Add 1 2 inch or 1 inch to this measurement depending on gutter length and mark the fascia.
How to measuring tape gutter slope.
The steeper a roof s pitch the more windblown rain it can collect.
Hold one end of the level against the roof level it and then measure the distance between the roof and the underside of the level at its midpoint which gives you a 12 inch run.
It should pitch from the middle toward the downspouts at each end.
Make a mark with chalk and record the measurement.
Mark the measurement with a piece of tape and then pull the twine off of the other end of the gutter.
Run the tape measure from 1 corner of the gutter as far as you can go toward the opposite corner.
Carefully climb down the ladder and move it to the chalk mark.
Start on the end of the gutter farthest from the downspout and measure the space from the roof edge to the top of the gutter.
Use a tape measure to mark a second spot 10 feet closer to your downspout checking that the line between the two marks is level as you go.
You can move along the roof bringing the twine to the other end of the gutter run.
There s no hard rule on the angle of the slope.
This means the downspout end of the gutter should be set 3 4 of an inch lower than the other end.
This second mark should be at least half an inch higher than the first one.
Otherwise it s a sign that your rain gutter slope isn t sufficient and needs adjustment.
As long as there is enough slope the water will naturally run out.
Measure from the roof edge at both ends of the gutter if you want to be sure.
Take the same measurement at the opposite end near the downspout.
You can measure pitch with a 2 foot level and a tape measure.
Measure the length of each gutter run.
A good guideline is that the pitch should cause a decrease somewhere between 1 to 2 inches over a 40 foot run.
Use your tape measure to determine the length of the twine marking down this calculation.
For example if you have 30 feet of guttering the calculation is 1 4 x 3 0 75 i e.
Mark the measurement on the fascia board.