Q&A for How to Build a Gambrel Roof

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  • Question
    What is the length of each board for a roof to fit a twelve-foot-wide building?
    Community Answer
    12/2.73 will get you dang close. Don't forget to figure if you want that as outside or inside.
  • Question
    How do I measure for a barn?
    Community Answer
    If you want to do these pitches, you just need the width. Don't forget to include any overhang and make sure you input measurements as a single number (2.25' instead of 2'3"). Span/(2.73) will get you equal parts at these angles. For overhang, you'll have to use a 30-60-90 to figure out the added width.
  • Question
    What is the length of each rafter component on a gambrel roof?
    Community Answer
    It depends on the span of the walls. The easiest way to understand this is to compare a simple gable roof. You won't know the length of a rafter if you don't know the distance from wall to wall, or the pitch of the roof.
  • Question
    What size are the plates at the joints?
    Community Answer
    The plates are recommended to be about half the length of one support.
  • Question
    Can I put a gambrel roof on my house?
    Community Answer
    Yes, provided you follow local building bylaws and codes. Some areas prohibit the use of rafters and only allow pre-engineered trusses. Some areas allow rafters provided they have been designed by someone proven to be competent in their design (usually this is an experienced and skilled carpenter or an engineer).
  • Question
    How do I put shingles on a 60 degree dog-leg roof angle?
    Community Answer
    If you have an extension ladder that can reach the top of the lower roof section, then you can shingle right off the ladder. If not, you will have to buy or borrow roof jacks for the pitch you are working on, and roof it like any other steep pitched roof.
  • Question
    Should I build an overhang with this roof?
    GEttinger
    Community Answer
    You can build an overhang to help with drainage, but because of the angles on the roof, it's not always necessary.
  • Question
    Where can I buy just the brackets for a building with a gambrel roof?
    Community Answer
    Try going to a local hardware store. They should have some. If not, order them online.
  • Question
    I have a 20 x 30 building that I want to put a gambrel roof on. How do I determine the angles of the trusses?
    GEttinger
    Community Answer
    If you are constructing a roof for a structure that is larger than 12 feet long, you should consult a certified carpenter to help you with the construction of the roof. Otherwise, you can use the formulas found in this article to help determine the appropriate angle for your truss ends.
  • Question
    I only count six gussets per rafter. Two per joint, with three joints per rafter. The instructions call out for eight per rafter. What am I missing?
    Community Answer
    There is a mistake in the count. If there are only 3 joints (1 on each side and 1 at the peak), then there should only be 6 gussets per rafter assembly.
  • Question
    How do you make rafters for a gambrel roof?
    Drew Hawkins1
    Community Answer
    You'll need to cut rafter pieces so they're the right size. Start with 24 2x4 boards for the rafters. If your shed is 10 feet (3.0 m) wide, each full rafter piece will be constructed of 4 2x4 boards that are 4 feet (1.2 m) long. Count the number of wall studs you have. You’ll need a full rafter piece for each wall stud in your barn or shed. Then, line the pivot point on a speed square to the corner of each board at a 22.5-degree angle and mark it with a pencil. Both ends of each board should be marked this way. You'll cut along the lines that you make. Use a miter or a circular saw to cut the boards. Line the saw blade up against the line that you made. Press the trigger on the saw and lower it to cut off the ends of the boards at an angle. Once you’re done, the board’s ends should sit fit flush against each other.
  • Question
    Is a gambrel roof more expensive?
    Drew Hawkins1
    Community Answer
    Yes, they're usually more expensive to have built. A gambrel roof can involve using more materials and usually requires more labor to cut and assemble the wood. Both of these factors can drive up the cost. Additionally, a gambrel roof also uses extreme pitches, or angles, which can be tougher to assemble. There's also an increased risk of having wood fall while it's being installed. The extra danger can often cause contractors to charge more for a gambrel roof in order to account the potential risk of injury. But even if you build it yourself, the additional materials and equipment you'll need to get the job done can make it more expensive than a standard roof.
  • Question
    What is the advantage of a gambrel roof?
    Drew Hawkins1
    Community Answer
    A gambrel roof is commonly used on barns and sheds. They have 2 slopes on each side of the roof and have high ceilings. The reasons they're used for barns and sheds are pretty straightforward: more storage space! The shape of the roof gives you more room for storage without taking up any additional space. It's also the reason mansard roofs and gambrel roofs are used. The design allows for more room while still having a sturdy covering that will last for a long time.
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