Following are the code requirements and instructions related to floor framing:
• Double joists are required under parallel bearing walls.
• If pipes penetrate floors where double joists are required, the joists must be separated and have full-depth, solid blocks at least every 4′ along their length.
• Bearing for joists must be Ш" minimum on wood or steel, and 3" minimum on concrete or masonry.
• Where joists lap, there must be a minimum lap of 3" or a wood or metal splice of equal strength.
• The ends of joists must be kept from turning by using Ш" full-depth solid blocking or by attaching them to a header, band, rim joist, or adjoining stud.
• Full-depth, solid blocking is required at intermediate supports in IRC seismic design categories D1, D2, and E. (See seismic maps in Chapter 9.)
• Bridging at 8′ O. C. is required only when joists are larger than 2 x 12, and both edges are not held in line, as with plywood floor sheathing and drywall sheathing, or if thicker than
2” nominal.
The “Floor Joists—Anchor or Ledger" illustration below shows how joists framing into girders must be supported by framing anchors or a 2 x 2 or larger ledger.
Engineered wood products, such as I-joists, can be notched according to the manufacturer’s specifications. (See Chapter 8 for more on engineered wood products.)
The “Framing Floor Openings" illustration shows the following code requirements and instructions
related to framing around openings in floors.
• If the header joists are more than 4′, the header joists and trimmer joists should be doubled.
• If the distance from the bearing point of a trimmer joist to the header joist is more than 3′, the trimmer joists should be doubled.
• If the header joist is greater than 6′, hangers must be used.
• If the tail joists are more than 12′, use framing anchors or a 2 x 2 ledger.
The “Seismic Floor Opening Framing" illustration shows what to do if you are building in IRC seismic design categories B, C, D, or E and the opening is greater than 4′ perpendicular to the joists. In such cases, you must provide blocking beyond the headers, and metal ties must be used to connect the headers with the blocks.
Floor Joists—Anchor or Ledger
Joist framed into girder must be supported by framing anchors or 2 x 2 or bigger ledger
Floor Joists—Drilling & Notching Requirements
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Trimmer joist
If header joist is more than 4′, double header joist and double trimmer joist.
Seismic Floor Opening Framing with an Opening Greater than 4′ Perpendicular to the Joists
or
Metal tie 16 ga. x iy2" x (opening width + 4′-0") (1 each side) use 24-16d common nails.
Sheathing to go on top of joists
From the IBC Code; this information is not listed in the IRC.
