pole barn questions

[aj1]

i am planing to build a w16xL40xh12 pole barn over my camper and slowly finish it in to a house over time then pull the camper out. im going to use 4x4 post 8' o/c. i think i can go with a 16 foot span useing 2x6x16 joist and 2x4purlins? i dont know if i should put the purlins and joist 2'o/c or 16"o/c? i want to use 3/4 ply wood decking with shingles or maybe i should use 2x8 joist but im on a buget. i just dont want my roof to sag i live in south east texas. no snow im not going to put a lot of slope to the roof. i will have shingles and ply wood on top and later sheet rook on the joist and maybe some a/c duck later. i know that 2x6 will work 2foot o/c with a 16 foot span useing only tin but im going to have decking shingles and later sheet rock. i may have to suthern enginer some trusses lol after all i am a field enginers helper i do basic lay out and off set lines for hi rise buildings should have been a structural enginers helper lol.

 

[HeavyHitch]

I think you should consider a larger post instead of a 4x4. You need to consider wind load on your sidewall. Being 12' and spanning 8' between, I would go with a 6 by at least unless it will be in an area that isn't exposed to any wind.

 

[bobodu]

3/4" roof decking????
Try thinking 7/16" OSB

 

[jcaron2]

3/4" roof decking????
Try thinking 7/16" OSB

I would definitely, definitely NOT use 7/16" OSB. I've seen it used under shingles several times, and after a couple years it always sags and droops under the weight, even at 16" OC. You can stand back away from the roof and easily see where every single rafter or truss is underneath by the way it sags in between. Maybe bobodu has had better luck with it, but I'd spend the little bit extra to get 3/4" T&G OSB. It's about double the price of 7/16", but about half the price of 3/4" plywood. For 20 sheets total, which is what your building should require, you'd be talking about roughly $100 for 7/16" OSB, $200 for 3/4" OSB, and $400 for 3/4" plywood.

As far as the rafters go, if you want to withstand 10 psf live load and 10 psf dead load (the absolute bare minimum IMO), you'll need to use select structural grade 2x6's to make that span, whereas you could get away with No. 1 or No. 2 grade 2x8's. My guess is that #2 2x8s will be your cheapest option.

For posts, I'll definitely agree that 4x4's are too small for a 12' height. If you can't afford 6x6's (and they certainly are a lot more expensive), at least go with 4x6's.

Good luck.

 

[Pops15]

Stay away from the OSB or 3 ply plywood for the roof. Use 1/2" 4 ply or better yet 5/8" plywood.
Consider three 2X6's bolted together for your posts.

 

[bpattie]

definitely go with laminated 2X6 or 8 for the posts. Laminated posts of that size are not only much stronger, but laminated posts will not twist over time as a single post will. The first barn pole building I put up had 8X8's treated and they twisted I bet 10 degrees in spots.

 

[GPintheMitten]

I recommend you go to a lumber yard and see if they have pole barn designs to review. It would give you some more ideas. I agree with laminated 2x6 poles, the bottoms are made from treated lumber and they transition to untreated above the ground.

For purlins, 2x4 would work but they probably will sag in the middle over time and weaken at the ends. If your going to live in this, I would go with 2x6 purlins. Sure you're on a budget but some investment now will pay off down the road. I would also be concerned about a seam in your structure at each pole. Try to get 16 footers and stagger your joints.

Sounds like your are raftering this instead of engineered trusses. If so, you'll need a ridgeboard...don't just try to nail rafters to each other at the peak.

 

[Jay4200]

i am planing to build a w16xL40xh12 pole barn over my camper and slowly finish it in to a house over time then pull the camper out. im going to use 4x4 post 8' o/c. i think i can go with a 16 foot span useing 2x6x16 joist and 2x4purlins? i dont know if i should put the purlins and joist 2'o/c or 16"o/c? i want to use 3/4 ply wood decking with shingles or maybe i should use 2x8 joist but im on a buget. i just dont want my roof to sag i live in south east texas. no snow im not going to put a lot of slope to the roof. i will have shingles and ply wood on top and later sheet rook on the joist and maybe some a/c duck later. i know that 2x6 will work 2foot o/c with a 16 foot span useing only tin but im going to have decking shingles and later sheet rock. i may have to suthern enginer some trusses lol after all i am a field enginers helper i do basic lay out and off set lines for hi rise buildings should have been a structural enginers helper lol.

16' wide isn't enough for a house - make it 24' wide
Use 6x6 posts
Use 2x8 rafters 16" OC and 5/8" plywood with clips - you don't need purlins
You can use 2x4 for ceiling joists - use 2x6 if you ever plan to add insulation
2x4 roof trusses will work fine too

An extra $500 in lumber at the beginning and you'll have a building you can actually keep standing for 100 years.

JayC

 

[GPintheMitten]

When I said purlins, I meant girts. I get them mixed up. Purlins are stringers on roofs, girts are horizontal stringers on walls. You'll need girts but not purlins.

 

[aj1]

ya im not going to use osb of any kind. im going to see if the 1/2in plywood is cheeper than 3/4 that sounds good to me. so 4 2x6 boards bolted together is stonger than 6x6 post? that will be cheeper any way ill bolt them together every 2 foot. i dont think the purlins will weakin on the ends im only going to have 1' 6" over hang i see lots of old homes with 2x4 purlins. im going to use a ridge board and a 2x4 from the ridge doard to the ceiling joist that should keep it from saging in the middle right? the 24x24 sounds good i just dont have the money for that now and i need the foof fast i can allways add on later. now the haveing to use 2x8 or hi dallar 2x6 sucks but ill look in to that. i dont want it to sag or move around and crack all my siding and sheet rook later. thats my new plan what yall think ? i would realy like to use plane old 2x6 joist if i can?

 

[EddieWalker]

I see where some of the companies that specialize in pole barns are going to laminating boards together for their posts. In the few cases where I've seen this, they are attached to a concrete slab. From what I understand, 2x material is not rated for ground contact. It has less chemicals in it then the 4x and larger wood. If you are setting posts in the ground, with or without concrete, I would use wood that is rated for this application.

With youe posts on 8ft centers, be sure to use 2x6's for your purlins. I'd also make sure they were 16ft long and overloap the ends. If you are using metal siding, then every 6 ft would work, but if you are using OSB or plywood for your siding, you need to be have at least 4 ft centers on your purlins, and less if you are installling Hardi Lap Siding over the sheething. If you are thinking of a rock vineer, then 2 ft centers and 3/4 plywood is required.

While I can't speak for areas that get snow, here in the South, 7/16 OSB for roof sheething on 2ft rafters is code and very common. I've seen roofs where you can see the rafters through the shingles, but think that is from other causes. In one case, I saw this on a roof that was shingled when the decking was wet from a rain, and 15 pound paper was used with 3 tab shingles on top. In my opinion, they did everything wrong, and as a result, the roof looks like it. 3/4 plywood on a roof is allot of weight, but it's also allot of money that won't accomplish anything. For those that want to upgrade from OSB, 1/2 inch plywood is just twice as much money as OSB. 3/4 plywood would be about 3 times as much money as OSB. Whatever you use, don't forget the H clips.

Do you know how to build trusses? or will you buy them? From what you've written, it sounds like you are planning on building them. There are some websites that show how to build them. I'd do a search for this and copy the desing for your span and eve design.

While pole barns are very simple to build, what you use is based on what your eventual plan for the building is. If you are thinking of making it into a house one day, then it's important to plan for that now.

Good luck,
Eddie

 

[MarkV]

To me, given that you are not in an area that requires deep footings, I would pour a footing and stick frame. With a pole building that you plan to finish inside and out you add so much wood to support sheathing, siding, sheetrock, windows, ect. that you don't save much with a pole frame. Also I would price out trusses. You may well find them less expensive than roof rafters and ceiling joist type of framing. It would also let you expand the width of the building for a minimal cost which would lend itself to a house structure much better than 16' will. As far as rafter/truss spacing either 16" oc or 24" oc will work depending on the sheathing used. Here if you sheath with 3/4" then 2' on center is fine. If you use 1/2" then 16" on center is required.

MarkV

 

[aj1]

i dont really know how to build trusses i was going to put a 2x4 from the ridge board to the ceiling joist. cant buy prefab trusses i dont have a tractor to pic them up with. im going to use 4x4 post becuase if i get them any bigger i wont be able to handle them. i dont have money for footings or a tractor to dig them with. i will put some X braceing in the walls and maybe ceiling too for the wind. im going to set the post stick frame the roof stick frame the walls and floor. i cant count how many mobile homes 16'x80' i have seen with a pole roof over them using 4x4 post and 2x6 joist with 2x4 raffters 16" o/c. i know that will hold i just havnt seen that many framed out with siding and sheet rock and a wood floor should be just like a stick frame house just a bit taller most homes are 8 foot tall on 3 or 4 cmu blocks and 12 feet at the ridge middle

 

[GPintheMitten]

From your first post, you said 12 foot high, and I assumed you meant 12' at the eaves, but from your last post, maybe you are talking more like 8' at the eaves and 12' at the ridge.

These are major differences as far a wind load. It still sounds to me that you would benefit by looking at some plans or at least sketching some plans and posting them here to get some advice. I have no doubt that once you settle on a good plan, that you will be able to construct it, given your work experience. It just seems that the most help you need is on a good strong design that won't break the bank.

Plans don't have to cost a lot. You could probably find something workable on the internet for free or as mentioned earlier, some ideas from a lumber yard.

 

[aj1]

its going to be 12 foot at the eaves and 15 foot at the rige. no snow so i dont have to make a steap pitch. i will try to sketch something out later. i already got some good info and ideas from you guys. i dont have a tractor yet but i think im going to stick around on this site.

 

[Steve C]

i dont really know how to build trusses i was going to put a 2x4 from the ridge board to the ceiling joist. cant buy prefab trusses i dont have a tractor to pic them up with. im going to use 4x4 post becuase if i get them any bigger i wont be able to handle them. i dont have money for footings or a tractor to dig them with. i will put some X braceing in the walls and maybe ceiling too for the wind. im going to set the post stick frame the roof stick frame the walls and floor. i cant count how many mobile homes 16'x80' i have seen with a pole roof over them using 4x4 post and 2x6 joist with 2x4 raffters 16" o/c. i know that will hold i just havnt seen that many framed out with siding and sheet rock and a wood floor should be just like a stick frame house just a bit taller most homes are 8 foot tall on 3 or 4 cmu blocks and 12 feet at the ridge middle

Even if you used pre built trusses with a span of only 16 foot they would be light enough for you to install yourself without anything more than a good ladder.

I think the 2x4's will work fine for rafters. I have a house here in Northern Michigan that was built in the late 20's. It is 28 foot wide x 38 foot long and it has 2 x 4 rafters on 16" centers. The 2x4 's they used were not long enough so they spliced them end to end with scab plates on the sides. It isn't pretty to look at but it is still standing 80 years later. I have done some extensive remodeling and have reinforced the roof, but even after carrying a northern Michigan snow load for 80 years it had only sagged about 5 inches at mid span in the center of the house. My roof has about a 9-12 pitch so that may have helped. In your climate I would use a 4-12. I have also removed some load bearing walls so I installed a 20" built up beam to carry the weight of the ceiling in the living/dining area. I also jacked up the roof and removed all the sag out of it.

 

[towmotor]

If your trusses are only 16 feet long, then you should be able to make simple king-post trusses, using only 2x4's, and don't bother with a ridge board.

You could have engineered trusses made, and if you're planning to use your building as a dwelling later on, you really should go that route, just so you can avoid trouble with building inspectors.

As far as lifting trusses into position?; You should be able to lift a sixteen footer with one hand.
I installed 20 footers with one other guy on my two story (gambrel) house, so you should be able to do it with no sweat at all.

 

[aj1]

what do kings trusses look like? that may save me money if i dont have to use 2x6 joist i wont need ceiling joist right? the truss will be the joist and the rafters. you guys are right 4x4 post are too small.

 

[dave1949]

what do kings trusses look like? that may save me money if i dont have to use 2x6 joist i wont need ceiling joist right? the truss will be the joist and the rafters. you guys are right 4x4 post are too small.

Check here. About 1/2 way down the 1st page.
en.wikipedia.org/wiki/King_post

The truss takes care of the ridge board, ceiling joists and rafters.

Usually trusses can be ordered at any lumber yard and delivered to your site on their truck.

Dave.

 

[Scotty370]

If your just looking for ideas: Roof - Google Images