A Gambrel roof has a symmetrical two-sided structure with 2 gradients on each side. The lower slope is very steep, usually around 60 degrees while the upper slope has a much shallower angle, approximately 30 degrees. The Gambrel roof is often compared to a Mansard roof due to the 2-slope structure with the main difference being Mansard roofs have 4 sides while Gambrel roofs have only 2 sides.
This design is commonly used for barns and stables in USA due to the shape allowing for extra storage room. This style of roof is also frequently found in churches and houses as the design became popular in the Dutch colonial and Georgian eras.
When being used as a habitable space, Gambrel roofs will need windows to increase the amount of natural light and make the room feel bigger. Windows are easy to install into a Gambrel roof due to the shallow, lower slopes which act as walls for the windows to be mounted on. Often, roofers will choose to install dormer windows to provide greater structural integrity however windows can be installed directly into the slopes of the roof. Skylights can also be added to the steep upper slope to open up the room even further.
The name ‘gambrel’ originates from the resemblance to the contour of a horse’s hind leg, often referred to as a hock or gambrel in western cultures. However, this style of roof is believed to originate in Southeast Asia and adopted by Dutch traders in the colonial era.
The Dutch then brought this unique design to the west, proving especially popular in the USA, although can be seen throughout Europe as well. The oldest known Gambrel roof can be found at Harvard University on the second Harvard Hall dating back to 1677.
Constructing a Gambrel Roof
When building a roof, no matter what style you choose, it is always important to consider the materials needed for constructions. Due to its versatility, many materials can be used to construct a Gambrel roof although the best material to use is metal as it is the strongest option and more durable resulting in less maintenance and a longer life.
Some roofers choose to use asphalt or wood shingles when constructing a Gambrel roof due to its more stylish look. Not only this but these materials tend to be quieter during rain making them better for inhabitable spaces. However, wood and asphalt are more expensive to buy and are more prone to damage leading to higher maintenance costs in the long term.
It is also important to consider the direction the flat facing sides of a Gambrel roof will be pointing during construction to avoid the effects of weathering. If you are unsure of the best direction for your roof, seek advice from a contractor regarding the best orientation for your area.
- Maximises Space – The shape of the Gambrel roof maximises headroom and shortens the height of the roof providing more usable space while not adding extra height to the structure. Extra space on the top level makes buildings with Gambrel roofs perfect for storage as well as creating a habitable space.
- Less Materials Needed in Construction – Gambrel roofs require less materials during installation as the slopes do not require support beams or columns. This means the less money is spent on materials and installation is faster so labour costs are lower. This makes Gambrel roofs a more affordable option than alternatives, such as Mansard roofs.
- Easy to Build – On top of needing less materials, the simple design of a Gambrel roof makes it incredibly easy to construct. Due to this most roofers are still able to construct a Gambrel style even though they are less common than a pitched roof.
- Good Drainage – The steep sloping sides of a Gambrel roof allow for good drainage during rainfall as the raindrops simply run off the sides without getting caught. This reduces the instances of leakages and water damage, reducing maintenance costs in the long term, similar to a Gable roof.
- Traditional Look – As this style of roof was popularised in the Georgian era, the Gambrel roof is a historical design adding value to newer buildings with a traditional look.
- Long Lasting – When the proper materials are used during construction and regular maintenance is completed to a high standard, Gambrel roofs will last over a century without needing refurbishment making it a much desirable roof structure to have if you are on a small budget.
- Poor Resistance to Snowfall – Although the sloped shape of a Gambrel roof is beneficial during rainfall, the flatter upper slope causes problems during snowfall. Heavy snowfall over long periods of time will result in a build-up of heavy snow eventually resulting in roof collapse.
- Wind Damage – Snow isn’t the only weathering issue Gambrel roofs face; the shape of the design makes it more susceptible to wind damage as the air cannot flow smoothly over the steep surface of the lower slopes. In cases of extreme winds, such as hurricanes and tornados, the roof may even be lifted off. This is why it is important to consider the direction of the Gambrel roof during construction.
- High Maintenance Costs – Due to the high likelihood of weathering, annual maintenance checks are recommended for Gambrel roofs. This results in high maintenance costs, especially if damage has been sustained. Maintenance costs can be reduced by using sturdy materials, such as metal, during installation and having reinforced trusses to support the structure.
- Difficult to retro fit – While they are easy to construct on new builds, the unique shape of a Gambrel roof can prove expensive and challenging to install on an existing building. This means they are not ideal for those looking to convert their loft or upgrade their current roof-space.
Overall, Gambrel roofs are a stylish design to maximise roof space at a low cost for new builds. However, they do require extra attention during maintenance and are best in temperate climates without weather extremes. Nevertheless, this type of roof structure is a worth while investment with them being long lasting and good drainage to prevent any water damage.