TMT, tubes, roofing, cement & blocks
Cover width vs overall width
Grades, sizes and the unit each material is priced in.
Answer
Why do roofing sheets need effective cover width?
Explanation
The two figures
Overall width is what you measure across a loose sheet. Effective cover width is what one sheet actually covers once the side lap is in place. Cover width is always smaller.
Cover width comes from the profile specification, not from a tape measure.
Detail
What else the count depends on
The number of rows down the slope, which follows the slope length and the sheet length. Where the slope is longer than one sheet, sheets lap end to end and the overlap comes off the covered length too.
Detail
What the estimator does not do
It gives a preliminary sheet count. It takes no account of pitch, purlin spacing, wind loading or structural requirements, and it is not a roof design.
Questions
Also asked
Where do I find the cover width?
On the profile specification for the sheet you are buying. If you tell us the profile, it can be confirmed with the quotation.
Should I add an allowance?
That is yours to decide, and the estimator adds nothing unless you enter a figure. Cutting at hips and valleys usually justifies one; a simple rectangular roof may not.
Next
Ready to specify it?
Calculate the weight, add the lines and send one structured quotation request.