How a house is framed from the sill plate to the rafters

House framing is the wooden skeleton that gives a home its shape and strength. A standard platform frame builds the house one level at a time. Each floor creates a flat platform for the walls above it.

Platform framing builds a house level by level

Many homes in the United States use platform framing. The foundation supports the first floor structure, which creates a flat wooden deck. Builders often construct the exterior walls flat on this deck and tilt them up into place. The top of these walls then carries the second floor, which becomes the platform for the next set of walls.

This stacked method has practical benefits over older continuous framing styles. The floor structures interrupt the open wall spaces at each level, which can slow fire moving up inside the walls. It also gives builders a safe, solid surface to stand on while working on the next floor up.

The sill plate, anchor bolts and rim joist

The frame begins exactly where the wood meets the concrete. The sill plate is a flat board, typically a 2x4 or 2x6, usually made of treated lumber to resist rot. It lies flat directly on top of the foundation wall. A foam gasket called a sill sealer often sits between the concrete and the wood to help block air leaks and moisture.

Anchor bolts fasten the sill plate to the concrete. Rules vary as local building departments adopt and amend the International Residential Code, so check with yours. Minnesota's amendment to IRC section R403.1.6 requires sill plate anchor bolts at least 1/2-inch in diameter, spaced no more than 6 feet apart, embedded at least 7 inches in concrete or grouted masonry. The Minnesota rule requires at least two bolts per sill plate section, with one bolt at most 12 inches and at least 7 bolt diameters from each end.

The rim joist forms the outer band of the floor structure. It stands on its narrow edge on top of the sill plate. It runs flush with the outside edge of the foundation wall to box in the floor. The rim joist caps the ends of the floor joists to keep them standing straight under pressure.

Floor joists, beams and the subfloor

Floor joists are the heavy boards that span the open space inside the rim joist. They carry the weight of people, furniture and interior walls down to the foundation. You will typically see 2x8, 2x10 or 2x12 lumber used for floor joists. They stand on edge and run parallel to each other across the basement or crawl space.

A house is usually too wide for a standard joist to reach all the way across. A center beam runs down the middle of the foundation to support the inner ends of the joists. Steel or wooden posts hold this beam up from the basement floor. Understanding this layout helps you see how foundations carry a house from the roof down to the dirt.

Small blocks of wood fit between the joists near the middle of their span. This blocking stops the tall boards from twisting when heavy loads pass overhead.

The subfloor goes directly on top of the joists, using thick plywood or oriented strand board for this layer. These large structural panels often feature a tongue and groove edge so they interlock tightly. Builders apply construction adhesive to the joists and nail the sheets down to prevent floor squeaks. The overlapping wood sheets tie all the joists together into a rigid floor platform.

Wall framing with bottom plates, studs and top plates

The walls stand directly on the subfloor. A standard wood framed wall consists of a bottom plate, vertical studs and a double top plate. The bottom plate is a single horizontal board nailed through the subfloor and into the floor joists below.

Studs are the vertical boards that form the actual wall cavity. The DOE Building America Solution Center says wood framed houses have traditionally been built with 2x4 studs spaced 16 inches on center. The same DOE source notes that in some jurisdictions, particularly hurricane zones, 16 inches on center is the maximum stud spacing allowed, so check with your local code officials. Some interior walls only divide rooms, but others carry load, so have an engineer confirm which is which before any change.

The top plate caps the vertical studs. Builders use two boards stacked on top of each other to make a double top plate. They cut these boards so the top layer overlaps the joints of the bottom layer at the corners. This overlap locks intersecting walls together into a strong continuous box.

Builders cover the outside of the exterior studs with sheathing panels. That sheathing helps the wall resist side loads from wind and earthquakes, and you can learn what shear walls and hold downs do to keep the frame square.

Headers, jack studs and cripples around openings

Windows and doors cut large openings in the wall framing. The roof and floor above those holes still push heavy weight downward. The frame must route that weight safely around the empty space.

A header is a thick, strong beam placed horizontally across the top of the window or door opening. It catches the weight coming down from the top plate and carries it to the sides of the hole. Header size depends on the width of the opening and the load above it, and the building code or an engineer sets it.

Jack studs do the heavy lifting to support the header. They are vertical boards nailed securely against the full height wall studs. Jack studs run from the bottom plate straight up to the underside of the header. King studs are the full height boards that sit right next to the jack studs to keep the assembly straight.

Cripple studs are short pieces of structural wood. They fill the empty space above the header to reach the top plate. They also fill the empty space below a window sill down to the bottom plate. If you plan a home remodel, an engineer must confirm what a wall carries, and the work needs a permit and licensed pros before removing a load bearing wall.

Stacking a second story on the first

A two-story house repeats the entire platform process. The double top plate of the first floor walls acts exactly like the sill plate for the second story.

Builders install another rim joist around the top outer edge of the first floor walls. Second floor joists span across the house and sit flat on those top plates. The joist layout must leave an open hole for the staircase to pass through. Builders use doubled headers and strong trimmer joists around this stair opening to safely interrupt the floor structure.

A second subfloor goes down over the joists to create the upper deck, and the second story walls then stand on this new platform. The load from the second floor transfers straight down through the first floor studs. Builders align the second floor joists directly over the first floor wall studs whenever possible. This direct path moves the weight efficiently down to the foundation.

Ceiling joists, rafters and trusses at the roof

The roof framing rests on the top plates of the highest exterior walls. The roof structure must support the heavy shingles, resist wind uplift and handle heavy snow loads in cold climates. Builders use either traditional stick framing or factory built roof trusses.

In stick framing, builders cut and install ceiling joists and rafters on site. Ceiling joists are horizontal boards that span the top of the house. They create the floor of the attic and give you a surface to attach the drywall for the ceiling below.

Rafters are angled boards that form the slope of the roof. They connect to a central ridge board at the peak and reach down to bear on the exterior walls. The lower ends of the rafters extend past the exterior walls to create the roof overhangs, and a fascia board nails to the very ends to hold the gutters.

The heavy weight of the roof constantly pushes down and outward on the lower ends of the rafters. Ceiling joists often act as rafter ties that hold the outer walls together, so the rafter weight does not spread the walls outward.

Roof trusses offer a different approach. They are wooden triangles assembled in a factory using metal connector plates, and a crane lifts them onto the walls. A single truss replaces both the ceiling joist and the rafters by using smaller pieces of wood engineered to carry loads over long stretches. An engineer designs them, and you should never cut, notch or alter a truss without an engineer's approval.