Floor Joists Clearance To Grade

Floor joists girders and posts.

Floor joists clearance to grade.

Scale 1 4 1 is typical size type and spacing of floor joist. So the minimum is 18 for floor joists and 12 for wood beams within the building foundation according to the internaitonal residential code. Clearance between floor joists and the ground minimum 18 inches clearance between the beams and the ground minimum 12 inches clearance between siding and the ground minimum 6 inches floor framing plan. Section r502 10 of the international residential code states that header joists can be the same size as the floor joists when the header joist span isn t greater than 4 feet but if the header joist span is more than 4 feet you ll need to double the header joist and ensure that it s capable of.

Ground clearances some owners and designers might want ground and paving levels that are close to floor levels to avoid having steps between the inside and the outside of a building but this can have a serious effect on material durability and occupant health. Wood siding sheathing and wall framing on the exterior of a building having a. Clearances of less than 0 5 inch 12 7 mm on tops sides and ends. The clearance from grade to the bottom of floor joists in enclosed areas such as crawl spaces under a house is per the crc irc 18 r317 1 location required.

The minimum clearance between the ground and the wood structural floor joists and girders is primarily for prevention of wood rot that is caused by wood being too close to the moisture in the soil. Any reinforcement in slabs on grade must have 2 inches of clearance from soil. Where the header joist span is than 4 trimmer joists and the header joist shall be doubled. Framing of openings require a header and trimmer joists.

Joists have at least 18 clearance to exposed ground and girders have at least 12 clearance. This sample table gives minimum floor joist sizes for joists spaced at 16 inches and 24 inches on center o c for 2 grade lumber with 10 pounds per square foot of dead load and 40 pounds of live load which is typical of normal residential construction. Wood joists or the bottom of a wood structural floor when closer than 18 inches. True floor joist span calculations can only be made by a structural engineer or contractor.

When wood joists or the bottom of wood structural floors without joists are located closer than 18 inches or wood girders are located closer than 12 inches to exposed ground in crawl spaces or unexcavated areas located within the periphery of the building foundation the floor assembly including posts girders joists. If fir sill plates are to be used for interior partitions a vapor barrier of 6 mil visqueen minimum is required.