Gambrel Roof Slope

Check overhang to calculate rafter overhang equal to the lower level cut at the full rafter depth.

Gambrel roof slope.

A roof with the shallow slope below the steeper slope at the eaves. A gambrel style is often called a barn roof. Anything less than this will ultimately result in a roof that leaks if you plan on putting shingles on it. A gambrel or gambrel roof is a usually symmetrical two sided roof with two slopes on each side.

A gambrel or a barn roof is much like mansard in a sense that it has two different slopes. Besides its unique appearance a gambrel roof also serves to maximize the usable floor space in the attic area. The rule of thumb that i use when designing a gambrel is that the top pitch should be no less than half the pitch of the bottom. The usual architectural term in eighteenth century england and north america was dutch roof the upper slope is positioned at a shallow angle while the lower slope is steep.

A gambrel or barn style roof is simply a gable roof with a change in slope partway up the roof. A gable roof has only two rafter or truss chord angles a top cut at the peak and a bottom cut at the walls. Move slider or directly enter angle to alter sweep angle of lower rafters and change the shape. This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.

It also shows you various heights along the interior of the sloped gambrel ceiling ie. Well let s face it it s a very attractive roof design but there are practical considerations as well. The shallower the top pitch the more squatty it will look. Similar to mansard the lower side of the gambrel roof has an almost vertical steep slope while the upper slope is much lower.

In other words if you start with a say 14 12 bottom pitch your top pitch should be 7 12 or greater. When you are designing your shed roof whether it be a gambrel gable or saltbox you should never have any roof pitch less than a 3 12. This means that for every 12 horizontal run you must have at least 3 of rise. If at all possible it looks the best at exactly half.

Maximum height in the center height at the pitch break how far in from the side wall a six foot height occurs etc. Compare with bell roof. A roof similar to a mansard but sloped in one direction rather than both. The difference between the two is that the gambrel only has two sides while the mansard has four.