Eaves are the lower edges of a roof, also considered the gutter line. This creates an overhang that goes beyond your home's exterior walls, increasing a roof's square footage. The overhang will not be accounted for in your home's square footage.
The steeper the pitch, the greater the amount of additional square footage. The rafters will also need to be longer to cover the span once they're pitched at the angle of the roof. The easiest way to calculate a pitch adjusted measurement is by using pitch conversion multipliers.
Most jurisdictions will allow the roof line of overhang the setback line as long as it is still overhanging your own property. However, most jurisdictions also have different views on how much the will allow.
A method to calculate the correct overhang to provide the proper shading is to multiply the distance from the sill of the glass to the soffit by a factor based on the angles of the sun.
To find your roof's total square footage: Measure the length and width of each plane on the roof (including dormers) then multiply length times width. Add the square footage of each of the planes together. For example, this shed roof has one roof plane.
Attics, garages, and other unfinished spaces do not count towards your home's square footage. However, if there is no other level above, they still need to be roofed. Attic spaces can also increase a roof's height and angle, which would increase the overall square footage.
Square Footage of Your Roof:
So a trick to estimate your roof size is to multiply the square footage of your house by 1.5 (ex: A 2,000 square foot house will have a roof that is approximately 3,000 square feet).
For the eaves, which are the lower edges of the roof, the overhang should be between 12 and 18 inches. This means the roof should stick out 1 to 1.5 feet past the walls. For the rakes, which are the sloped edges of the roof at the gable ends, the overhang should be about 8 inches.
To calculate the area of each section of the roof, multiply the length and width measurements for that section. For a gable roof, multiply the length and width of each triangular section and divide by 2 to get the area of each section.
For example, a roof with a span of 20 ft and a rise of 7 feet needs rafters that are the square root of 400 + 49 = 21.2 feet. This does not include the extra length required for the overhangs.
Lot Coverage. The total area of a lot covered by the principal and accessory buildings, or structures including any area occupied by overhangs or roofs and any attachment to a building or structure, but excluding (a) open decks less than 30 inches in height.
If it's a few stories up, the underlying owner could make use of the ground under the overhang and an air space easement would be appropriate. If your talking about an overhang two feet above ground, there's not much practical use of the ground below, so an easement from the ground up would be appropriate.
These architects use the Golden Ratio, or a roof pitch with a ratio of about 1:1.62, as a benchmark to test their intuition on an unsatisfactorily-designed roof.
A roofing square is an area of roof that measures 10 by 10 feet to make up a total of 100 square ft. This critical unit of measurement helps your contractor determine how much material they'll need to order for your roofing project, from underlayment to bundles of roof shingles.
Eave and rake overhangs should be measured from the exterior edge of the fascia to the exterior edge of the wall. Xactimate will require these measurements for each roof section of roof.
In most climate conditions the following formula can be used to determine the appropriate amount of overhang: X=1/2Y (where X is the length of the overhang required and Y is the distance from the bottom of the door to the base of the overhang.)
For starters, make sure you design your island with enough space underneath the counter for your knees. Generally speaking, a countertop overhang of 12-18” is a good place to start.
Shingles should not extend more than 3/4” (19 mm) past the drip edge. If shingles overhang the edge of the roof by more than 3/4” (19 mm), then they are not supported and may crack and break off.
The most common countertop overhang measurement seen in homes today is one and a half inches. This is considered the ideal measurement because it creates the perfect place for people to rest their forearms while preparing food.
The ideal length of overhang is around 150mm. We allow an additional 300mm of EPDM in our shed roof kits to ensure an even overhang on all sides.
Multiply your house length by your house width to get the area. (For example, 40 feet x 30 feet = 1,200 square feet.) Next, multiply the area by your roof's pitch. (1,200 x 1.05 = 1,260 square feet.)
In general, most roofs will last between 20 and 25 years before they need to be replaced. If your roof is approaching or has already reached this age, it's time to start considering a replacement. When a roof gets older, it becomes more susceptible to damage from storms, wind, and hail.