Garage Floor Slab Design

A 6 inch thick slab weighs only about 75 psf and live loads anything that is not part of the building itself including vehicles typically don t exceed 50 psf in a garage.

Garage floor slab design.

Recommend design process for residential garage floor joists the use of wood members to support a garage floor is a common practice for sloping lots. That means that the soil under a typical garage slab only has to be able to support 125 psf. This creates additional space under the garage that may be used for occupancy. The inspiration for this column came from unexpected comments about a brief mention of garage floor drains in my december 1 2019 askthebuilder newsletter.

Building codes used to stipulate that the floor of an attached garage be four inches lower than the floor level of the house. Garage floor drain ideas time tested technology. Building codes provide minimum standards to support garage applications and should be followed. Standard thickness of the garage floor slab used worldwide is 6 inches.

The rationale for requiring this little step was that it would prevent spilled gasoline gasoline vapors and carbon monoxide from getting inside the house. Today s residential building code does not include this requirement. Thickness of garage floor slab. Old habits die hard.

Depending on the region and the garage plans this slab can be poured on a compacted subgrade which can include sand or gravel. You will also need some type of steel reinforcing in the garage floor slab portion of the design such as 10 gauge wire mesh that is formed in 6 x 6 squares. It comes in rolls about four feet wide and can be laid on top of the crushed rock and pulled up as you pour the slab with a hooking pole to about 1 1 2 below the finished floor surface.