Pole Barn Purlin Discussion

[JCook5003]

Hello All-

I've read enough about building pole barns now to make my head hurt. I have a few questions about roof purlins between pole barn trusses on 8' centers.

I should preface that when I built a 36x36 horse barn, we spaced posts 12' for a standard stall size. We used a double 2x12 header and used standard 24' garage trusses at 2' O.C. When we applied the roof purlins we laid 2x4's flat every 2 feet. This method I have before and am comfortable with.

HOWEVER, now that I am building my own garage/shop I am interested in using a true pole barn truss every 8' O.C. This has a few advantages to me, one you save all the header expense and labor. Two, a laminated post made of 2x6's would provide a nice "channel" for the truss to sit in for install.

Now the question. Installing the purlins, most of the time I see purlins installed 2x6 on edge, I am not sure how they are attached but they set on top of the truss. I'm assuming they are toenailed in? I cant imagine people running a 7 or 8 inch fastener through the purlin into the truss.

The problem I see with this is when installing the metal roofing, it would be fairly easy to "rack" those over if you're walking on them.

Why not use a purlin hanger with custom cut 2x6 purlins installed between the truss? The hangers could be installed on the ground, all purlins cut at once and then simply laid in and nailed. I think this would provide a much tighter building envelope also.

Am I over simplifying? Something I'm not seeing, I just want to open the discussion on this and see where it goes. I'm trying to learn as much as I can.

 

[jkwilson]

I've never seen 2X6 purlins here. Remember, location is important when asking about building practices. Since you are talking about 8' spacing, I assume you aren't too far north. We do 2X4 purlins that are on edge and nailed through with a 60d ring shank nail. They go up fast and do a good job.

 

[JCook5003]

Location is southwest Virginia.

 

[dmcintosh]

I have never seen trusses 8' OC, but that may be a location issue. Here in DE we usually set trusses 2' or 4' OC and use 2x4 purlins. The building I just had put up follows this - trusses 4' OC and 2x4 purlins.

 

[Treorp55]

We've built a couple kits, and the purlins are 2x4 on edge with 6" spike. Toe nailing would do no good.

 

[Jay W]

My poles are 12' apart with double truss on each pole except single on end walls. Purlins are 2x6s between the trusses with hangers that were installed while still on the ground.

 

[rieferman]

I've never seen 2X6 purlins here. Remember, location is important when asking about building practices. Since you are talking about 8' spacing, I assume you aren't too far north. We do 2X4 purlins that are on edge and nailed through with a 60d ring shank nail. They go up fast and do a good job.

This.

 

[jives]

In planning our own pole barn we came across each of the designs you mentioned. 2 x 6s hung with hangers between the trusses, 2 x 6 on edge on top of the truss and secured with metal clips, and 2 x 4s nailed with large ring-shank nails. Check out the truss/purlin design of Starwood rafters, DandiBuildings, and Eagle Rigid Span. (Google them).

 

[lakeroadster]

The different combinations are literally infinite. As long as it is an engineered structure follow the engineers lead as detailed on the construction drawings.

We are about to break ground on a "Lester" pole building and the trusses are spaced 13' 6" in the area of the barn where there will be a 2 post lift. It uses 2 x 8 purlins on 18" & 24" centers, purlins are nailed between the trusses except at the gable ends of the building, where they sit on top of the end wall trusses.

Hope that helps.
_____
John

 

[JCook5003]

After some research I really am liking steel trusses for several reasons, price being most of it, but also for ease of install and transport of these two piece trusses. I also really like the "scissor" effect it leaves giving me more center height.

I was thinking of using these trusses at 8' on center with the 2x6's they have stamped drawings that state in this configuration these provide 170 mph wind rating and 55psf snow loading.

http://armourmetals.com/pole-barns.html

My only question is how the hell do you close the side walls with the pulins up that high? I've emailed them asking for sidewall framing details.

 

[MagKarl]

My posts are on 12 foot centers, and my purlins are 2x8's in joist hangers. The end trusses are dropped and the purlins run over the top there to make the overhang. It takes a long time but comes out nice.