Gable
Very commonTwo planes meeting at a central ridge, leaving a triangular wall at each end.
4:12 to 9:12 typical
What goes wrong, and what it costs
Roof types, shapes and slopes
A field guide to every residential roof form we work on in the Kansas City metro, what the pitch means for your material choice, and how to name the part that is giving you trouble.
Two houses on the same street with the same square footage can be completely different roofs. What separates them is shape and pitch: how many planes the roof has, how those planes meet, and how steeply they run. Those two things decide what materials are allowed, how long the job takes, where it will leak first, and what it costs.
This page is the reference we wish more homeowners had before calling for a quote. Start with the anatomy, because being able to name the part that is wet turns a confusing phone call into a dispatch.
Know what you are looking at
- 1Ridge and ridge ventThe horizontal peak. The vent hides under the cap shingles and is the exhaust half of your attic ventilation. Cap shingles blow off here first, because the ridge takes the most wind uplift.
- 2ValleyThe internal angle where two roof planes drain toward each other. It carries more water per foot than anywhere else on the roof, which is why it is one of the most common places a leak starts.
- 3Chimney flashing and cricketA chimney wider than 30 inches across the slope needs a cricket, a small peaked saddle on the uphill side, so water splits around it instead of ponding. Tar smeared on brick is a repair that fails.
- 4Roof-to-wall step flashingWhere a roof plane runs up alongside a wall, water is held back by many small interwoven L-shaped pieces, one per shingle course. Never a single strip and never caulk.
- 5Pipe bootThe rubber collar sealing each plumbing vent. The collar dries out and cracks in about 10 to 15 years, well before the shingles do, which makes this the most common small leak on a roof and usually a repair rather than a replacement.
- 6Eave and gutterThe level lower edge, where water leaves the roof. This is the ice dam zone in a Kansas winter. Water pouring off the front of the house in a storm is usually a clogged gutter, not a roof leak.
- 7RakeThe sloped edge running up the gable end. Easy to confuse with the eave, so remember it this way: the eave is level, the rake is sloped. They fail differently and are flashed differently.
- 8Soffit and fasciaThe underside of the overhang and the board the gutter hangs on. The soffit is also the intake half of your ventilation, and attic insulation blocking it from the inside is common and invisible from the ground.
Slope decides your options
Pitch is rise over twelve inches of run. It is not a style choice, it is a constraint. Drag the slope below and watch what you are allowed to put on it.
0:126:1212:12
6:12about 27° from horizontal
ConventionalEvery common material is in play
Shingles, metal, tile or shake, each still subject to its own manufacturer minimum. Walkable for a roofer, standard labor rate, and where most Kansas City homes sit. This range is trade convention rather than a code band.
Trade convention, not code
At this slope
- Asphalt shingles
- Standing seam metal
- TPO / EPDM membrane
- Modified bitumen
- Wood shake
- Tile
Membrane drops out at 4:12 and above because nobody specifies it there, not because the code forbids it. Shake and tile carry manufacturer minimums of their own, so treat these as a starting point rather than an approval.
The part almost nobody accounts for
A valley is always shallower than the two roof planes that create it. The NRCA puts a number on it: where two 4:12 planes meet, the valley itself runs at only about 3:12.
So a roof specified at 4:12 is quietly draining its most water-loaded line at 3:12, below the 4:12 the NRCA recommends for shingles and only one step above the 2:12 code floor. It is the reason cross-gabled and cross-hipped roofs leak in the valleys rather than in the open field, and the reason a complex roof should be designed steeper than the minimum rather than at it.
| Slope band | Pitch | What it takes | Why |
|---|---|---|---|
| Flat | Under 2:12 | Membrane only: TPO, EPDM or modified bitumen | Asphalt shingles are not permitted here. IRC R905.2.2 sets 2:12 as the hard floor for shingles. |
| Low slope | 2:12 to under 4:12 | Shingles permitted, with a double layer of underlayment | The double underlayment is a code requirement at this pitch, not an upgrade. Metal and membrane also work well. |
| Conventional | 4:12 to 9:12 | Anything: shingles, metal, tile, shake | Walkable for a roofer, standard labor rate, and where most Kansas City homes sit. |
| Steep slope | Over 9:12 | Anything, but installed with fall protection | Harnesses, roof jacks and slower work. Expect a meaningful labor premium over an identical area at 6:12. |
What shape is my roof?
Answer what you can see from outside. Skip anything you are unsure of.
Every shape we work on
13 forms. The rectangular-plan shapes are drawn on one shared footprint so their silhouettes compare directly; the hexagonal, domed and round-tower forms do not sit on a rectangle, and the cross gable is drawn from above because its ridges are what define it. Find yours, then open its page for what tends to go wrong and what a replacement involves.
Hip
Very commonAll four sides slope down to the walls, meeting at a ridge shorter than the building.
4:12 to 8:12 typical
What goes wrong, and what it costsCross gable and combination
Very commonTwo or more roof sections meeting at right angles, producing valleys where the planes intersect.
Varies by section
What goes wrong, and what it costsPyramid hip
OccasionalFour triangular planes rising to a single point, with no ridge line at all.
4:12 to 8:12 typical
What goes wrong, and what it costsGambrel
OccasionalThe barn profile: a steep lower slope and a shallow upper slope on each side.
Lower slope 20:12 or steeper, upper often 4:12 or less
What goes wrong, and what it costsMansard
RareA near-vertical lower slope on all four sides with a nearly flat deck on top.
Lower slope up to 70 degrees, upper deck often under 2:12
What goes wrong, and what it costsShed and skillion
OccasionalA single plane sloping in one direction, with no ridge at all.
3:12 to 15:12, wide range
What goes wrong, and what it costsFlat and low slope
OccasionalA single plane with just enough fall to drain, typically a quarter inch per foot.
Under 2:12
What goes wrong, and what it costsSaltbox
RareAn asymmetric gable, with the ridge set off centre so one slope is much longer than the other.
6:12 to 12:12 typical
What goes wrong, and what it costsButterfly
RareTwo planes sloping inward to a central valley, shaped like a pair of open wings.
Low, usually under 4:12
What goes wrong, and what it costsHexagonal and polygonal
RareSix or more triangular planes meeting at a central peak, with a hip running down to every corner.
Often steep, 8:12 and up
What goes wrong, and what it costsGeodesic dome
RareA sphere approximated by a lattice of triangles, with no flat plane anywhere on it.
Continuously curved, from near vertical to near flat
What goes wrong, and what it costsConical turret
RareA cone over a round tower, usually as an accent rather than a whole roof.
Steep, often 12:12 and up
What goes wrong, and what it costsThe roofs other crews decline
Hexagonal, turret and geodesic dome
People find us by phone for these, usually after being told no a few times. It is worth being honest about why: they are harder, and the difficulty is geometric rather than a matter of effort.
A shingle is a flat rectangle. It lies down happily on a flat plane. On a hexagonal turret every course has to be cut to a taper, and six hip lines converge at a point that has to be capped without leaving a hole. On a geodesic dome there is no flat plane anywhere, the pitch changes continuously from near vertical at the base to near flat at the crown, and the lattice creates hundreds of seams.
So the answer is often not shingles at all. Sometimes it is a membrane, sometimes standing seam or a panel system, sometimes a hybrid where the steep lower band and the shallow crown are treated as two different roofs. We would rather scope that properly than quote something that will fail in five years.
What you are seeing, and what it usually means
Most of what homeowners describe as a roof leak turns out to start at a transition rather than out in the open field of shingles. This is roughly how we triage a call.
- “Water pouring off the front of the house in a storm”
- Usually a clogged gutter, not a roof leak
- “Small ceiling stain that grows when it rains hard”
- A pipe boot, or a valley above it
- “Stain where an upstairs wall meets the ceiling”
- Step flashing on a roof-to-wall run
- “Wet spot near the fireplace”
- Chimney flashing, or a missing cricket
- “Icicles, and water dripping in behind the gutter”
- An ice dam at the eave
- “Drips around a skylight”
- Skylight flashing, or condensation from poor attic ventilation
- “The wood under the roof edge is going soft”
- Soffit and fascia, caused by a gutter or ice dam above
- “Shingles in the yard after a storm”
- Field shingles or ridge caps, and a question about the starter course
None of this replaces getting on the roof. It does mean that when you call, we can bring the right thing on the truck.
Common questions
What is the most common roof type on houses?
The gable, two planes meeting at a ridge with a triangular wall at each end. It is the cheapest shape to frame, sheds water and snow efficiently, and gives generous attic volume. Across Johnson County the hip roof is close behind, and most larger homes are a combination of the two.
What is the minimum roof pitch for asphalt shingles?
Two in twelve. Under IRC R905.2.2 asphalt shingles may only be used on slopes of 2:12 and greater, and between 2:12 and just under 4:12 a double layer of underlayment is required. Below 2:12 you need a membrane such as TPO, EPDM or modified bitumen, not shingles.
Does roof shape affect how much a replacement costs?
More than square footage does, past a point. Valleys, hips, dormers and changes of pitch all add cut shingles, flashing and labor. Two houses with the same roof area can differ by thousands if one is a simple gable and the other is a cross-gabled roof with three dormers.
Do you work on hexagonal roofs, turrets and geodesic domes?
Yes, and we get calls for them specifically because many crews will not quote them. They are genuinely harder: a dome has no flat plane anywhere on it, so shingles cannot lie flat and the detailing is unlike any other roof. We will scope one honestly and tell you if a different covering makes more sense than shingles.
Which roof shape holds up best in Kansas wind?
A hip roof, but with a caveat most contractors leave out. Wind tunnel research found a hip roof cut worst-case peak suction by up to half compared with a gable, and that finding is where the whole hip-is-better claim comes from. It was measured on 4:12 roofs. Later work testing hip roofs across pitches found the advantage shrinks as the roof gets steeper and is close to gone by roughly 7:12, which is inside the normal range here. Shape also matters less than installation: a properly started and fastened gable roof outperforms a hip roof whose rake edges and ridge caps were cut from field shingles.
How do I know what pitch my roof is?
Pitch is the rise in inches over twelve inches of horizontal run. From the ground you can estimate it by comparison, but the reliable way is from inside the attic with a level and a tape measure, or by having someone measure it during an inspection. Pitch decides what materials are permitted, so it is worth knowing accurately.
Where these numbers come from
Every code figure on this page is checkable. If a claim is a rule of thumb rather than a code requirement, we have said so in the text rather than dressing it up as a standard.
Which code applies to you. Kansas City, Missouri and the State of Kansas have both adopted the 2018 International Residential Code, but Johnson County cities, including Overland Park, Olathe, Lenexa and Leawood, adopt and amend independently and on their own schedules. Treat the sections below as the model code, and confirm the detail with your jurisdiction before making a decision that hinges on it. We pull the permit on every job, so we do that check anyway.
Building code
- IRC R905.2.2, Slope
Asphalt shingles are permitted only on slopes of 2:12 and greater. From 2:12 up to 4:12, double underlayment is required.
- IRC R903.2.2, Crickets and saddles
A cricket or saddle is required on the ridge side of any chimney or penetration more than 30 inches wide, measured perpendicular to the slope.
- IRC R1003.20 and Table R1003.20
The masonry chimney version of the cricket rule, including the required cricket height for a given chimney width and roof slope. Adds an exception where the chimney intersects the ridge.
- IRC R905.2.8.3, Sidewall flashing
Base flashing against a vertical sidewall shall be continuous or step flashing, not less than 4 inches high and 4 inches wide.
- IRC R903.2.1, Flashing locations
Requires a flashing that diverts water away from where the eave of a sloped roof meets a vertical sidewall. This is the kick-out flashing requirement, although the model code never uses that word.
- IRC R905.2.8.5, Drip edge
Drip edge is required at both eaves and rake edges. The lapping order reverses between the two.
- IRC R905.1.2, Ice barriers
Where a history of ice forming at the eaves exists, an ice barrier must extend from the roof edge to a point at least 24 inches inside the exterior wall line.
- IRC R806.2, Minimum vent area
Attic ventilation of 1/150 of the vented area, reducible to 1/300 where the exhaust sits high and the balance is provided at the eaves.
Industry and manufacturer
- NRCA, In the valley
Open, closed-cut and woven valley construction, and why the NRCA does not recommend woven valleys.
- NRCA, Roof slope guidelines
The valley-slope rule quoted above, verbatim: where 4:12 planes intersect, the valley runs at about 3:12. Also the NRCA minimums, which are steeper than code for every steep-slope material.
- NPS Preservation Brief 29, Historic Slate Roofs
Slate headlap by slope, graduated coursing on turrets, round valleys, and the installation rates behind why complex roofs cost what they do.
- NRCA, Know your steep-slope roof decks
Minimum deck thickness for a given framing spacing, and the case for plywood over OSB.
- IIBEC, Common problems with residential counterflashing
Why surface-mounted counter flashing fails and what a correct reglet detail looks like.
- Building Science Corporation, Understanding attic ventilation
Balanced intake and exhaust, and the case against powered attic ventilators.
- Kansas Attorney General, Roofing Registration
Paid roofing contractors generally need a Kansas registration certificate unless an exemption applies. Use the Kansas Attorney General's registration resources to verify the current registration.
One claim you will not find here: the figure that a fixed percentage of roof leaks originate at flashings. It is repeated across the industry and attributed to the NRCA, but it does not appear in any NRCA publication we could locate, so we have left it out and said only what the NRCA does state, that the joint between a horizontal deck and a vertical surface is the most vulnerable part of any roof.
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