Roof flashing fold development calculator

Calculate flat blank width and blank lengths per run including laps with your own figures.

Your numbers

Use the units shown. Results update as you change valid inputs.

Use flat blank width and blank lengths per run including laps to compare changes to your inputs. The method and limits below explain the scope.

Examples

Examples

Try the starting example

Developed straight profile legs (mm)
100,80,40
Supplied bend additions (mm)
2,2
Run lengths (m)
5,4
Specified end lap per extra stock piece (m)
0.1
Available stock blank length (m)
2.4
Flat blank width (mm)
224
Blank lengths per run including laps (m)
[[5,3,5.2],[4,2,4.1]]
Total developed blank area (m²)
2.0832

Try another scenario

Developed straight profile legs (mm)
120,80,40
Supplied bend additions (mm)
2,2
Run lengths (m)
5,4
Specified end lap per extra stock piece (m)
0.1
Available stock blank length (m)
2.4
Flat blank width (mm)
244
Blank lengths per run including laps (m)
[[5,3,5.2],[4,2,4.1]]
Total developed blank area (m²)
2.2692
Calculation method

Calculation method

Flat blank width (mm)

sum(a)+sum(b)

Blank lengths per run including laps (m)

J([[v,max(1,ceil((v-d)/(e-d))),v+max(0,ceil((v-d)/(e-d))-1)*d] for v in c])

Total developed blank area (m²)

(sum(a)+sum(b))/1000*sum(v+max(0,ceil((v-d)/(e-d))-1)*d for v in c)

Symbols and units
a
Developed straight profile legs (mm)
b
Supplied bend additions (mm)
c
Run lengths (m)
d
Specified end lap per extra stock piece (m)
e
Available stock blank length (m)

Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.

Calculation steps and notation

sum(list) adds all entries in the list.

Assumptions & limits

Assumptions & limits

  • Supplied bend additions encode approved neutral-axis allowances. Stock length>lap≥0. No automatic bend deduction or metalworking design. Supported limits: All numeric inputs must be finite. Only the explicitly described mathematical scenario is supported.
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