By The Roofing Brief Team. Last reviewed: October 2026.
A cross gable roof (also called a cross gabled roof, crossed gable roof, or intersecting gable roof) is two or more gable roof sections that intersect at right angles, so the ridges run perpendicular to each other over an L-shaped, T-shaped, or cruciform footprint. Each section keeps the two sloping planes and triangular end wall of a standard gable, but where the sections cross, the planes form valleys. Under the 2021 IRC, a stick-framed valley needs a valley rafter at least 2 inches nominal and as deep as the rafter cut end (R802.4.3) and a valley lining at least 24 inches wide in metal or 36 inches wide in a closed-valley ply (R905.2.8.2).
Builders reach for a cross gable when a house is not a simple rectangle: a wing off the main body, an attached garage, a projecting entry, or a dormer that reads as its own gabled volume. A 24 ft wide wing at 6:12 adds two valleys of about 18 ft each where it meets the main roof (worked out in the framing section below), and every foot of that valley has to be lined and flashed correctly or it leaks.
What is a cross gable roof?
A cross gable roof is a roof formed by two or more intersecting gable sections whose ridges meet at right angles, creating internal valleys at each junction. It is the standard roof for L-shaped and T-shaped houses, where one gabled wing crosses the main gabled body. Unlike a single gable, which has one ridge and two slopes, a cross gable has multiple ridges, multiple gable ends, and a valley wherever two roof planes turn an inside corner. Each of those is a change in roof direction, one of the places IRC R903.2.1 requires flashing.
The name describes the geometry, not a different building method. Each arm is framed like any gable: paired rafters or trusses running from an exterior wall up to a ridge board at least 1 inch nominal and as deep as the rafter cut end (IRC R802.3). The complexity lives at the intersections, where the two planes die into each other and a valley rafter carries the jack rafters down to the corner.
Cross gable roof design and shapes
Cross gable roofs are named by the shape the ridges make in plan: the L, the T, and the cruciform (a full cross).
| Configuration | Footprint | Number of valleys | Typical use |
|---|---|---|---|
| L-shape | Main body with one perpendicular wing | 2 where the wing’s two planes die into the main roof (1 valley plus 1 hip if the ridges meet at a corner) | House with an attached garage or side wing |
| T-shape | Wing meeting the main ridge at the middle | 2 | Projecting entry, central dormer wing, rear addition |
| Cruciform (full cross) | Four arms meeting at a central point | 4 | Symmetrical designs, some churches and larger custom homes |
When the two crossing sections share the same pitch, each valley runs at exactly 45 degrees in plan and the eave lines align. Crossing sections of unequal pitch or unequal ridge height produce an irregular valley that is harder to frame and flash, and a wing ridge set lower than the main ridge dies into the main roof plane rather than meeting its ridge.
Cross gable roof framing: valley rafters, jacks and trusses
In stick framing, a valley rafter runs from the inside corner of the walls up to the ridge, and shortened jack rafters run from the ridges down onto it. IRC R802.4.3 sets the valley rafter at not less than 2 inches nominal thickness and not less in depth than the cut end of the rafters, and requires it to be braced at the ridge to a bearing partition or designed for the point load. Where the pitch is below 3:12, R802.4.4 requires ridges, hips and valleys to be designed as beams.
Trussed cross gables are usually built with a set of valley trusses that sit on top of the main roof’s trusses or sheathing. Their layout and bearing come from the truss design drawings, which IRC R802.10.1 requires to be approved and delivered with the trusses, and R802.10.4 bars cutting or notching any truss member without a registered design professional’s approval. The 2021 IRC text is on the ICC chapter 8 page.
Valley length and slope: a worked framing table
With equal pitches, each valley rafter covers a horizontal run equal to the wing’s half-span times 1.414 (the 45 degree diagonal), so its true length is the half-span times the square root of (2 plus (pitch / 12) squared). On a framing square that is 16.97 in of valley run for every 12 in of common run. The table applies that to common wing widths. Use it to order valley lining and to check a bid’s valley footage.
| Wing width (span) | Valley length at 4:12 | at 6:12 | at 8:12 | at 12:12 |
|---|---|---|---|---|
| 16 ft | 11.6 ft | 12.0 ft | 12.5 ft | 13.9 ft |
| 20 ft | 14.5 ft | 15.0 ft | 15.6 ft | 17.3 ft |
| 24 ft | 17.4 ft | 18.0 ft | 18.8 ft | 20.8 ft |
| 28 ft | 20.3 ft | 21.0 ft | 21.9 ft | 24.2 ft |
Lengths are eave to ridge for one valley, assuming the wing ridge dies into the main roof and both sections share eave height. A T or L wing has two such valleys. The valley itself is shallower than the roof planes: its slope is the roof pitch divided by 1.414, so a 6:12 roof drains through a valley at about 4.24:12 and a 4:12 roof through a valley at about 2.83:12, which is why water lingers there longer than on the open plane.
Cross gable vs gable: what is the difference?
A standard gable roof has one ridge, two sloping planes and two triangular gable ends, and it carries no valleys. A cross gable has two or more of those sections crossing at right angles, which adds ridges, adds gable ends, and creates a valley at every intersection. On the Florida wind mitigation form OIR-B1-1802 (Rev. 04/26), a roof only counts as hip if non-hip features are 10 percent or less of the total roof perimeter, so gabled wings on an otherwise hipped house can move it to “other.”
| Feature | Standard gable roof | Cross gable roof |
|---|---|---|
| Ridges | One | Two or more, at right angles |
| Valleys | None | 2 per wing on an L or T, 4 on a full cross |
| Best-fit footprint | Rectangle | L, T, or cross shape |
| Relative cost | Lower | Higher: valley rafters, valley lining, more cut shingles |
| Main leak point | Penetrations and eaves | Valleys and gable-to-wall junctions |
| Framing difficulty | Common rafters or trusses only | Valley rafters per IRC R802.4.3, jack rafters, or valley truss sets |
If your house is a plain rectangle, a single gable does the job with no valleys. The cross gable earns its place when the plan is already broken into wings, because a wing roofed with its own aligned gable drains through two lined valleys, about 18 ft each on a 24 ft wing at 6:12, instead of the long, shallow crickets a single forced roof would need. Where two wings run parallel instead of crossing, the layout becomes a double gable roof, which keeps its valley between the two ridges rather than at an inside corner. For how the underlying rafters and trusses come together in either case, see our gable roof framing guide.
Which roof fits your plan?
| If your plan or site has | Choose | Rule behind it |
|---|---|---|
| A plain rectangle | Single side or front gable | No valleys to line or maintain |
| A wing narrower than the main body, same pitch | Cross gable with the wing ridge dying into the main roof | Equal pitch gives 45 degree valleys and aligned eaves |
| A design pitch below 3:12 | Engineered valley and ridge members, or a different roof form | IRC R802.4.4: supports designed as beams |
| Ice-dam history at the eaves | Open metal or closed valley over self-adhering membrane, plus eave ice barrier | IRC R905.1.2 and R905.2.8.2 |
| A hip-shape insurance credit in Florida | Hip the wings, or keep gable features under 10% of roof perimeter | OIR-B1-1802 (Rev. 04/26), item 7 |
| Tall gable ends in a high-wind zone | Brace gable walls over 48 inches tall, or use a hip or Dutch gable | DOE Building America guidance below |
Cross gable roof valleys: the key leak risk
Valleys are where two roof planes meet at an inside corner and channel the runoff of both planes down a single line that is shallower than either plane (see the slope note above). IRC R905.2.8.2 makes the valley lining a code item, installed to the shingle maker’s instructions before the shingles go on, and the maker’s instructions set the trim and nailing distances that keep water out.
| Valley method | Lining the code allows | Maker detail (example) | Source |
|---|---|---|---|
| Open metal valley | At least 24 in wide; e.g. galvanized steel 0.0179 in (26 ga, G90), aluminum 0.024 in, or 16 oz cold-rolled copper | Shingles cut back from the exposed metal on both sides | IRC R905.2.8.2 and Table R905.2.8.2 |
| Open valley, roll roofing | Two plies of mineral-surfaced roll roofing: 18 in bottom, 36 in top | Not common on new laminated-shingle roofs | IRC R905.2.8.2 item 2 |
| Closed-cut valley | One 36 in ply of smooth roll roofing (ASTM D6380), or ASTM D1970 self-adhering membrane | CertainTeed Landmark: 36 in waterproofing underlayment, shingles cut 2 in back from the centerline, no nails within 6 in of it | CertainTeed Landmark instructions |
| Woven valley | Same closed-valley lining | CertainTeed accepts woven for Landmark; GAF directs its laminated shingles, such as Timberline, to open or closed-cut valleys | GAF bulletin R-136 |
Several guides say woven valleys cannot be done with laminated shingles at all. The maker documents differ: CertainTeed’s Landmark instructions prefer closed-cut but list open and woven valleys as acceptable, while GAF’s valley bulletin keeps laminated lines such as GAF Timberline HDZ to open or closed-cut. Check the instructions for the exact shingle on your bid, because the warranty follows them. For metal profiles, laps and fastener placement, see our valley flashing detail guide.
Where a cross gable wing ties into a taller wall rather than another roof plane, that junction needs base flashing at least 4 inches high and 4 inches wide, continuous or stepped, with the vertical leg under the siding (IRC R905.2.8.3), plus a kickout where the eave meets the wall (R903.2.1). A valley also dumps its flow into one gutter corner, so size the valley and gutter transition for the runoff of two planes, not one.
Cross gable roof pros and cons
The cross gable trades more valleys and framing for a roof that follows a winged plan without one oversized ridge.
| Pros | Cons |
|---|---|
| Fits L, T, and cruciform floor plans that a single gable cannot cover cleanly | Each wing adds 2 valleys, roughly 12 to 21 ft each on 16 to 28 ft wings at 6:12 |
| Adds attic and vaulted-ceiling volume under the extra ridges | Valley rafters per IRC R802.4.3, or valley truss sets, add framing time |
| Each wing gets its own gable end for windows and gable vents | Valleys drain at about 71 percent of the plane’s pitch and collect debris |
| Each ridge can carry ridge vent toward the IRC R806.2 minimum of 1/150 net free vent area (1/300 with conditions) | More gable ends to brace in high-wind zones |
| Wings can be hipped on exposed sides to keep a Florida hip classification (10% rule) | Gabled wings over 10% of the perimeter lose the OIR-B1-1802 hip classification |
For tall gable ends, the DOE Building America Solution Center advises bracing gable end walls taller than 48 inches with horizontal braces, retrofit studs and compression blocks, and notes the IBHS FORTIFIED Home Hurricane standard calls for 7/16 in OSB or plywood on the face of the gable wall. If you want the crossed-gable look with fewer valleys, a Dutch gable or a hip-and-gable hybrid can soften the intersections while keeping the gable ends. If attic volume matters more than the crossed look, a gambrel roof uses a steeper two-slope profile under a single ridge. If exposed gable ends in a high-wind area are the bigger worry, a hip roof with slopes on all four sides removes the tall end walls altogether.
Cost and maintenance of a cross gable roof
A cross gable costs more than a simple gable of the same area because each valley adds framing, lining and cut shingles. The roof covering itself prices at the same per-foot rate: architectural asphalt runs $5 to $8 per square foot installed and standing seam metal $10 to $18 in our 2026 Roofing Cost Report. What changes is quantity and labor:
- Framing: valley rafters must be 2 inches nominal minimum and as deep as the rafter cut end (IRC R802.4.3), and every jack rafter gets a compound cut; trussed cross gables need a valley truss set on the truss drawings.
- Valley lining: each valley needs 24 in metal or a 36 in closed-valley ply its full length (R905.2.8.2); a 24 ft wing at 6:12 means about 36 ft of lining for its two valleys, before laps.
- Waste factor: roofing estimator Roofr’s waste-factor guide uses 10 to 15 percent as a general estimate and calls for more on roofs with many valleys, hips and dormers.
- Maintenance: clear valleys of leaves and grit at least once a year and after storms, and check the metal or the 2 in cut line on closed-cut valleys for exposed nails or lifted shingles.
Inspect the valleys first after any storm. On a closed-cut valley, the first sign of trouble is often a shingle edge that has lifted along the cut line or a nail head visible within 6 inches of the centerline, the zone CertainTeed’s instructions keep nail-free.
Cross gable roofs: frequently asked questions
What is a cross gable roof?
A cross gable roof is two or more gable roof sections that intersect at right angles, forming perpendicular ridges over an L-shaped, T-shaped, or cruciform house. Where they cross, the planes create valleys: two per wing on an L or T and four on a full cross, each lined per IRC R905.2.8.2.
What is the difference between a gable and a cross gable roof?
A standard gable roof has one ridge, two slopes, two triangular ends, and no valleys. A cross gable has two or more of those sections crossing at right angles, which adds ridges and gable ends and creates valleys that need valley rafters (IRC R802.4.3) and valley lining (R905.2.8.2).
Why do cross gable roofs leak at the valleys?
Valleys collect the runoff of two planes into one channel that is shallower than the roof itself: about 4.24:12 on a 6:12 roof. Leaks usually trace to lining that is too narrow (the IRC calls for 24 in metal or 36 in closed-valley lining), nails inside the 6 in zone around the centerline, or debris holding water in the valley.
Which valley type is best for a cross gable roof?
Open metal valleys at least 24 inches wide shed water and debris fastest. Closed-cut valleys over a 36 inch membrane are the most common on laminated asphalt; CertainTeed prefers them for Landmark. Woven valleys depend on the maker: CertainTeed accepts them for Landmark, while GAF directs laminated shingles such as Timberline to open or closed-cut valleys.
Is a cross gable roof more expensive than a regular gable roof?
Yes. The covering costs the same per square foot (architectural asphalt $5 to $8 installed in our 2026 Roofing Cost Report), but valley rafters, valley lining and extra cut shingles add labor and material. Roofr’s estimating guide uses a 10 to 15 percent waste factor in general and more on roofs with many valleys and hips.
What house shapes suit a cross gable roof?
Cross gable roofs suit L-shaped, T-shaped, and cruciform floor plans, where a wing, garage, or projecting entry crosses the main body of the house. On a simple rectangle a single gable has no valleys. With equal pitches on both sections, the valleys run at 45 degrees in plan and the eaves line up.