By The Roofing Brief Team. Last reviewed: October 2026.
A double gable roof joins two gable sections side by side so the finished roof reads as an “M” when you look at it head on. The two ridges run parallel, and where the inner slopes meet they form one central valley that runs the length of the house. Because both inner eaves sit at the same height, that valley line is level unless it is built with fall, and a level line cannot drain: IRC R903.4 requires a roof drain at each low point unless the roof drains over its edges. The term also gets used a second way, for a facade with two front-facing gables, so the first job on any plan or quote is confirming which one you mean.
What is a double gable roof?
A double gable roof is two parallel gable roofs built next to each other and tied together at a shared central valley, giving the roofline an M profile from the gable end. Each half has its own ridge and its own pair of slopes. The design lets a wide building keep a normal pitch without a very tall ridge: a single 48 ft wide gable at 6:12 rises 12 ft from eave to ridge, while two 24 ft gables at the same pitch rise 6 ft each.
The same name is applied to a house elevation with two gables facing the street, sometimes called a twin gable or double front gable facade. That version is about the elevation, common on Craftsman, Victorian and modern farmhouse plans, and it is often framed as two cross gables, each adding two sloped valleys of about 15 ft on a 20 ft wide gable at 6:12. When someone says “double gable,” ask for a roof plan and a section drawing and count the ridges and valleys before pricing anything.
Double pitched, dual pitch and double peak: which terms mean a double gable
Not every “double” roof name means a double gable. The table sorts the terms people search for.
| Term searchers use | What it usually means | Is it a double gable? |
|---|---|---|
| Double gable, twin gable, double peak roof | Two parallel gables joined at a central valley (M profile) | Yes |
| Two gable roofs (or two pitched roofs) side by side | The same M shape, often an addition built beside an existing gable | Yes |
| Multiple gable roof, multi gable roof | Three or more parallel gables (a sawtooth of M shapes), or a house with several gabled wings | Sometimes; check the roof plan |
| Split gable roof | Used loosely, either for an M roof or for a gable broken into two offset planes | Sometimes; ask for a section |
| Double pitched, dual pitched, double sloped, dual slope roof | One roof with two angled sides meeting at a ridge, the standard gable roof | No, a single gable |
| Dual pitch gable, gable roof with two different pitches | A gable whose two sides are set at different pitches, which puts the ridge off center | No, an asymmetric single gable |
| Two pitches on each side of the ridge | A gambrel roof | No |
The “dual pitched” mix-up is common enough that UK self-build guides call it out: a dual pitched roof has two sides which are angled, not two separate gables. NRCA’s roofing glossary defines a gambrel as a roof that has two pitches on each side of a central ridge.
Double gable vs cross gable vs Dutch gable
A double gable uses parallel ridges and one central valley. A cross gable uses ridges that intersect, usually at 90 degrees, creating sloped valleys where the wings meet. A Dutch gable stacks a small gable on top of a hip. The drainage difference is the one that matters: a cross gable valley slopes from ridge to eave (about 4.24:12 on a 6:12 roof), while a double gable valley runs level unless fall is framed in. Our guide to the main types of roofs sets them beside the other common shapes.
| Roof shape | Ridge layout | Valleys | Best for |
|---|---|---|---|
| Standard gable | One ridge | None | Simple rectangular footprints, lowest cost |
| Double gable (M shape) | Two parallel ridges | One central valley, level unless built with fall | Wide spans that need to keep pitch and ridge height in check |
| Cross gable | Two or more ridges intersecting, often at 90 degrees | Sloped valleys at the wing junctions | L shaped and T shaped floor plans, attached wings |
| Dutch gable | Gable set above a hip | Hip lines, no interior valley by default | Extra attic light and volume with hip style wind behavior |
The practical split: if the two ridges run the same direction, it is a double gable. If they cross, it is a cross gable roof, whose several short valleys each drain downhill at about 71 percent of the roof pitch (4.24:12 on a 6:12 roof).
The central valley: the part that decides whether it leaks
The central valley collects the full runoff of both inner roof planes, and on an M roof it runs the full length of the building. Asphalt shingles are only permitted on slopes of 2:12 or more (IRC R905.2.2), so the bottom of a level valley has to be a sheet-metal or membrane channel, and low-slope membranes need at least 1/4 inch of fall per foot (R905.9.1 built-up, R905.11.1 modified bitumen, R905.12.1 EPDM, R905.13.1 TPO and PVC).
Two ways to build it:
- Open metal valley with framed fall. Where the valley is framed to slope toward the gable ends, a metal valley at least 24 inches wide (IRC R905.2.8.2) runs under the shingles on both sides, with the roofing cut back off the center. Galvanized steel has to be at least 0.0179 in (26 gauge, G90) and aluminum at least 0.024 in per Table R905.2.8.2.
- Valley gutter (internal box gutter). On wide or long spans, the center becomes a lined internal gutter with its own outlets and downspouts, like a roof valley flashing detail scaled up. If the gutter is boxed in so water can be trapped, IRC R903.4.1 calls for overflow drains with the inlet 2 inches above the low point or scuppers three times the drain size and at least 4 inches tall.
Worked example: how much fall does the valley need?
| Valley length | Drains to | Drop at 1/4 in per ft | Drop at 1/2 in per ft |
|---|---|---|---|
| 30 ft | One end | 7.5 in | 15 in |
| 30 ft | Both ends from a center high point | 3.75 in each way | 7.5 in each way |
| 40 ft | One end | 10 in | 20 in |
| 40 ft | Both ends from a center high point | 5 in each way | 10 in each way |
| 60 ft | Both ends from a center high point | 7.5 in each way | 15 in each way |
The 1/4 inch per foot column is the IRC minimum design slope for membrane roofs (R905.9.1 to R905.13.1); the 1/2 inch column is a common upsizing for a channel that also carries debris. Drop is built with tapered blocking or a cricket under the valley lining, so draining both ways from a center high point halves the build-up height.
In snow country the valley also collects sliding snow and ice from both slopes. Where your jurisdiction shows an ice-damming history in its IRC Table R301.2 entries, the ice barrier rule (R905.1.2) applies to the eaves, and running self-adhering ASTM D1970 membrane the full width of the valley is the closed-valley lining the code already permits (R905.2.8.2).
How to join two parallel gable roofs
Joining two parallel gable roofs turns the two facing eaves into one central valley. The inner slopes of both roofs must bear on a supported line, either a bearing wall or a beam sized by the designer, with at least 1-1/2 inches of rafter bearing on wood (IRC R802.6). Because the ridges are parallel, that valley runs level, so it needs built-in fall to outlets at the gable ends.
This is the usual job when an addition goes up beside an existing gable house. The sequence:
- Confirm the support line. The valley carries roof load plus drifted snow from both roofs, so have the framing designed for it. Rafter spans for each half still come from IRC Tables R802.4.1(1) to (8), measured on the horizontal projection; beyond a 70 psf ground snow load the tables stop and the design is engineered.
- Plan the fall. Pick one-way or two-way drainage and size the drop from the worked example: a 40 ft valley falling both ways at 1/4 inch per foot needs 5 inches of build-up at the center.
- Strip the joined edge. Remove the gutter, drip edge and fascia trim on the side of the existing roof that becomes the valley, and cut the shingles back far enough for the new lining: a 36 in closed-valley ply (IRC R905.2.8.2) needs 18 in of clear deck each side of the centerline.
- Waterproof, then line. Run self-adhering ASTM D1970 membrane the full length of the valley, then install the metal valley or lined box gutter, with outlets at each low point (R903.4) and overflow where water can be trapped (R903.4.1).
- Tie the roofing in. Lap shingles or panels from both roofs onto the lining, keep nails out of the drainage path (CertainTeed’s Landmark instructions keep nails at least 6 in from a valley centerline), and match material and color so the joined roof reads as one.
If the two roofs have different pitches or ridge heights, the valley shifts off center; draw the section so it lands over the support.
Is a double gable right for your house?
| If your project has | Then | Rule behind it |
|---|---|---|
| A footprint deep enough that one gable’s ridge would exceed your height limit | Two parallel gables (M roof) keep the pitch with half the rise | Rise = half-span x pitch / 12 |
| A valley you cannot frame with fall | Lined box gutter with outlets and overflow | IRC R903.4 and R903.4.1 |
| Membrane in the valley bottom | Build at least 1/4 in per ft of fall | IRC R905.9.1 to R905.13.1 |
| Ground snow load over 70 psf | Engineered framing and a valley drift check | IRC rafter tables stop at 70 psf |
| Hurricane exposure and a hip-shape insurance credit in Florida | Consider hipped ends; gable ends count against the 10% rule | OIR-B1-1802 (Rev. 04/26), item 7 |
| Only a two-gable look on the front elevation | Twin front gables on a single roof avoid the long central valley | Fewer valleys, no level drainage line |
Pros and cons of a double gable roof
A double gable buys volume and daylight at the cost of a central valley that needs fall and cleaning.
Pros
- Keeps a normal pitch across a wide footprint: two 24 ft gables at 6:12 rise 6 ft each instead of 12 ft for one 48 ft gable.
- Four gable ends allow large windows and gable vents toward the IRC R806.2 minimum of 1/150 net free vent area (1/300 with conditions).
- Outer slopes at 4:12 or steeper take shingles over a single underlayment layer (IRC R905.2.2 requires double underlayment only from 2:12 up to 4:12).
- The twin-gable elevation suits Craftsman, Victorian and modern farmhouse plans that already use paired front gables.
Cons
- The central valley is level unless framed with fall, and needs outlets at each low point (IRC R903.4).
- Four gable ends to brace: the DOE Building America Solution Center advises bracing gable end walls taller than 48 inches in high-wind areas.
- More rakes, ridges and valley work mean more drip edge (fastened at 12 in on center per R905.2.8.5), ridge cap and flashing than a plain gable of the same size.
- Debris and snow collect in the valley; an outlet blocked by leaves backs water up toward the lining laps.
What a double gable roof costs
The covering prices at the same per-square-foot rates as any pitched roof (table below).
No published source we found measures an M roof’s premium over a single gable, so price the valley line separately.
| Roofing material | Installed cost per sq ft (2026) | Notes for a double gable |
|---|---|---|
| Architectural asphalt shingles | $5 to $8 | Shingles stop at the valley lining; the level center needs metal or membrane |
| Standing seam metal | $10 to $18 | Valley pans and closures add trim labor at the center; IRC R905.10.2 allows standing seam down to 1/4:12 |
| Concrete tile | $7 to $19 | Valley battens and closures raise labor on the M junction |
| Clay tile | $11 to $25 | Same valley detailing as concrete tile |
Rates are from our 2026 Roofing Cost Report and cover the roof surface only. On the M shaped version, budget separately for the valley system: a lined internal valley gutter with outlets and downspouts costs more than an open metal valley and is the safer specification on long or low slope spans. Ask for an itemized quote that names the valley detail, its length in feet and its fall, because that line is where double gable bids differ most.
When a double gable roof makes sense
A double gable makes sense on a wide or deep footprint where a single ridge would sit too high, and on elevations where twin gables carry the intended style. It is a weaker fit in high-wind coastal zones, where a hip roof has no gable ends to brace and, in Florida, hip geometry can qualify on form OIR-B1-1802 when gable features stay at or under 10 percent of the roof perimeter.
Design the valley with extra care if the building sits where the ground snow load is 50 psf or more, since both slopes dump into one channel and the IRC rafter tables at that load already cut a 2×8 Douglas fir-larch #2 rafter at 16 inches on center to 12 ft 6 in of span (Table R802.4.1(6), ceiling attached). Review the layout against standard gable roof framing before committing. For the wider family of gable variants, see the main gable roof guide and the rest of our roofing basics.
Frequently asked questions
What is a double gable roof?
A double gable roof is two parallel gable roofs built side by side and joined at a central valley, forming an M shape when viewed from the gable end. Two 24 ft gables at 6:12 rise 6 ft each, half the rise of one 48 ft gable. The name is also used for a facade with two front-facing gables, so confirm which meaning applies before you plan or price the roof.
Is a double gable roof the same as a cross gable roof?
No. A double gable has two ridges running in the same direction with one central valley that is level unless framed with fall. A cross gable has ridges that intersect, usually at 90 degrees, creating sloped valleys where the wings meet, about 4.24:12 on a 6:12 roof.
Does the valley on a double gable roof leak?
It can, because the valley collects the runoff of both inner planes and runs level unless fall is built in. Frame at least 1/4 inch per foot of fall (the IRC minimum for membrane roofs), line it with ASTM D1970 membrane under 24 inch metal or a lined box gutter, and provide outlets at each low point (IRC R903.4) and overflow where water can be trapped (R903.4.1).
Does a double gable roof cost more than a standard gable?
Usually yes. The covering prices at the same rate, $5 to $8 per square foot for architectural asphalt in our 2026 Roofing Cost Report, but the extra ridge, extra rakes and the central valley system add quantity and labor. We have not found a published percentage premium, so ask for an itemized valley line with its length and fall.
How do you join two parallel gable roofs?
Support both inner eaves on a bearing wall or designed beam with at least 1-1/2 inches of rafter bearing (IRC R802.6), frame fall into the valley (a 40 ft valley draining both ways at 1/4 inch per foot needs 5 inches of build-up at the center), strip the old gutter and fascia, then lay ASTM D1970 membrane and the metal valley or box gutter before tying in the roofing.
Is a double gable roof good in high wind or heavy snow?
Gable ends are the wind weak point, so in high-wind areas DOE Building America guidance is to brace gable end walls taller than 48 inches. In heavy snow the central valley collects load from both slopes, and above a 70 psf ground snow load the IRC rafter tables no longer apply, so the framing and valley need an engineered design.