Maximum shed size with 4 supports

[jdg81]

Looking to determine the largest shed I can build with only 4 supports, likely 10" sonotubes set below frost line. I'm currently leaning towards and 8' x 12' size with the sonotubes inset around 6" on the 12' run. This leaves me closer to a 10' span in the long direction. Planning on using PTt 2x8's @12" centers for the joist and am happy to go to a double rim in the 12' direction if needed. Main use would be for lawn equipment.

 

[larry4406]

Cantilever over the posts to extend foot print?

 

[mike93lx]

I did an 8x8 on four supports. Double rim all around and it's solid. Three sides are 2x8, one side is 2x10 due to elevation. Joists are 2x6.

Post in thread 'Small shed floor framing' https://www.garagejournal.com/forum/threads/small-shed-floor-framing.505685/post-9832464

 

[cgrutt]

How high off the ground will this be? I'd inset the tubes maybe 18" or so and support each of the joists with a double beam if possible. I think it will give floor much more support esp if the lawn equipment is heavy (tractors/zero turn etc). Shed will need to be elevated a bit though doing it this way. I had a 12x24 on my last house done that way we ran 8 piers for that (four on each side supporting two beams). It was very solid.

 

[rd65]

Is the ground not level? If it is, then, as big as you want right? Pole buildings can be huge. My shed is 12x14 (I think) but it has gravel floor.

 

[rothbard]

Might want to double check if you are constrained by soil bearing. 4x10" sonotubes on their own is like 2 sq ft of bearing on soil. Where I live that's 3k# max bearing on the soil, including the weight of the sonotubes.

When I was looking at using those I was planning on putting bigfoot forms on the bottom.

 

[mike93lx]

Might want to double check if you are constrained by soil bearing. 4x10" sonotubes on their own is like 2 sq ft of bearing on soil. Where I live that's 3k# max bearing on the soil, including the weight of the sonotubes.

When I was looking at using those I was planning on putting bigfoot forms on the bottom.

Great point, I didn't think of that.

Moving up to a 14" tube doubles bearing, but you could also Bell out the bottom of the hole and still use a smaller tube

 

[jdg81]

Might want to double check if you are constrained by soil bearing. 4x10" sonotubes on their own is like 2 sq ft of bearing on soil. Where I live that's 3k# max bearing on the soil, including the weight of the sonotubes.

When I was looking at using those I was planning on putting bigfoot forms on the bottom.

Planning to bell out the holes as much as possible and will leave the sonotube short of the bottom of the hole. Probably not as big as a bigfoot form but hopefully close.

 

[dutchgray]

Size only limited by load bearing on the ground and the allowable span of whatever size timber you use.

 

[Skooterj]

Thinking the area would depend more on the depth of the floor joist and material. 2x6 pine joists, not big. 4x12 steel I-Beams, very big.

 

[ATC]

You can get a 40' shipping container on 4 supports

 

[pima67]

I built an 8x12 set on 3-4 (can't remember) used but good railroad ties. Floor was rim and joist as you show in your diagram. Guy that bought the house because of the shed.