Architectural Flashing Supply
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AFS Design Center · Calculators

Method sheet

Custom Flashing Profile & Bend Development

A profile of straight legs and bends, with optional end hems. Blank width, bend schedule, bend lines, weight, and a check against AFS fabrication limits.

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SheetM-flashing-profile

Method

flashing-profile 1.2

Engine

1.1.0

Output status

Informational

Review

Awaiting review

Formulas

  • Sharp-corner girth (AFS quoting blank) = sum of legs + hem allowances
  • Bend allowance BA = theta x (R + K x t)
  • Setback SB = tan(theta / 2) x (R + t) where the dimensioned face is outside the bend (outside setback), tan(theta / 2) x R where it is inside (inside setback)
  • Bend deduction BD = 2 x SB - BA; developed blank = sum of legs - sum of BD + developed hem allowances
  • Quoting hem allowance (sharp girth): open = 2 x length + gap; closed = 2 x length (AFS / FlashDraft convention, awaiting AFS confirmation)
  • Developed hem allowance (bend deduction): return length + pi x (Rh + K t), Rh = 0 closed, gap / 2 open
  • Weight = blank x piece length x mass per area

Conventions

  • Legs are mold-line lengths to the theoretical sharp corner, dimensioned on the face outside the first bend.
  • theta is the TURN angle (180 deg minus the included angle). 180 deg folds are hems.
  • Thickness is the published nominal thickness for the gauge or weight, never a guess.

Limits - what it will not do

  • No default K-factor or radius: the bend-deduction model needs both entered, and its result is preliminary until AFS calibrates them.
  • Neither model is a fabrication-ready flat pattern until AFS shop review.
  • Profiles that cross, touch or run along themselves (non-adjacent legs in contact), 0 or 180 deg bends and legs too short for the radius are refused; legs closer than the metal thickness are flagged.

Who must review it

  • AFS fabrication lead: calibrate K-factor and inside radius on the AFS brake from measured coupons

Worked example

Inputs 2 in + 2 in at 90 deg, R = 1/16 in, K = 0.44, 24 ga galvanized (t = 0.0276 in)

Expected BA 0.117251 in, OSSB 0.0901 in, BD 0.062949 in, blank 3.937051 in

Checked by an automated test on every change.

Sources

  • AFS fabrication limits - Architectural Flashing Supply, read 2026-10-15

    Shop limits confirmed by AFS: max piece 10 ft 6 in, max girth 48 in, end flange 1/2 in, leg between bends 3/4 in, hem 3/8 in; material and gauge bend rules.

  • AFS quote convention - Architectural Flashing Supply, read 2026-10-15

    A 10 ft x 4 ft sheet; strips are cut along the 10 ft length, so strips per sheet = floor(48 / blank width).

  • Bend allowance from neutral-axis arc length (geometric derivation) - Method sheet flashing-profile/1.0, read 2026-10-16

    BA = theta x (R + K t); outside setback OSSB = tan(theta/2) x (R + t); bend deduction BD = 2 OSSB - BA. Geometry only - K must come from calibrated shop samples.

  • Galvanized sheet metal weight chart by gauge - MEP Academy, read 2026-10-16

    Galvanized gauge thickness and weight including zinc coating, e.g. 24 ga 0.0276 in, 1.156 lb/ft2. AFS to confirm against mill certificates.

  • Sheet metal gauge chart - stainless steel (U.S. Standard gauge) - MachineMFG, read 2026-10-16

    Stainless gauge thickness: 26 ga 0.01875 in ... 16 ga 0.0625 in. AFS to confirm against mill certificates.

  • Copper in Architecture Design Handbook - Fundamentals: Dimensions (Table 1.2B) - Copper Development Association, read 2026-10-16

    Sheet copper nominal thickness by weight: 16 oz 0.0216 in, 20 oz 0.0270 in, 24 oz 0.0323 in, 32 oz 0.0431 in.