Framing Glossary: Every Term You’ve Heard But Maybe Never Fully Understood

Framing has its own language.

If you’ve ever walked through a jobsite and heard words like header, LVL, blocking, or shear wall and nodded like you understood, this is for you. We’re going to define the terms, explain them simply, and give you something visual to compare them to so they actually stick.

OSB

Oriented Strand Board

OSB is a structural panel made of compressed wood strands glued together in layers. Think of it like a super engineered sheet of wood chips pressed into a strong board. It is typically used as exterior wall and roof sheathing.

If studs are the ribs of the house, OSB is the skin that stiffens the entire structure.

Plywood

Layered Wood Veneer Panel

Plywood is made from thin layers of wood veneer glued together in alternating grain directions. Imagine stacking sheets of paper but rotating each layer ninety degrees for strength.

It is stronger than solid wood in many directions and resists cracking better than a single plank.

Stud

Vertical Wall Member

A stud is the vertical board inside your walls. Most are spaced 16 inches on center. Think of them as the spine segments of your wall.

They carry weight from the roof down to the foundation.

Top Plate and Bottom Plate

Horizontal Wall Anchors

The bottom plate anchors the wall to the floor. The top plate ties all the studs together at the ceiling.

Picture a ladder laying flat. The plates are the long sides. The studs are the rungs.

Header

Load Bearing Beam Above Openings

A header sits above doors and windows and carries the weight that would otherwise press directly down on the opening.

Think of it like a bridge. It spans across the opening and transfers the load to the studs beside it.

King Stud and Jack Stud

Opening Support System

The king stud runs full height next to an opening. The jack stud sits inside of it and supports the header.

If the header is the bridge, the jack studs are the pillars holding it up.

LVL

Laminated Veneer Lumber

An LVL is an engineered beam made from thin wood veneers glued together under pressure.

Think of it as plywood turned into a beam. It is stronger and more consistent than a solid board of the same size.

PSL

Parallel Strand Lumber

PSL is made from long wood strands bonded together. It handles heavy loads and long spans.

Imagine compressing a bundle of wood fibers into a dense structural column.

Joist

Horizontal Floor Support

Joists support floors and ceilings. They run horizontally between load bearing walls.

If you have ever walked across a room and felt bounce, that feeling is connected to joist spacing and span.

I Joist

Engineered Floor Member

An I joist looks like a steel I beam but is made from wood components with top and bottom flanges and a vertical web.

It allows longer spans with less material and greater consistency.

Rafter

Sloped Roof Member

Rafters run from the ridge of the roof down to the walls and support the roof deck.

Picture the angled bones that form the shape of a pitched roof.

Truss

Pre Engineered Roof Structure

A truss is a factory built triangular framing unit designed to distribute loads efficiently.

Think of it as a pre engineered roof skeleton that drops into place.

Sheathing

Structural Panel Layer

Sheathing attaches to framing to provide rigidity and shear resistance. Without it, walls would wobble under wind loads.

Blocking

Reinforcement Between Members

Blocking consists of short pieces of lumber installed between studs or joists. It prevents twisting and provides support for fixtures, cabinets, or hardware.

Load Bearing Wall

Structural Support Wall

A load bearing wall carries weight from above and transfers it downward. Removing one without reinforcement is like removing a leg from a table.

Shear Wall

Lateral Stability System

A shear wall resists horizontal forces such as wind and seismic pressure. It prevents the house from racking or leaning under stress.

On Center

Measurement From Center to Center

Studs are often spaced 16 inches on center. That means 16 inches from the middle of one stud to the middle of the next. It standardizes strength and material use.

Rim Joist

Perimeter Floor Member

The rim joist caps the ends of floor joists along the exterior wall. It closes the system and ties the floor framing together.

Subfloor

Structural Floor Layer

The subfloor sits on top of the joists and under your finished flooring. It is what actually carries the weight of everything you place inside the room.

— Solara

Understanding the structure changes how you see every project. Knowledge is leverage. Framing is foundation.