Use this construction calculation for preliminary quantity, geometry, material, load, or coverage planning when dimensions and units have been measured consistently.

Valley plan length (m)

Required number input.

Vertical rise (m)

Required number input.

Estimate straight flashing length along a roof valley from its horizontal plan projection and vertical rise. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Straight valley length (m)

The resulting straight valley length returned as a number.

• Drainage and flashing dimensions depend on catchment, rainfall, roof or surface geometry, outlet capacity, material, climate, and local detailing. Confirm slopes and terminations against the complete water-management design.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Verify dimensions on site, use current product data and local code requirements, include an explicit waste or safety allowance where appropriate, and obtain qualified structural, electrical, plumbing, or geotechnical review when required.

• Theoretical Rafter Length

  Find the straight-line rafter length between eave and ridge from horizontal run and vertical rise; excludes overhang and cuts.

• Roof Pitch Angle

  Calculate a roof slope angle from vertical rise and horizontal run, not the rafter length.

• Drip Edge Length

  Total roof drip-edge material along measured eaves and rakes, including a waste allowance for cuts.