Historic sheet metal restoration · Lesson 1 of 4

Historic sheet metal restoration: principles and terminology

Why an old building is a record, the four federal treatments, how in-kind replacement and compatible substitutes differ, the historic sheet metals from tinplate to zinc, where a fabricator fits, and the lead and fire boundaries.

You will be able to: Define the four treatments, repair before replacement, in kind and substitute, name the historic sheet metals and tell them apart, state where AFS fits, and name the lead and fire boundaries of work on old metal.

11 min · 11 slides · 9 questions

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Slide 1 of 11

The building is the record

Standard 3 says each property shall be recognized as "a physical record of its time, place, and use."

Standard 5 calls for preserving "Distinctive features, finishes, and construction techniques or examples of craftsmanship."

A cornice, a cupola or a painted tin roof is often exactly that kind of feature.

Sources

The Secretary of the Interior's Standards for Rehabilitation (the ten standards; codified in 36 CFR Part 67 for the tax incentives program) - U.S. National Park Service, Technical Preservation Services

Glossary

Character-defining feature: A feature, finish or construction technique that gives a historic property its character; the Standards for Rehabilitation call for preserving distinctive features, finishes and examples of craftsmanship.
In kind: Replacement in which the new work matches the old in material, design, scale, color and finish.
Compatible substitute: A different material that matches the historic one in appearance, has similar physical properties or is installed to tolerate the differences, and performs over time; it is used only when replacing in kind is not possible.
Terneplate: Sheet iron or sheet steel coated with a lead-tin alloy; duller than tinplate and often confused with it in records.
Tinplate: Sheet iron or steel coated with tin, used for historic roofing, shingles and siding.
Galvanized iron: Iron or steel coated with zinc; it is magnetic, unlike pure zinc, so a magnet can tell them apart.