Parts of a Roof
Tap any part of the roof to see its name, what it does and how it usually fails. Then peel the layers off, from shingles down to rafters.
The outside: what you can see from the street
Every roof is built from the same few lines and edges. The names tell a roofer exactly where the problem is, so they are worth knowing before you get a quote.
Tap or click a part, or use the buttons below.
The layers: what is under the shingles
This is a slice through the bottom edge of the roof, where it hangs past the wall. A shingle roof is a stack of layers, and each one backs up the one above it. Drag the slider to take them off one at a time.
All 36 parts of a roof, by where they sit
Grouped by job, not alphabet, because that is how roofers think about them: the frame holds it up, the layers keep water out, the edges send water away, the vents let the attic breathe, and the flashing seals every hole.
Structure
The frame that holds the roof up, and the attic under it.
Rafters and trusses
The sloped framing that holds the roof up. Rafters are cut on site; trusses are pre-built triangles made in a factory.
Watch for: Sagging between rafters can mean water-damaged decking or an overloaded frame. Ask for an attic check.
Ceiling joist
The level framing that forms the attic floor and the ceiling below. It also ties the bottoms of the rafters together.
Watch for: Water stains on joists in the attic show where a leak is, often far from where it drips into the room.
Wall and top plate
The outside wall of the house. The top plate is the board along its top that the rafters sit on.
Watch for: Ice and water shield is measured from here: code asks for it to reach at least 24 inches inside this wall line.
Attic insulation
The blanket on the attic floor that keeps heat in the house and out of the attic.
Watch for: Too little insulation melts snow on the roof, which refreezes at the eaves as an ice dam.
Collar tie
A level board joining pairs of rafters high up in the attic, keeping them from spreading apart.
Watch for: Do not cut collar ties to make attic space without an engineer.
Ridge board
The board at the peak that the tops of the rafters are nailed against.
Watch for: A sagging ridge line seen from the street is worth an attic inspection.
Attic
The space between the ceiling and the roof. It has to breathe to keep the roof dry.
Watch for: Frost, mold or a musty smell in the attic means the ventilation is not working.
Deck and layers
The stack that keeps water out, from the boards up to the shingles.
Shingles
The outer layer of the roof, also called the roof covering. In most US homes this is asphalt shingles; other coverings include metal, tile and slate.
Watch for: Wear shows as lost granules, curling, cracking or bare spots, usually late in a roof's life.
Decking (sheathing)
The plywood or OSB boards nailed over the rafters. Everything else is fastened to it.
Watch for: Soft or spongy spots mean rotten decking. Quotes often price replacement per sheet, so ask how many sheets are included.
Ice and water shield
A sticky, self-sealing rubbery membrane laid along the eaves and in valleys. It seals around nails.
Watch for: Where ice dams are common, code (IRC R905.1.2) requires it from the edge to at least 24 inches inside the outside wall.
Underlayment
A sheet of felt or synthetic fabric over the whole deck, under the shingles. It is the backup layer when water gets past the shingles.
Watch for: Synthetic underlayment is now the norm on most re-roofs. Ask which one your quote includes.
Starter strip
A row of shingles laid along the eaves and rakes before the first full course, so the first course is sealed down and its gaps are covered.
Watch for: Without it, the first row of shingles blows off first and water gets in through the gaps.
Ridge cap
Folded shingles that cover the ridge and hips.
Watch for: Ridge caps cut from regular 3-tab shingles crack faster than purpose-made cap shingles.
Shapes and lines
The names for the roof's peaks, corners and faces.
Ridge
The level peak where two roof slopes meet at the top.
Watch for: Covered with ridge cap shingles. High winds lift ridge caps first, so check them after a storm.
Hip
The sloped outside corner where two roof slopes meet, running from the ridge down to a corner of the house.
Watch for: Capped like the ridge. Loose hip caps are a common storm repair.
Valley
The inside corner where two slopes meet and pour water into one channel.
Watch for: Carries more water than any other part of the roof, so it is one of the first places to leak. Usually lined with ice and water shield or metal.
Gable
The triangle of wall under the two slopes at the end of a roof.
Watch for: The gable wall itself rarely leaks, but its edges (the rakes) take the full force of wind.
Dormer
A small roofed structure that sticks out of the main roof, usually with a window.
Watch for: Every dormer adds walls, valleys and flashing, which means more places to leak.
Pitch (slope)
How steep the roof is, given as rise over 12 inches of run. A 6/12 roof rises 6 inches every foot.
Watch for: Steep roofs cost more to work on. Very low slopes need different materials than shingles.
Edges and trim
Where the roof ends and water leaves it.
Rake
The sloped edge of a roof along the side of a gable, running from the eave up to the ridge.
Watch for: Wind gets under rake edges. Shingles here need proper nailing and a drip edge.
Eave
The level bottom edge of a roof slope that hangs past the wall. Water runs off here.
Watch for: In cold places, ice dams form at the eaves and push water back under the shingles.
Fascia
The upright board along the roof edge. The gutter is fastened to it.
Watch for: Rots when gutters overflow or there is no drip edge. Soft fascia means water has been getting behind the gutter.
Drip edge
An L-shaped metal strip along the eaves and rakes that throws water clear of the fascia.
Watch for: Required on shingle roofs in most of the US since the 2012 building code. Missing drip edge leads to rotten decking at the edges.
Gutter
The channel hung on the fascia that catches water running off the eave.
Watch for: Clogged or sagging gutters overflow behind the fascia and into the soffit and walls.
Downspout
The pipe that carries water from the gutter down to the ground and away from the foundation.
Watch for: A downspout that dumps water next to the house can cause basement and foundation problems.
Soffit
The flat panel under the roof overhang, between the wall and the fascia. Vented soffit is how most attics breathe in.
Watch for: Peeling paint or stains on the soffit point to a leak above it.
Ventilation
How the attic breathes: air in low, air out high.
Ridge vent
A low vent running along the ridge that lets hot, damp attic air out at the highest point.
Watch for: Works only with intake vents low down at the soffits. A ridge vent with blocked soffits does almost nothing.
Baffle (vent chute)
A channel fixed between rafters that keeps insulation from blocking the air coming in from the soffit.
Watch for: Missing baffles mean the soffit vents are buried in insulation, which traps heat and moisture and helps ice dams form.
Soffit vent (intake)
Holes or slots in the soffit that let cool outside air into the bottom of the attic.
Watch for: Code asks for ventilation balanced between low intake and high exhaust. Blocked intake is the most common ventilation problem.
Flashing and openings
Metal and rubber seals at every place the roof is interrupted.
Chimney flashing
Metal pieces that seal the joint between the chimney and the roof: step flashing along the sides, counter flashing set into the brick above it.
Watch for: The single most common leak source on older roofs. Caulk alone is a temporary fix, not flashing.
Pipe boot
A rubber collar with a metal or plastic base that seals around a plumbing vent pipe.
Watch for: The rubber cracks in the sun, often years before the shingles wear out. A cheap part that causes a lot of ceiling stains.
Skylight
A window set into the roof, sealed with its own flashing kit.
Watch for: Leaks usually come from the flashing around the frame, not from the glass.
Step flashing
Small L-shaped metal pieces woven in with each row of shingles where a roof slope meets a wall.
Watch for: Often reused or skipped on cheap re-roofs. Ask whether the quote includes new step flashing.
Counter flashing
Metal set into a wall or the mortar of a chimney that laps down over the step flashing.
Watch for: If it is only glued to the brick face, it will pull loose.
Kickout flashing
A small diverter at the bottom of a roof-to-wall joint that kicks water into the gutter instead of down the wall.
Watch for: A missing kickout is a classic cause of hidden rot in the wall below.
Cricket (saddle)
A small peaked roof built behind a chimney so water flows around it instead of pooling.
Watch for: The building code requires one behind chimneys wider than 30 inches.
Rake vs eave, and fascia vs soffit
These are the four words people mix up most.
Which parts of a roof fail first
Most leaks do not start in the open field of shingles. They start where the roof is interrupted. If your roof leaks, these are the places a good roofer checks first:
- Flashing at chimneys, walls and dormers: sealant dries out and metal lifts or rusts.
- Pipe boots: the rubber collar around plumbing vents cracks in the sun, often well before the shingles wear out.
- Valleys: two slopes pour all their water into one channel, so any gap shows up here.
- Skylights: the flashing kit around them, more often than the glass.
- Eaves in cold climates: ice dams push water back under the shingles where there is no ice and water shield.
- The shingles themselves: granule loss, curling and cracking, usually late in the roof's life.
Why this matters to your wallet: the first five can often be repaired. If a roofer quotes a full replacement for a leak at one of these spots, ask why a repair will not do, and get a second quote. Our roof cost calculator gives you a fair range before anyone climbs a ladder.
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Questions people ask
What are the main parts of a roof?
From the bottom up: the frame (rafters or trusses), the decking, ice and water shield at the edges, underlayment, a starter strip, the shingles and the ridge cap. Around the edges are the drip edge, fascia, soffit and gutters. Flashing seals every place the roof meets a wall, chimney, valley or pipe.
What is the edge of a roof called?
The level bottom edge is the eave. The sloped edge on the end of a gable is the rake. The board that covers both is the fascia, and the metal strip bent over it is the drip edge.
What is under the shingles on a roof?
Underlayment, then (along the eaves and in valleys) a self-sealing ice and water shield, then the decking, which is nailed to the rafters or trusses.
Does a roof need a drip edge?
For asphalt shingles, yes in most of the US. The International Residential Code (R905.2.8.5) has required a drip edge at eaves and rakes of shingle roofs since the 2012 edition.
How much attic ventilation does a roof need?
The International Residential Code (R806.2) asks for 1 square foot of net vent area for every 150 square feet of attic floor, or 1 per 300 when the vents are balanced between low intake and high exhaust. Your local code can differ, so ask the roofer to show the math.
Sources: International Code Council, 2021 International Residential Code, chapter 8 (R806 roof ventilation) and chapter 9 (R905.1.2 ice barrier, R905.2.8.5 drip edge). Part names follow common US residential roofing usage. Your local building department has the final word on code in your area.