Why In-Kind Materials Matter in Historic Preservation

“In-kind” is one of the most important — and most misunderstood — terms in historic preservation. It gets misused constantly in construction, design, and project descriptions.

But in preservation, “in-kind” has a very specific meaning: a repair or replacement that matches the original material in composition, profile, craftsmanship, appearance, and performance.

Close is not in-kind. Similar is not in-kind. “Looks the same from 30 feet away” is not in-kind.

Historic buildings rely on material compatibility to function as designed. When you substitute modern products without true equivalency, you may inadvertently accelerate deterioration, distort historic character, or trigger system failures.

Why “In-Kind” Is Central to the Secretary of the Interior’s Standards

The Standards emphasize retaining historic fabric and using in-kind materials for good reason:

• They protect the building’s physical integrity

• They preserve character-defining features

• They ensure repairs age and perform predictably

• They prevent incompatible materials from creating new failures

“In-kind” isn’t an aesthetic preference — it’s a technical requirement rooted in hundreds of years of building science.

What True In-Kind Repair Requires

Authentic in-kind repair is a discipline. It means:

1. Accurately identifying the original material

You must know precisely what you’re matching, whether it’s:

• A specific wood species (e.g., old-growth redwood vs. modern redwood)

• A lime-based mortar mix

• A hand-forged hinge

• A plaster formulation

• A molding profile

• A paint type or coating

This often requires field observation, testing, and sometimes lab analysis.

2. Matching craftsmanship and details

Historic craftsmen left distinct marks in their work:

• Plane marks on carpentry

• Scribe lines

• Hand-cut joinery

• Variable paint film thickness

• Tooling patterns in mortar

Your repair shouldn’t look machine-tooled or “perfect.” It should look correct.

3. Matching performance, not just appearance

Material behavior matters:

• Moisture permeability

• Expansion/contraction

• Density

• Fastener compatibility

• Movement tolerance

A mismatch here will cause failure, even if the repair looks fine at first.

4. Fabricating when necessary

In-kind doesn’t always mean off-the-shelf. Often, it means:

• Custom milling

• Specialty carpentry

• Casting replacements

• Matching historic glass

• Replicating hardware

The best preservation contractors know how to source or create what’s needed.

Why “Almost In-Kind” Is Often Worse Than Replacement

Small differences compound. We see failures caused by:

• Modern redwood shrinking or decaying faster than old-growth

• Cement mortars cracking historic brick

• PVC trim trapping moisture behind siding

• Pressure-treated lumber corroding traditional fasteners

• Synthetic caulk sealing assemblies that need to breathe

These mismatches may not be obvious at installation, but they become expensive issues a few seasons later.

In-Kind Repair Is Preservation at Its Purest

It protects the authenticity of the resource, ensures durability, and maintains trust with the community and owners. It’s not nostalgia — it’s responsible building science.

Treeline approaches in-kind repair as the default, not the exception. Because when you honor the original materials, the building honors your work back.