Shed reference

Walls

A framed wall is a ladder of vertical studs between two horizontal plates, built flat on the deck and then stood up.

Stud

A vertical framing member in a wall, running from the bottom plate to the top plate. Usually 2x4 or 2x6, spaced at a regular interval.

The stud is the unit the rest of the wall is measured against: sheathing lands on studs, and insulation fills the bays between them.

See also on-center, bottom plate, top plate

Bottom plate · also Sole plate, Sill plate

The horizontal member every stud in a wall stands on, nailed down to the floor deck once the wall is raised.

Called a "sill plate" when it sits directly on concrete, in which case it has to be pressure-treated and is usually bolted down rather than nailed.

See also top plate

Top plate

The horizontal member across the top of a wall's studs. Light framing normally uses two courses — a double top plate.

The second course is not redundancy. It laps the corners to tie the walls into a ring, and it bridges the joints in the course below it, so a plate spliced mid-wall is still a continuous beam.

See also cap plate, lap, stud

Cap plate · also Double top plate, Second top plate

The upper of the two top-plate courses. Its joints are deliberately offset from the lower course's, conventionally by about four feet.

Two courses breaking in the same bay make a hinge rather than a beam.

See also top plate, lap

Lap

Where one member runs over another to tie them together — at a corner, one wall's cap plate crosses over the other wall's top plate.

A lap is one board over another. Two boards trying to occupy the same space is an interference, and it is the sort of mistake that looks perfectly convincing in a 3D view because coincident solids render as one.

See also cap plate, corner post

Corner post · also California corner, Three-stud corner

The assembly of studs at the junction of two walls. It has to hold up the corner and also give the inside surface something to fasten to.

A "California corner" does that with two studs plus a short block instead of three solid studs, leaving room for insulation in the corner.

See also stud, lap

Nailer

A stud added off the regular layout, usually nailed flat against another piece, purely so something has wood to fasten to — most often a sheet edge that would otherwise land in a bay.

It is structurally idle. Where an opening's king stud stands close to a layout mark, the mark cannot have a stud of its own without the two boards occupying the same place, so the piece slides tight against the king and catches the sheet edge from there.

See also stud, king stud, layout, sheathing

Blocking

Short pieces let in between studs or joists — to back a sheet edge, to stop a bay from acting as a chimney, or to give something a place to fasten.

See also sheathing

Layout

Where the members go. Layout is arithmetic done once, on the plate, and it is what makes sheet goods land on wood.

On-center · also OC, o.c.

Spacing measured from the centerline of one member to the centerline of the next — 16" on-center, 24" on-center. Not the clear gap between them.

Center-to-center is what makes the arithmetic work: a 4-foot sheet edge falls at 48", which is a whole number of 12", 16", and 24" bays, so the edge lands on the middle of a member and the next sheet lands on the other half of it.

See also layout, sheathing

Layout

The marks on a plate saying where each stud goes, made from one end of the building with a tape run out once.

The first member is flush with the end of the wall, so its center sits half a thickness in — three quarters of an inch for a 2x. Every mark after it is a whole multiple of the spacing from the *building's* corner. Hooking the tape somewhere else instead — the end of one wall's own plate, say — throws every sheet edge off by that much for the length of the building.

See also on-center, sheathing

Bay

The space between two adjacent framing members.

Layout leaves one short bay at the far end, where the run stops dividing evenly. That is correct: the odd bay gives, not the sheet layout.

See also layout

Rough opening · also RO

The hole in the framing a door or window unit sits in — bigger than the unit itself, to leave room to shim it plumb and square.

See also header, king stud, jack stud

Openings

Cutting a hole in a wall interrupts the studs that were carrying load there. Framing an opening is putting that path back.

Header

The beam over an opening, carrying the load the interrupted studs used to carry and delivering it to the studs beside the opening.

Sized by what it spans and what is above it. In 2x wall framing it is often two plies on edge with a spacer between them, so the assembly comes out the thickness of the wall.

See also jack stud, king stud, rough opening

Jack stud · also Trimmer

The shortened stud beside an opening that the header bears on, running from the bottom plate up to the underside of the header.

Jacks are the legs of the beam. Their number goes up with the span the header carries.

See also header, king stud

King stud

The full-height stud immediately outside each jack, running plate to plate and nailed to the jack beside it.

The jack carries the header down; the king keeps the whole assembly from rotating out of the wall and ties it back into the plates.

See also jack stud, header

Cripple stud · also Cripple

A short stud filling the space above a header or below a rough sill, on the same layout the wall's full-height studs use.

It keeps the layout unbroken across the opening, so sheathing above and below the hole still finds framing where it expects to.

See also rough sill, header, layout

Rough sill

The horizontal member forming the bottom of a window's rough opening. Doors have none, because the opening runs to the floor.

See also rough opening, cripple stud

Roof

The roof is where framing stops being rectangles. Every member meets something at an angle, and its ends have to be cut to that angle to bear on it.

Pitch · also Slope

How steep a roof is, given as rise over a 12" run: a "4:12" roof climbs 4 vertical inches for every 12 horizontal.

A ratio rather than an angle, because every cut on the roof is laid out from that ratio with a square — nobody sets a framing square to 18.43°.

See also rafter, plumb cut, seat cut

Rafter

A sloped member running from the ridge down to the wall, carrying the roof sheathing and everything on it.

A rafter's board is longer than the horizontal distance it covers, and longer again than the sloped line it sits on — the angled cuts at each end run diagonally across the stock. Ordering the line length gets you a rafter short at both ends.

See also plumb cut, seat cut, birdsmouth, ridge board

Ridge board

The board at the peak that the rafters from both slopes land against. It is an alignment and nailing surface: with the rafters tied at the bottom it carries almost no load, and it needs no support of its own.

It has to be at least as deep as the cut end of the rafter, which is deeper than the rafter itself — a plumb cut runs diagonally across the stock, so a board only as deep as the rafter leaves part of that cut bearing on nothing. And a ridge board is only honest where rafter ties are doing their job: without them the same piece has to be a ridge beam instead.

See also rafter, plumb cut, ridge beam, rafter tie

Ridge beam

A ridge sized and supported to actually carry half the roof, used when nothing ties the rafter feet together — a cathedral or vaulted ceiling.

It is a beam in the ordinary sense: sized for its span, not spliced, and held up at each end by a post that runs continuously to a foundation. The difference between this and a ridge board is the difference between a roof that hangs from the peak and one that stands as a triangle.

See also ridge board, rafter tie, thrust, post

Rafter tie

A horizontal member joining a pair of opposing rafters near the plate, holding the bottoms of the two slopes together.

It works in tension, resisting the outward thrust — so a fairly small board carries a surprising amount, and its span matters far less than its connections. It is not a ceiling joist and not a floor: an attic you can store things in needs members sized for that, which is a different job.

See also thrust, collar tie, ridge board, top plate

Thrust

The outward push a pitched roof puts on the walls it sits on. The shallower the pitch, the harder it pushes for the same load.

On a gable it has to be resisted by something, and there are only two answers: tie the rafter feet together, or carry the ridge on a beam so the rafters hang rather than lean. Doing neither looks finished and spreads the walls over a few seasons. A lean-to's rafters are the exception: seated level on a wall at each end, they push on neither.

See also rafter tie, ridge beam, pitch, lean-to

Post

A vertical member carrying a concentrated load straight down — under the end of a beam, most often.

The load has to keep going: a post that lands on a floor rather than on something continuous to the ground has moved the problem rather than solved it. Where a door or window is in the way, the post has to land on a header sized for that load rather than for the opening.

See also ridge beam, header, stud

Plumb cut

A cut that stands vertical once the member is installed. A rafter gets one at the ridge, so it bears flat against the ridge board, and usually one at the tail so the fascia has something flat to land on.

Its angle is the roof's pitch, laid out with a square.

See also pitch, rafter, seat cut

Seat cut · also Level cut

The horizontal cut that lies flat on the top plate, carrying the rafter's load into the wall. It is the level half of a birdsmouth.

See also birdsmouth, heel cut, plumb cut

Birdsmouth

The notch cut into the underside of a rafter where it crosses the wall — a level seat cut bearing on the top plate and a plumb heel cut down the outside face of the wall.

Without it a rafter merely touches the outer corner of the plate rather than sitting on it. Cutting one lowers the whole roof by the height of the heel. Convention limits the notch to about a third of the rafter's depth: past that, what is left over the bearing point is no longer the rafter that was sized for the span, so a steep roof on shallow stock takes a narrower seat instead of a deeper notch.

See also seat cut, heel cut, rafter, top plate

Heel cut

The plumb half of a birdsmouth: the vertical cut at the outer face of the wall, from the rafter's underside up to the seat.

See also birdsmouth, seat cut

Rafter tail · also Tail

The part of the rafter that continues past the wall to form the eave overhang.

See also eave, fascia, overhang

Eave

The lower edge of a roof, where it overhangs the wall below it.

See also rafter tail, fascia, rake

Rake

The sloped edge of a roof at a gable end — the edge that climbs from the eave to the peak.

See also gable, eave

Fascia

The board closing the ends of the rafter tails along an eave. The roof edge and a gutter both land on it.

It is what the plumb tail cut is *for*: a square-cut tail leaves a face that is not vertical and nothing flat to nail the fascia to. It also has to be deeper than the rafter's stock, because it covers the rafter's plumb-cut end face.

See also rafter tail, eave, plumb cut

Frieze block · also Bird block, Bird blocking, Eave blocking

The block that fills a rafter bay where the rafters cross the wall, closing the gap between the top plate and the roof sheathing.

Without it every bay is an open slot into the roof space — a couple of inches by the width of the bay, all the way along both eaves — and birds and wasps find it quickly. It also stops the rafters from rolling on their bearing, which is why the code asks for blocking once a rafter gets deep enough for the question to matter. The ventilated version, sold as a vented bird block, doubles as the intake for a vented roof space.

See also blocking, top plate, birdsmouth, rip

Barge rafter · also Fly rafter

The rafter out at the edge of a rake overhang, past the gable wall. It is the board the roof edge and the rake trim land on.

Nothing under it: it bears on no wall, which is why it takes no birdsmouth and why something has to hold it up from the building.

See also rake, outrigger, rafter, birdsmouth

Outrigger · also Lookout, Outlooker

A short piece running out past the gable wall to carry the barge rafter and the rake overhang.

Two ways to frame it. A gable ladder nails the pieces between the gable-end rafter and the barge rafter like rungs, which suits a modest overhang. A true outrigger runs back over the gable rafter to the next rafter in, which carries much more — and needs the gable rafter dropped by the outrigger's thickness so the sheathing still lands flat.

See also barge rafter, rake, gable, blocking

Gable

The triangular section of wall between the two slopes of a roof, at the end of the building.

It is framed with studs of every different length, each cut to the underside of the rafter above it.

See also rake, rafter, lean-to

Lean-to

A roof of one slope across the whole building, rising from a low wall to a high one — also called a shed roof. The two end walls climb with it, and there is no ridge.

Each rafter runs from one wall to the other and takes a birdsmouth at both: down the outside face of the low wall and down the inside face of the high one, which is framed taller by exactly the roof's climb between them. Seated level at both ends, the rafters push on neither wall, so there are no ties to fit. The price is span: a rafter crossing the whole width is twice as long as a gable's, so a lean-to wants deeper rafters and tops out narrower.

See also gable, birdsmouth, thrust, rafter, saltbox

Saltbox

A gable roof with its ridge off the middle: a long slope on one side and a short one on the other, after the New England houses that grew a lean-to down the back.

With both slopes at one pitch, the wall under the short slope is framed taller than the other by the difference in how far each climbs, so the two arrive at the ridge together. The eaves are then at two heights and no rafter tie can run level from one to the other, so the ridge is usually a beam on posts, with its posts standing off the middle of each gable wall.

See also gable, ridge beam, lean-to, rafter tie

Collar tie

A horizontal member connecting a pair of opposing rafters in the upper third of the roof, resisting the ridge being pushed apart under wind uplift.

Not the same as a rafter tie, and not a substitute for one. A tie up in the top third barely resists the walls spreading — the force in it climbs the higher it goes — which is why the two are different members with different names doing different jobs.

See also rafter, ridge board, rafter tie, thrust

Overhang

How far the roof projects past the wall. Measured horizontally, not along the slope.

See also eave, rake, rafter tail

Floor and foundation

What the walls stand on, and what that stands on.

Joist

A horizontal member carrying a floor, spanning between supports and spaced on-center like studs.

See also rim joist, span, on-center

Rim joist · also Band joist

The joist running around the perimeter, closing the ends of the joists and holding them upright.

See also joist

Skid · also Runner

A heavy timber running under the floor frame, spreading the load onto the ground and letting a small building be dragged.

The usual foundation for a shed small enough to be exempt from permitting.

See also joist

Pier block · also Deck block

A precast concrete block set on the ground to carry one bearing point of a floor. A row of them under a beam is a pier foundation.

How far apart they go is a question about the beam over them, not about the blocks: the beam's span is what decides it.

See also floor beam, span

Floor beam

A built-up member spanning between piers and carrying the joists. Built up means several plies of ordinary lumber nailed face to face.

A joint in a beam belongs directly over a bearing point, and the plies are staggered so they never all break in the same place.

See also pier block, joist, span

Slab on grade

A single pour of concrete that is both the foundation and the finished floor. There is no floor frame over it and nothing under it but fill.

See also sill plate

Sill plate · also Mudsill

The flat board a wall bears on where it meets concrete, bolted down into the pour rather than nailed to a floor frame.

Pressure treated, always: untreated lumber against concrete draws moisture and rots from the bottom, where nothing shows until the wall moves.

See also slab on grade, bottom plate, anchor bolt

Anchor bolt

A threaded rod set into wet concrete, left standing proud, and used to bolt the sill plate down once the pour has cured.

Placed close to every end of a plate and at intervals along it. Set them in the wrong place and the plate has to be drilled to match.

See also sill plate

Span

The clear distance a member has to cross between supports. What size a joist or rafter needs to be is a question about span, spacing, and load.

Published span tables answer it. They are the reason a wider building gets deeper joists rather than more of the same ones.

See also joist, rafter

Subfloor · also Deck

The sheet goods laid over the joists, forming the floor surface and tying the frame together.

See also sheathing, joist

Sheet goods and skin

The panels that close the frame in and stiffen it.

Sheathing

Structural panels — plywood or OSB — fastened over framing to make the wall or roof act as one surface rather than a set of separate sticks.

Every panel edge has to land on framing or on blocking. An unsupported butt joint in a roof is a soft spot underfoot and a line the roofing telegraphs.

See also on-center, blocking, layout

Board foot

A lumber volume unit: nominal thickness × nominal width in inches × length in feet, divided by 12.

Quoted on the nominal size, which is the fiction the trade prices by — a "2x4" is actually 1 1/2" by 3 1/2", but it is sold as a 2x4.

See also nominal size

Nominal size

The name a piece of lumber is sold under, not its measurement. A "2x4" is 1 1/2" by 3 1/2" once it has been dried and planed.

The difference is not a rounding error to correct — it is what the material actually is, and every layout number comes off the real dimension.

See also board foot

Rip

A cut down the length of a board, with the grain, making it narrower. Cutting across the board to length is a crosscut instead.

Most framing is used at the width it is bought. A frieze block is not: the gap it fills is whatever the rafter depth and the birdsmouth leave, which is never a stock width, so it gets ripped to fit.

See also bevel, frieze block, nominal size

Bevel

A cut made with the saw tilted, so the cut face is not square to the board. A cut made with the blade square but the board turned is a miter.

The top of a frieze block is beveled to the roof's pitch so the sheathing lands flat on it rather than on one corner.

See also rip, pitch, plumb cut

Kerf

The width of material a saw blade turns to sawdust — a strong 1/8" for a framing blade.

It sounds like a detail until a board is cut into eight pieces and comes up an inch short.

Sources

Codes, standards bodies, and trade associations — people whose business it is to be right about this. Read the ones that govern where you are building: what a jurisdiction enforces is its own amended version of a model code, and the local building department publishes it.