overkill.

Reading through some of the other posts, I think there is a little confusion.

The yellow lines in his drawing in post #1 would not be considerd purlins. Thay are the "beams" that I am refering to. They are the ones carrying all the load and the purlins will actuall be ON TOP of these "beams". Those are the only ones I am suggesting using the structural channel on. And they are the only ones that will be comming into contact with the posts as far as roofing is concerned. A 6" 14 guage CEE purlin will NOT be strong enough. It can only carry slightly more than half the load that a 5x9 structural channel peice will.

8" CEE purlin would work, but IMO I would perfer the structural C channel.

For the actual purlins that are spanning 13' on 4' centers, the 4" x 2.5" will do just fine.

As to the walls, I have to agree with harv. The 4" on its side would be the best. The posts are carrying the vertical load, so that is not important, but what is important is the lateral loads from wind. And I like his method of the holes, but that would make construction a bit more difficult.

And as to the cost, Even though 8" CEE that will work for the "beams" is about half the weight per foot, I would bet that it is probabally jsut as expensive. 5" channel Iron is more common and can be bought many more places. That CEE purlin stuff can probabally only be had at building supply places. But this is just speculation, but deffinatally worth price checking before deciding on which route to take.

Good luck with the build, and whatever you choose to do, keep us posted and pleanty of pics.

 

[Eagleview]

I would delete the 4 center posts altogether there is no need for them . I would make trusses out of the pipe you have for the portal and triangular truss' for the roof . Cross Brace the ends and use 6" Z purlins for the roof and 4" purlins for the walls . Z purlins are best as they overlap each other at the joins so are very strong compared to C purlins that butt join .

 

[wroughtn_harv]

Reading through some of the other posts, I think there is a little confusion.

The yellow lines in his drawing in post #1 would not be considerd purlins. Thay are the "beams" that I am refering to. They are the ones carrying all the load and the purlins will actuall be ON TOP of these "beams". Those are the only ones I am suggesting using the structural channel on. And they are the only ones that will be comming into contact with the posts as far as roofing is concerned. A 6" 14 guage CEE purlin will NOT be strong enough. It can only carry slightly more than half the load that a 5x9 structural channel peice will.

8" CEE purlin would work, but IMO I would perfer the structural C channel.

For the actual purlins that are spanning 13' on 4' centers, the 4" x 2.5" will do just fine.

As to the walls, I have to agree with harv. The 4" on its side would be the best. The posts are carrying the vertical load, so that is not important, but what is important is the lateral loads from wind. And I like his method of the holes, but that would make construction a bit more difficult.

And as to the cost, Even though 8" CEE that will work for the "beams" is about half the weight per foot, I would bet that it is probabally jsut as expensive. 5" channel Iron is more common and can be bought many more places. That CEE purlin stuff can probabally only be had at building supply places. But this is just speculation, but deffinatally worth price checking before deciding on which route to take.

Good luck with the build, and whatever you choose to do, keep us posted and pleanty of pics.

You're confusing the paper thin twenty gauge metal stud materials available at box stores with the C purlins we're discussing. They're only available at steel supply stores in the southwest. They're a common building material for building shops and barns.

This morning's price for 8" C purlin is $1.70 a foot. 5" structrual channel is $2.05. What was interesting was the salesman knew the price of the purlin by heart and took about five minutes to get me the price of the structural channel. Greenville Steel, part of Eagle Steel in Dallas, TX.

Another consideration is you can special order structural in forty foot lengths but it's sold in twenty footers. C Purlins on the other hand come in twenties and twenty fives. If you have eight or twelve foot spacing which is common the twenty five foot lengths come in mighty handy.

 

[wroughtn_harv]

I would delete the 4 center posts altogether there is no need for them . I would make trusses out of the pipe you have for the portal and triangular truss' for the roof . Cross Brace the ends and use 6" Z purlins for the roof and 4" purlins for the walls . Z purlins are best as they overlap each other at the joins so are very strong compared to C purlins that butt join .

Z's are common with large sized building construction. Here in the southwest they're a special order item because most of the buildings being built by small contractors and do it yourselfers aren't of sufficient size to use Z's.

Farmers and ranchers have been building barns and sheds the cheapest way possible forever. Here that has been with pipe and purlins. We're now building the same sized barns and shops for the boomer generation and of course, using the same materials and methods.

 

[flusher]

You may remember my thread on I-beams. Well I got a good deal on a semi load of 2 3/8" pipe so my plans on constructing my shed have changed. Instead of trying to make it clear span i have set 16 pipes in the ground to support the structure. I have attached a horrible drawing of what my plan is.

Basically the shed will be 36' wide and 39' feet deep. The pitch is in the 36' direction. With the 16 posts I have set in the ground (black on the drawing) the longest span for the purlin will be 13'. I plan on putting the purlins that the R panels will screw (green on my drawing) to on 4' centers so there will be a purlin centered over the pipes then two suspened in between the pipes by the purlins running in the direction of the pitch (yellow on the drawing).

I am guessing 4" purlins for the green ones will be plenty but I am wondering about the yellow ones if they need to be larger.

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You probably can get some good ideas for your project.