18x24 Equipment Pole Building question...

[Super77Guy]

I am planning to build this pole building, but I would like to get input on how I should do the roof, without the use of trusses (too expensive). Here are the specifics about the building.

I am in Western PA where I believe the snow load is 30lb??

Building size: 18'x24'x8' and it will be open on one long side for pulling in the tractors and other equipment...

I am planning on using 4x4 posts on 8' centers since the height is 8' on the long sides.

My main question, is what I should use to build the rafters. The roof will be a 4/12 pitch. I have read on this site where I could place rafters every 8' (maybe double the rafter at each post?) and then use 2x4 purlins on edge, but I'm not sure what size rafter I should use.

I appreciate the help!!

 

[Kyle241]

I personally would have rafters closer together than every 8' as that is a lot of space with little to no support. If you get a decent amount of snow, I would be going a lot closer. For example on my firewood shed, I put 2"x6" every 16" just because we do get a lot of snow and it's 4/12. My guess is you should be going every 2', as 4/12 will hold the snow and I would suggest minimum 2"x6", preferably 2"x8" would be better and of course bigger, the better but more $$.

 

[flusher]

I am planning to build this pole building, but I would like to get input on how I should do the roof, without the use of trusses (too expensive). Here are the specifics about the building.

I am in Western PA where I believe the snow load is 30lb??

Building size: 18'x24'x8' and it will be open on one long side for pulling in the tractors and other equipment...

I am planning on using 4x4 posts on 8' centers since the height is 8' on the long sides.

My main question, is what I should use to build the rafters. The roof will be a 4/12 pitch. I have read on this site where I could place rafters every 8' (maybe double the rafter at each post?) and then use 2x4 purlins on edge, but I'm not sure what size rafter I should use.

I appreciate the help!!

Here's the 20x28 ft shed I built two years ago. The roof is 10 ft sloping to 9 ft in the rear (enclosed side).



The posts are pressure treated 4x6s, the beams are doubled 2x12s, the rafters are 2x8s on 16" centers, the girts and purlins are 2x4s. The metal siding is 29 ga R-panel.



I used Behr solid wood stain (redwood) and painted the parts before installation (I hate standing on a ladder with a paint brush in my hand).

Good luck.

 

[Storm56]

I would do 4 foot centers at max. Putting the purlins on the jake is certainly stronger, but does not leave any margin for error when screwing down the roof. For those reasons I just standardized on 2 foot centers and put the purlins on the flat, 2 foot centers. I generally overbuild stuff, just feel better about it.

That said I have seen plenty of buildings around here that used 4 foot centers and purlins on the flat at 2 foot centers with no problem. Snow loads here are rated at 40 lb per sq ft, so if that works here, should be fine for your area at 30 lb per sq ft.

 

[kennyd]

Have you actually priced trusses, and compared that to dimensional lumber?

 

[Super77Guy]

I appreciate all the info. I was basing my thoughts of going with 8' rafter spacing on some other threads i have read here, and also on the specs i read stating that a 2x4 on edge can span up to 9' with a 25lb snow load?

Also, I forgot to mention that I am planning on using rough cut Hemlock from the Amish, so all the lumber will be "true" dimensions (a 2x4 will really be 2" x 4").

@Storm56: What you say makes sense. I'm assuming you based this on using 2x6's?

@Kennyd: Yes, I have priced trusses at between $450 and $500, but i haven't decided on how i am going to build the trusses so I don't know the actual costs for building rafters.

Also, if I were to go every 4' with the rafters, what size 2x should I use between the posts that the rafter will rest on?

Thanks again

 

[Mousefield]

We don't get that much snow most years, a few inches last year but the year before 5 ½ ft, that was the most snow since 1996. You need to look at a "worst case scenario" as far as snow load. I built my chicken palace with full dimension lumber milled from fir on our property. Went 16 inch centers on the rafters, full 2" X 6" X 16 ft. On the open shed side is the future home of my tractor. The building is 24 X 28 ft with the coop the closed in 12 X 28 ft. Sure don't want the roof caving in because I under built. From what you are describing I am thinking you need to beef it up some.

 

[Super77Guy]

We don't get that much snow most years, a few inches last year but the year before 5 ½ ft, that was the most snow since 1996. You need to look at a "worst case scenario" as far as snow load. I built my chicken palace with full dimension lumber milled from fir on our property. Went 16 inch centers on the rafters, full 2" X 6" X 16 ft. On the open shed side is the future home of my tractor. The building is 24 X 28 ft with the coop the closed in 12 X 28 ft. Sure don't want the roof caving in because I under built. From what you are describing I am thinking you need to beef it up some.

That's quite the chicken palace!! If I were to go with the rafters on 8' centers (doubled on the posts) I would use 2"x10"x12' for the rafters and then the 2x4's on edge for the purlins. With that said, I'm thinking that I will probably go with 2"x8"x12' on 4' centers since I will be using 2x4 perlins for the steel roof.

 

[Mousefield]

That's quite the chicken palace!! If I were to go with the rafters on 8' centers (doubled on the posts) I would use 2"x10"x12' for the rafters and then the 2x4's on edge for the purlins. With that said, I'm thinking that I will probably go with 2"x8"x12' on 4' centers since I will be using 2x4 perlins for the steel roof.

With a steel roof snow tends to slide off. I have shingles on my building so snow tends to stay on it. I also have a "snow rake" to take off some snow if we get a lot. I'm thinking you should be ok with your latest ideas on the roof although I think I would go 10" if I was spacing them 4ft apart.

 

[Super77Guy]

With a steel roof snow tends to slide off. I have shingles on my building so snow tends to stay on it. I also have a "snow rake" to take off some snow if we get a lot. I'm thinking you should be ok with your latest ideas on the roof.

Mousefield, would that be the 2x10's with purlins on edge, or the 2x8 on 4' centers, that you say would be good? That's one thing that I like about the steel, is that the snow will just slide off...