About House Framing
In wood frame construction, house framing involves the erection of the wood frame’s structural components (studs, rafters, joists) onto which sheetrock, sheathing, roofing and exterior cladding will be installed. Framing is a critical part of the construction process and requires a certain amount of skill. Knowing when to do it yourself or hire the services of a professional is key to the success of your project.
If you're new to framing, you may be able to perform minor interior alterations. But if a room-sized extension is to be added, or if a load-bearing wall is to be re-positioned or removed, you will want to hire a reputable framing contractor. If the envelope or surface of any enclosed inhabitable space (including in the attic and the basement) is breached during a renovation process, it may be wise to reside at a different location until the opening is sealed. It would not be practical to try and maintain comfortable conditions within a living space that is exposed to the elements. Interior renovation work is at times awkward and not as easily accessible as in new home construction.
New structural framework integrated into an existing frame must be installed plumb, level and square. A brief description of the structural members and their assembly into a wood frame house is as follows.
Layout and Frame the Walls
First, mark the layout of the floor plan onto either a concrete slab or plywood decking with a chalk line. These lines give the exact location of the bottom plates of the walls to be erected. The walls consist of a 2 by 4 top plate and bottom plate and 2 by 4 studs at 16 inches on center. Each wall is constructed separately with the rough window and door openings in the appropriate locations, and laid out flat in position. They are then tilted upright into place, made plumb and nailed together.
Install the Joists
Next, you will cut the joists to lay flush with the outer surface of the exterior walls and lay them out along the top plates of the erect walls. Joists vary in size from 2 by 6 inches to 2 by 12 inches and usually run parallel to the short overall dimension of the floor plan. Nail the joists on edge to the top plates at 16 inches on center spanning the entire width of the house. If you're going to add another floor, the joists will function as ceiling joists for the lower floor and floor joists for the upper floor. When used as floor joists, install a layer of plywood decking on top of the upright joists.
Install the Ridge Board and Roof Rafters
Rafters also vary in size from 2 by 6 inches to 2 by 12 inches and are cut and assembled to form a wide variety of roof configurations (gabled, hip and shed roofs are a few common types). Install the ridge board (typically 2 by 12) first, setting it up on posts and making level. Then nail the pre-cut rafters in place at the ridge and at the plate. The notched lower ends of the rafters sit on the top plates alongside each joist and usually extend past the exterior wall to provide an overhang. The top end of each rafter is connected to the ridge board to form the roof peak. The angle of the cut at the ridge end and at the notch will determine the pitch of the roof. A roof that slopes upward vertically 6 inches for every 12 inches measured horizontally is said to have a 6-inch pitch. The studs, joists and rafters are all at 16 inches on center and should be made to align so that a continuous load path will be directed into the ground.