Gambrel roofs

Two different slopes on each side — steep below, shallow above — giving the classic barn silhouette and a lot of usable space upstairs.

Typical pitch: Lower slope 20:12 or steeper, upper often 4:12 or less
How often we see it: Occasional

Pitch ranges are trade convention, not code. Code sets minimum slope by material, not by roof shape.

Is this your roof?

Each side of the roof visibly changes angle partway down.
The lower slope is steep, often close to vertical; the upper slope is shallow.
From the end, the outline reads as a barn or a Dutch colonial.

In Johnson County

The shallow upper slope is the part to watch in Kansas. It sheds water slowly, holds snow longer, and is the section most likely to fall below 4:12. From 2:12 up to 4:12 the 2018 IRC requires the low-slope double underlayment application rather than a standard single layer, and below 2:12 asphalt shingles are not permitted at all. Get that upper slope measured rather than assumed, because it changes both the specification and the price.

What you can put on it

Material choice on this shape, and where code rather than preference makes the decision for you.

Asphalt shingles

Works well

Standard, but confirm the upper slope's pitch. From 2:12 up to 4:12 it needs the low-slope double underlayment application, and below 2:12 shingles are not permitted there at all.

Standing seam metal

Works well

Suits the barn idiom and handles the shallow upper slope better than shingles do.

Membrane

Workable

Only relevant if the upper slope is genuinely flat, which happens on some conversions.

What we check first

The failure points that are specific to this shape, in the order a roofer looks at them.

The break line where the two slopes meet, which is the defining leak point on this shape.
The pitch of the upper slope, measured not estimated.
Dormer valleys and flashing.
Whether fasteners on the steep lower slope are holding, since gravity works against them differently than on a conventional pitch.

What moves the price

Square footage is a poor predictor on its own. These are the things that actually change the number on this shape.

The break line between the two slopes is a fabricated detail on every run and adds real labor.
The steep lower slope usually requires fall protection and staging, which raises the labor rate.
Two pitches can mean two different underlayment specifications on the same roof.
Dormers are common on gambrels, and each one adds valleys and flashing.

Get this roof inspected Roof repair Roof replacement Storm damage

Common questions

Can you put asphalt shingles on a gambrel roof?

Yes on the steep lower slope without qualification. The upper slope is the question: under the 2018 IRC, section R905.2.2, shingles need at least 2:12, and from 2:12 up to 4:12 the code additionally requires the low-slope double underlayment application. Plenty of gambrel upper slopes land in that range, so the pitch needs measuring.

Why does my gambrel roof leak in the middle?

The break line is the hardest detail on a gambrel. Water coming off the shallow upper slope hits the transition and changes speed and direction there. If the transition was shingled straight through without a proper detail, or the underlayment was not carried correctly across it, that is where it shows up first.

Is a gambrel roof more expensive to replace?

Per square foot, usually yes. The steep lower slope needs fall protection and slower work, the break line is a fabricated detail on every run, and the upper slope may need a different underlayment specification. The upside is that gambrels often sit on smaller footprints than the space inside suggests.

More answers on the roofing questions page, or see every roof shape side by side.

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