Shed

[Sifu]

Commercial storage shed, steel framed floor, wood framed walls and truss roof. Engineer specifying to anchor the shed floor to a 4" plain concrete slab on grade. I don't see any exceptions eliminating the required 12" depth and width for footings @IBC 1809.4. Frost isn't required based on the size per the exceptions to 1809.5. A turned down monolithic would meet the requirement's, but seems like over-kill. Would you accept the engineer's design?

 

[Devohle']

If no seismic requirements need to be met, I would default to the engineer's design. However, I would talk with the engineer to get the rational and how they are able to avoid the 12 inch requirement.

 

[Sifu]

No seismic considerations, design incorporates gravity and lateral loads.

 

[my250r11]

We still require the 12"x12" footing as a local requirement. Expansive soils all over the area.

 

[e hilton]

Ifvit has a steel framed floor, why does it need a slab?

 

[bill1952]

Is the "engineer" working for the shed kit company? No code disclaimers on their drawing?

 

[steveray]

We accept the engineering all the time for the IRC sheds....My 2 car garage is on a 12" haunched slab.....

 

[mtlogcabin]

Not all slab on grade require a 12 X 12 footing

1808.6.2 Slab-on-ground foundations.
Moments, shears and deflections for use in designing slab-on-ground, mat or raft foundations on expansive soils shall be determined in accordance with WRI/CRSI Design of Slab-on-Ground Foundations or PTI DC 10.5. Using the moments, shears and deflections determined above, nonprestressed slabs-on-ground, mat or raft foundations on expansive soils shall be designed in accordance with WRI/CRSI Design of Slab-on-Ground Foundations and post-tensioned slab-on-ground, mat or raft foundations on expansive soils shall be designed in accordance with PTI DC 10.5. It shall be permitted to analyze and design such slabs by other methods that account for soil-structure interaction, the deformed shape of the soil support, the plate or stiffened plate action of the slab as well as both center lift and edge lift conditions. Such alternative methods shall be rational and the basis for all aspects and parameters of the method shall be available for peer review.

 

[Sifu]

Ifvit has a steel framed floor, why does it need a slab?

That is the design they submitted. Maybe I am over-thinking this. IBC 1808 permits an SOG foundation, and 1907 prescribes them, and 1604.8.2 requires the lateral load design. I am going to look at this as a framed floor on top of a slab-on-grade foundation, with the appropriate design considerations for the imposed loads.

 

[my250r11]

Not all slab on grade require a 12 X 12 footing

1808.6.2 Slab-on-ground foundations.
Moments, shears and deflections for use in designing slab-on-ground, mat or raft foundations on expansive soils shall be determined in accordance with WRI/CRSI Design of Slab-on-Ground Foundations or PTI DC 10.5. Using the moments, shears and deflections determined above, nonprestressed slabs-on-ground, mat or raft foundations on expansive soils shall be designed in accordance with WRI/CRSI Design of Slab-on-Ground Foundations and post-tensioned slab-on-ground, mat or raft foundations on expansive soils shall be designed in accordance with PTI DC 10.5. It shall be permitted to analyze and design such slabs by other methods that account for soil-structure interaction, the deformed shape of the soil support, the plate or stiffened plate action of the slab as well as both center lift and edge lift conditions. Such alternative methods shall be rational and the basis for all aspects and parameters of the method shall be available for peer review.

Yes, agreed. This would require engineering which we would excepted. BUT no one around here want to spend money so we just require the footings. Been that way long before I got here. We also have an adopted engineered design for new home const. with 24" footings.