What Is The Minimum Roof Overhang?
What Is The Minimum Roof Overhang?
There is no true standard size for overhangs, but typical overhangs used for protection from rainfall are 16-18 inches wide. The overhangs wanted for shading should be minimally 24 inches.
More commonly, they are 36 inches wide or more. The size of an overhang is dictated by the cantilever or the horizontal projection of the roof beyond the vertical supporting wall.
The further the cantilever, the heavier the load on the supporting wall and the more the structure will cost. There are various ways to support a cantilevered roof. One is to use a beam, typically a wood member placed on top of the wall and projects out to support the end of the roof.
Another method of supporting a cantilever is through the use of a truss system. A truss system consists of two or more members connecting at the top and bottom and resting against the wall.
Trusses are typically made from wood, but you can also find metal rods that support a lightweight gable end on wood members.
Trusses are supported by posts made from wood or metal that extend out from either side of your house or on the outside wall. They project out in order to support the weight of your roof and help support trusses placed on them.
How Far Can You Cantilever A Roof Overhang?
The rule of thumb for cantilevered roof overhangs is that they can only extend up to 1/3 the length of the beam. However, it is more common for the overhang to be shorter.
Builders typically place the beams along the top of the walls and allow them to extend outwards. The reason for this is that cantilevered roof overhangs are more susceptible to wind damage than those that are not cantilevered.
It is also very difficult to install such overhangs because the rafters push against the exterior walls, making it increasingly difficult to finish those walls.
When a cantilevered beam is extended from a wall, the top is attached to a rafter that extends in the opposite direction from the beam.
For example, if you were to cantilever your front porch overhang 5 feet out from an exterior wall, your next rafter would extend away from the wall at least 14 feet.
This adds a lot of weight to your structure, so it’s best to use 2×8 or 2×10 joists and beams when framing this type of overhang.
How Do I Extend My Roof Overhang?
A roof overhang is fairly simple to increase or decrease. In order to accomplish this, you may cut the rafters in your present roof, install new rafters, and then cut trusses to fit in between the two rafters sections.
Here are some materials you will need to install an overhang on your roof, depending on the size of the overhang.
To extend a roof overhang:
- Locate the ridge beam and find a rafter beneath it by 1 foot.
- Position a level at the top of this rafter and draw a level line straight down to the outside edge of your house.
- Draw in new rafters (make sure they are perfectly perpendicular to your house)
- Cut out the existing rafters beneath each line you drew so you can install new ones
- Position these new rafters in their intended place
- Redraw your lines and use them to mark where you need to cut your trusses
- Cut these trusses to length using a miter saw
- Install the new rafters and place the trusses in between them
- Re-mark your lines at the end of the rafters and cut them down
