Hems, returns, locks and seams · Lesson 2 of 4

Hems, returns, locks and seams: materials, standards and design constraints

The AFS limits that decide whether a hem can be made, the copper seam rules in the CDA details, and why painted coil has its own bend rating.

You will be able to: Apply AFS's hem limits by material and thickness, the CDA copper seam rules, and a coil maker's bend rating, each to the work it belongs to.

10 min · 11 slides · 8 questions

All lessons in this module

Slide 1 of 11

AFS hem limits

The shortest hem return AFS forms is 0.375 in; FlashDraft blocks anything shorter.

The standard return is 0.5 in, the length FlashDraft gives a new hem. The shortest end flange is 0.5 in.

These are what AFS's folder makes, not an industry standard.

Sources

AFS fabrication limits - materials, thicknesses, bend rules and sizes the shop can make - Architectural Flashing Supply
FlashDraft hem types and starting dimensions - Architectural Flashing Supply

Videos for this lesson

What this video shows: The Copper Development Association prepares and solders a copper flat seam, the joint used on flat seams up to a 3:12 slope.

Video: How-To: Flat Seam Soldered Joint by Copper Development Association, on YouTube. Chosen from the video's published description.

Glossary

Girth: The flat width of the blank across all the legs and hems; AFS's maximum includes the hems.
Cleat: A strip locked into a seam and fastened to the structure, holding the sheet while letting it move.
Pretinning: Coating the edges of copper sheets with solder before the seams are formed.
T-bend: A coating-flexibility rating for a 180 deg bend (the ASTM D4145 test), stated in multiples of the metal thickness T; each coil maker publishes its own ratings.
Shop review: An AFS status: the profile can be ordered, and the shop confirms it before fabrication.