Quick Reference: Weight of Water per Inch per Square Foot
The following table provides the weight of water per inch per square foot in pounds. One cubic inch of water weighs 0.036127 of a pound. One square foot of water one inch deep weighs 144 times this, or 5.202288 pounds. Everything else has been calculated from this.
This table should give you an idea of how much of a live load is being added to your roof by areas of ponding water or clogged drains. (Also see Roof Online’s Roof Drainage page.)
Values for areas or depths not covered in the table should be easy to arrive at simply by adding together values for areas or depths which are covered.