Framing

Framing lumber dimensions The actual size of a 2”x4” piece of lumber is 1 ½”x3 ½”. 2”x6” -- 1 ½”x5 ½” 2”x8” -- 1 ½”x7 ¼” 2”x10” -- 1 ½”x9 ¼” 2”x12” -- 1 ½”x11 ¼”

Nail Sizes

Termite Shields Metal termite shields are required in many parts of the United States.

Termite Map

Balloon Framing In balloon framing, now seldom used, the studs are continuous from the sill to the rafter plate. Ends of the second floor joists are supported on a ribbon. They are spiked to the stud as well.

Platform Framing Most modern residential and light construction uses platform framing. The first floor is built on top of the foundation wall as though it was a platform. It provides a work area for assembling and raising wall sections safely and accurately. Wall sections are one story high. Outside walls and interior partitions support platforms for upper stories. 

Engineered Lumber

Girders and Beams Girders, also called beams, resting on the foundation walls and on posts or columns, provide the needed support for the floor joists.

Steel Beams In many localities, steel beams are used instead of wood girders. Sizes depend on the load. The load is calculated in the same way as for wood girders.

Joists Floor joints are framing members that carry the weight of the floor between the sills and girders. The most common spacing of wooden joists is 16” O.C. (on center).

Double Floor Joists Joists must be doubled around openings in the floor frame for stairways, chimneys, and fireplaces. The two joists running parallel with the regular joists are called double trimmers. The two joists running perpendicular to the regular joists are called double headers.

Floor Joist System Floor joists must also be doubled when supporting an interior wall running parallel to the joists. Two methods are shown below.

Joist Hangers Metal joist hangers are used for support when joists are not supported by a wall or beam below.

Laying out Floor Joists Floor joists are placed 16” on center.

Floor Joist Layout

Floor Joist Layout

Floor Joist Layout

Butting Floor Joist When butting floor joists over the beam, 2” lumber of the same width and at least 24” long must be nailed to the joists.

Bridging Bridging is composed of pieces of lumber set diagonally between the joists to form an “X”. Solid bridging is also called blocking.

Bridging Place the bridging at the halfway point of the joist span. Use a chalk line for even placement.

Solid-web Floor Trusses A manufactured type of solid-web floor trusses generally called wood I-beams and are used in place of traditional framing lumber. The main advantage of using floor trusses is greater span distance and they also are more stable which reduces squeaky floors.

Subfloors The laying of the subfloor is the final step in completing the floor frame.

Sub floor In most modern construction, ¾” tongue and groove plywood or oriented strand board is used for subflooring. Other sheet materials such as composite board, waferboard (also called waferwood), oriented strand board, and structural particleboard are also approved for use as subflooring.

Subfloor In a glued floor system, the subfloor panels are glued and nailed to the joists.

Studs Most common spacing for studs is 16”. Trimmer studs are shortened studs that stiffen sides of rough openings that bear the direct weight of the header Cripple studs are shortened studs placed below the rough sill or above a header. Pre-cut (regular) studs on an 8’ tall wall are 92 5/8” long.

Headers Headers carry the weight of the building across door and window openings. Header length is equal to the rough opening plus the width of two trimmers.

Two Ways to Build Headers

Partition Wall Headers Smaller 2”x4” headers are used with short cripple studs placed above on non-load bearing partition walls.

Framing Height of Window The rough opening height is measured from the bottom of the header to the top of the rough sill.

Rough Window Sill The rough window sill is nailed to the trimmer studs of the window assembly with short cripple studs as support. The internal cripple studs are nailed in place on the 16” center marks of the wall section.

L-corner Framing Method One method of framing a corner is to build an L channel on the wall that goes all the way to the outside of the floor. This method makes wiring and insulation easier to install.

Partition Supports

Double Top Plates

Plywood Corner Bracing The most widely used method of bracing the outside walls is to use 4’x8’ sheets of plywood or OSB.

Metal-Strip Bracing Another method of bracing exterior walls to resist lateral (sideway) loads is metal-strip bracing.

Wall Sheathing Wall sections should be covered with sheathing before roof framing is started. Sheathing adds rigidity, strength, and some insulating qualities to the wall

House Wrap House wrap comes in 9’ wide rolls and is designed to cover cracks at wall joints where air might enter or leave a building.

Framing with Steel Steel-framed residential construction is increasing in popularity. Metal studs can be used with either metal plates or wood plates.