If you need to replace your shingles or add a new roof on your home, then you’ll need to learn how to measure a roof for shingles. You can approach the task in two ways. The first method allows you to estimate roof square footage without going up on a ladder. To use the second method, which is the most accurate, you’ll need to climb on your roof.
How to Measure a Roof for Shingles Steps
For the estimation method:
- Measure the width and length of every room in your home that is directly under your roof, including garages and covered porches.
- Multiple each room’s width and length individually to find square footage.
- Add the square footage of all spaces to arrive at total square footage.
- Enter your attic with a level.
- Hold the level against the bottom of a roof rafter and make a mark 12 inches up the rafter.
- Keep the level against the bottom of the rafter while lowering it into a horizontal position.
- Stop the level once it shows that it’s level.
- Measure up from it vertically to the point you marked on the rafter.
- Record the vertical measurement on paper as the ratio X/12.
- X represents the vertical dimension.
- 12 represents the 1 foot mark.
- Find a slope factor chart on the internet to obtain the slope factor for your ratio.
- Multiple total square footage by the slope factor.
- Pad this figure by 5% (multiple by 1.05).
For the actual measurement method:
- Draw a general representation of your roof showing every surface plane.
- Secure a ladder and climb onto the roof while wearing nonskid shoes.
- Measure the width and length of every section of the roof.
- Record the dimensions for each section of roof on drawing.
- After gathering all measurements, begin calculations.
- Multiply the lengths and widths of each section to determine square footage.
- Add all individual square footage results to get the total square footage.
- Multiply the total by 5% (1.05).
- Use this final figure to select quantities of shingles and rolls of roofing paper.