Stud spacing should be shown on the plans, but it is still good to be familiar with the code limitations. For 2 x 4 studs less than 10 feet tall, the maximum stud spacing is 24" O. C., provided the wall is supporting one floor or a roof and ceiling only. For the support of one floor, a roof, and ceiling, 16" O. C. is the maximum. To support two floors, a roof, and a ceiling with a maximum spacing of 16" O. C. and height of 10′, a minimum of 3 x 4 studs must be used. If studs are 2 x 6, a wall can support one floor, a roof, and ceiling at 24" O. C., or two floors, a roof, and ceiling at 16" O. C. Again, this stud spacing only applies to walls that don’t exceed 101 in height. (See "Stud—Spacing and Size" illustration.)
Cripple walls less than 41 in height should be framed with studs at least as big as those used in the walls above them. If the cripple walls are higher than 41, then the studs need to be at least the size required for supporting an additional floor level (as described in previous paragraph). (See "Foundation Cripple Walls" illustration.)
Double plates are needed on top plates for bearing and exterior walls. The end joints of the top plates and double plates should be offset by at least 48”. The IRC allows a 24” offset at nonstructural interior walls. The end joints need to be nailed with at least eight 16d nails or twelve 3” x 0.131" nails on each side of the joint. A single top plate may be used if the plates are tied together at the joints, intersecting walls, and corners with 3” x 6” galvanized steel plates or the equivalent, and all rafters, joists, or trusses are centered over the studs. (See “Walls, Top and Double Plate" illustration.)
Allowable drilling and notching is different for bearing or exterior walls, and for non-bearing or interior walls. Bearing or exterior walls can be notched up to 25% of the width of the stud and drilled up to 40% of the stud provided that the hole is at least 5/8” away from the edge. With interior non-bearing walls, the percentages are 40% for notches and 60% for drilling. (See “Drilling & Notching Studs, Exterior & Bearing Walls" and “Drilling & Notching Studs, Interior Nonbearing Walls" illustrations later in this chapter.)
Header sizes for exterior and bearing walls should be specified on the plans. For nonbearing walls, a flat 2 x 4 may be used as a header for a maximum of up to 8′ span where the height above the header to the top plate is 24” or less. (See “Header for Nonbearing Walls" illustration later in this chapter.)
Fireblocking refers to material you install to prevent flames from traveling through concealed spaces between areas of a building.
The location of fireblocks is sometimes difficult to understand.
It helps to think of where flames would be able to go. A 1%”- thick piece of wood can create a fireblock. If you place a row of these blocks in a wall, you create
a deterrent for the vertical spread of fire. Vertical and horizontal fireblocks are required in walls at least every 10′. (See “Fireblocking Vertical" and “Fireblocking Horizontal" illustrations later in this chapter.)
In a “party wall" construction, where you have two walls next to each other, you can create a fireblock by installing a stud in the space between the studs in the two adjoining walls. This creates a vertical fireblock. Note that %” gypsum board can also be used to create this type of fireblock.
Fireblocking is required between walls, floors, ceilings, and roofs. Typically, the drywall covering creates this fireblock. If it doesn’t, then fireblocking is needed. Where fireblocking is required behind the ledger, it can be installed at the interconnections of any concealed vertical and horizontal space like that which occurs at soffits, drop ceilings, or cove ceilings. (See “Fireblocking at Interconnections" illustration later in this chapter.)
Stair stringers must be fireblocked at the top and bottom of each run and between studs along the stair stringers if the walls below the stairs are unfinished.
Bored holes cannot be bigger than 40% of stud width.
For 2 x 4 = i3/8" maximum For 2 x 6 = 23/i6 maximum
5/8" minimum between hole and edge of stud
Notch cannot be bigger than 25% of stud depth.
For 2 x 4 = 7/8" maximum For 2 x 6 = 13/8" maximum
With doubled studs, bored hole may be as big as 60% of stud width. No more than two successive studs should be doubled and bored up to 60%.
For 2 x 4 studs = 21/8"
For 2 x 6 studs = 35/i6"
Bored holes cannot be bigger than 60% of stud depth
For 2 x 4 = 2/8" maximum For 2 x 6 = 35/i6" maximum
5/8" minimum between hoi and edge of stud
