How Thick Should a Barndominium Concrete Slab Be?
Barndominiums have been growing rapidly in popularity for their spacious, flexible and affordable homebuilding potential. But transforming an old barn or shed into a livable residence requires some structural adaptations – starting with an adequately thickened concrete slab foundation.
Typical pole barns or steel sheds build upon dirt, gravel or very thin concrete pads just meant to keep the framing lifted off the ground. Converting these structures to barndominiums demands adding a reinforced slab to withstand occupant loading and anchor the walls. This raises the question – what slab thickness meets structural requirements without overbuilding?
For barndominiums up to 1,500 sq. ft., most recommendations fall between a 4” and 6″ thick slab. This accommodates moderate traffic and furnishings adequately without excessive concrete use. The steel perimeter beams of barndominium kits require less internal slab support than wood framing.
Larger or two-story barndominiums may benefit from 6” to 8” thicknesses to prevent cracking or sinking from heavier live/dead loads. Farmhouses styled for heavy equipment will also need reinforced 8″ slab sections. Maximum steel-framed barndominium size per IRC code reaches 5,000 sq. ft. before requiring special engineering.
Other Slab Spec Factors
Beyond depth, proper steel reinforcement and drainage provisions also play key roles in achieving structural slab integrity:
– #4 rebar grid 12” on center each way
– 4”-6” compacted gravel base
– 6 mil polyethylene vapor barrier
– Wire mesh for added tensile strength
Perimeter edge thickening further helps minimize cracking and separate slabs from exterior grade. Using an elevated floating slab system is another method to prevent moisture wicking and related foundation issues.
In short, 4”-6” offers the ideal balance of strength and economy for small-to-moderate barndominium builds. Evaluate larger footprints on an individual basis to determine if thicker design merits the extra cost. Careful gravel prep, reinforcement and moisture prevention also ensure the slab’s lasting structural stability as an adapted new home.