pole barn questions

[towmotor]

If you didn't check out the page that Dave cited, a king post truss includes the two "rafters", the bottom chord (ceiling joist), and a vertical post which is positioned at the center of the ceiling joist at it's lower point and at the peak of the roof at it's upper point.
The joints should have plywood "scabs" screwed and glued on both sides.
You can make them "easily" enough by constructing a layout platform (two sheets of plywood end to end over a couple 2x4's laid flat) upon which you can fasten positioning blocks which will hold the truss components in their proper position for fastening.
If that sounds like alot of work?
Let me re-iterate:
A bought (engineered) truss, whether the king post style or the more common "W" style, is as easy as going to the lumberyard (or Lowe's/Home Depot) and asking for a 16 foot truss.
You'll have a truss that is ready-made (you just have to nail/clip them to your walls and trim the tails to your liking) and you KNOW that it will be suitable for a dwelling, which is your end goal.
Making your own will save you too little money, IMO, to justify running the risk of having a building inspector tell you that your roof structure isn't satisfactory because of home made trusses (even if they're good).
This is one of those areas where it doesn't pay to be "penny wise and pound foolish".

 

[GPintheMitten]

Here's a link to a span table. You might want to talk to your building inspector to determine what span tables he uses. They might be different.

http://www.wclib.org/pdfs/SimpSpanTbls.pdf

If you build your own rafters, with a 3 foot rise over 8 feet (half your building width) you will have 4.5/12 pitch. Your rafter length looks to be 10'. Looking at the span table document in the above link the diagram is a little blury but it looks like they are saying the span in the table is the horizontal projection (in your case, 8').

From my reading of the spans for over 3/12 pitch, you can use 2x4 16" o.c. in certain species. Note the live and dead load and light roof requirements.

For a 12' tall building at the eaves, I would not use 4x4's. I would either use 4x6's or use 3 laminated 2x6's which would be 4.5 inch x 5.5 actual. It might work to use 2 2x6's field bolted together with glue but again, you are then engineering your own members and who knows what the strength is, but it is probably better than one 4x4. When you place a post that is rectangle (not square) you place the longer dimension so as to make the wall wider. This gives you better wind resistance, making your structure stronger.

I don't know how much you are burying your posts but in Michigan we must bury them 42 inch minimum (below the frost line) and place them on concrete footings at the bottom of the hole. This also gives good anchoring to the post for wind and other loads. You won't have deep frost but you still need to anchor the posts well into the ground. Check with your inspector on this. Seems to me 2 foot deep is too shallow, That means that a 14' is too short, so you'll be buying 16 footer posts. That is heavy, but I did some 14' 4x6's when I was in my 30's but my building was 10' tall at the eaves.

Check the span tables and you'll see what your ceiling rafters must be as well. It appears for a drywall ceiling with NO attic storage, you can use 2x6's to span your building width. I think you should use a span value of 15' 6" considering you have wall widths that will shorten the span. That means you could use a Douglas Fir No. 2 or better 2x6 for the ceiling joists. That does not mean you can use any species 2x6. And you can not use 2x4 ceiling joists.

My advice is price the roof members with rafters and ceiling joists as mentioned above and compare that to pre-built trusses. In an engineered truss, they will likely use a 2x4 bottom chord but the weight of the ceiling is transferred to the top members of the truss.

You can put up a 16' truss by yourself. You put the truss upside down inside you building and lift one side up on top of the wall and then lift the other side up. Then you use a long 2x4 with a rope loop around the top of the truss and flip it around, then secure it with a brace and nail it and move on to the next truss nailing a temporary 2x4 along the tops as you go.

Good luck. Hope this helps.

 

[aj1]

i live way out in the sticks i dont think ill have to deal with an inspector only thing i need is a septic pirmint i dont think they have biulding codes out hear. that table is cool im going to save it. by useing #2 pine im only going 2'-3" over the limit on both the rafters and joist and i know that enginers over do every thing. i was thinking of puting 2 or 3 2x6 together and puting purmibarrier on the part thats in the hole for post. they will be about 4 foot deep i can build them trusses in place useing 2x6 joist and 2x4 rafters. /

 

[towmotor]

Build trusses in place?
That negates one of the advantages of using trusses in the first place-ease of installation.
Take the time to make the layout/assembly platform I described, and you'll make some nice, strong and uniform trusses.
You will be able to re-use all of the materials in your platform elsewhere in your building, so expense should not be a factor.

You can set up the platform on any fairly flat piece of ground, shimming/blocking where needed.

If you're not sure what I'm talking about with this "platform", I can draw one with AutoCad and post it here, in a few days.

 

[Steve C]

i live way out in the sticks i dont think ill have to deal with an inspector only thing i need is a septic pirmint i dont think they have biulding codes out hear. that table is cool im going to save it. by useing #2 pine im only going 2'-3" over the limit on both the rafters and joist and i know that enginers over do every thing. i was thinking of puting 2 or 3 2x6 together and puting purmibarrier on the part thats in the hole for post. they will be about 4 foot deep i can build them trusses in place useing 2x6 joist and 2x4 rafters.

/

If you build your own posts by nailing 2 OR 3- 2x6's together, just make them in 4 or 6 parts, use pressure treated wood for the bottom 4 foot and 6 foot sections and nail on a regular wood for the top 12 foot and 10 foot sections. Use waterproff glue to reinforce the bond.

You may be able to buy treated 4x6 poles for less than the cost to build them. Don't put any wood in the ground that isn't treated. It won't last.

 

[GPintheMitten]

I like building pole structures but the heavy poles are a pain when you're by yourself. That is one of the reasons I like the idea of built up 2x6's for poles. It would also make it easier to get the treated sections positioned accurately because you could place the lower section first brace them and back fill before you nail on the top untreated section, but I think I would go with 3 2x6's for each pole, and stagger the joints of the three by using a 6', and 8' and either a 4' or better a 10'. I would put the shortest of the three in the middle. Then on the next post on the wall I would change which side I had the longest of the 3 sections to avoid a bias. Like Steve C said, use water proof glue and lots of nails. I recommend a framing nail gun for this and nails intended for treated lumber. Using only 2 2x6's I think would introduce a weak point in the structure at the seams with a lot of leverage with a 12' tall wall.

 

[aj1]

how do you post pics?

 

[tommu56]

how do you post pics?

here is a good thread

http://www.tractorbynet.com/forums/photos/107314-photo-posting-how.html


tom

 

[jaquetarr]

Amazon.com: Practical Pole Building Construction: With Plans for Barns, Cabins, & Outbuildings (9780913589168): Leigh Seddon: Books
I got this book several years ago and found it pretty good. Amazon has used ones for $7.
In addition to all the excellent advice on Pole Barns given so far, you might (maybe already have) Googled Pole barns for additional information.
Rgds,
tim

 

[aj1]

This is the way I am wanting to build my pole barn. This is a pole barn my father built about 15 yrs ago. The longest free span is 20' it may be sagging an inch or so in some spots, but not much. This is not the only pole barn like this in my area but the only one i could get pics of.