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Updating Historic Homes Through Compatibility and Differentiation

When it comes to updating historic homes, there are a lot of routes you can take. Many approaches to designing remodels and additions of historic homes seek to balance two concepts: compatibility and differentiation. Let’s explore what these concepts mean and how do they play out in design.

February 1, 2024

At Board & Vellum, we pride ourselves on working on many of the beautiful, historic homes in Seattle and the greater Pacific Northwest. Each project comes with its own set of unique qualities and characteristics, from the style and age to neighborhood location. And each characteristic contributes to a home’s unique historic character and charm.

When approaching the design for an addition or remodel of a historic home, we take many factors into consideration. We always evaluate historic homes within their context – style, neighborhood, era, to name a few – to determine the best approach. But, like all projects, there are many places we can take the final design. In this post, we’ll be exploring compatibility and differentiation, two important concepts when it comes to updating historic homes.

What are the rules for adding onto a historic property?

The generally accepted rule when adding a contemporary addition to a historic building is that new work should be differentiated from the old but compatible with the three essential elements of the original design.

  • Massing, or the solid forms and blocks that make up a building.
  • Scale, or the proportional relationship of building elements to one another.
  • Size, or the physical width and height of building.

Considering how these elements interplay is meant to protect the integrity of the original historic elements. But you know us. We don’t always do the generally accepted thing.

Breaking the Rules

The two concepts of compatibility and differentiation are at the heart of all historic remodels and additions. But when a home or building isn’t a listed landmark, we have more freedom to explore these in the design.

Whenever possible, we try not to be prescriptive. There are always exceptions and unique circumstances we take into consideration. No matter our approach, the goal remains the same for all remodel projects, historic or not: for the new work to complement, rather than detract, from its surroundings.

How do compatibility and differentiation look in practice?

What do compatibility and differentiation mean when considering an addition or remodel to a historic home? It’s complicated. The definitions of “different” and “compatible” vary widely among architects, with a lively, centuries-old debate on best practices.

Today, we generally follow one of four distinct methods for balancing the ideas of “different” and “compatible.” Each of these methods falls along the “different” and “compatible” spectrum, for widely different results. (Read Steven Semes’ 2007 article on the subject for a fascinating – yet nerdy – view on this topic.)

Literal Replication

The first method is Literal Replication. This refers to using the same materials, style, and design exactly as in the original. This leads to an addition or remodel that seeks to blend in seamlessly with the original building. Literal replication is at the heart of the debate on differentiation.

Bungalow West: Second-Floor Addition to a Bungalow – Exterior Street View
An Example of Literal Replication

For our Bungalow West project matched the second-floor addition to the original style of the home. The addition adds valuable square footage without detracting from the original design.

We’ve used literal replication in a case where a building was severely damaged by fire and in other modestly scaled additions.

In theory, preservationists tend to avoid replication on projects with historical significance as it can blur the lines between new and old. The feeling is that this blurring will detract from the integrity of the original building. But in practice, literal replication provides compositional unity and can subtly add to the building’s history, rather than place a contemporary stamp on it.

Invention Within a Style

Next up is invention within a style. This method involves taking direct inspiration from the existing historic features and contemporizing them just enough in the new work to look current and updated, but still fits well visually into the existing context and with the same architectural language.

Modern Interpretation of a Classic Farmhouse – Foothills Retreat: Rendering from Driveway – Board & Vellum
An Example of Invention Within a Style

In the Foothills Retreat, old and new stand out equally in a natural balance.

Invention within a style is common among Seattle additions and remodels, and many of our clients with historic homes go this route. It can provide an ideal balance between compatibility and differentiation. We love it for the many design possibilities it offers and its unique ability to marry old with new without detracting from either.

Abstract Reference

Abstract reference is a method that seeks to maintain a visual connection in the design through light inspiration from the original building or historic context. We see this technique displayed more frequently on larger buildings, such as in multifamily or commercial settings, rather than in single-family homes. But single-family homes can also be great examples of this of this method!

Shelby House – Custom Home Design by Board & Vellum
An Example of Abstract Reference

Though the forms and features of Shelby House have all the hallmarks of a historic home, the materials and style feel modern.

Rather than ignore the historic design elements of the original structure, abstract reference will reference these elements with new materials or in a new style. An example of this might be maintaining the same window rhythm, size, and spacing, but in a totally new, contemporary design style. It’s a way to add new design elements to a remodel or addition without completely ignoring the historic context.

Intentional Opposition

Intentional opposition is perhaps the most widely known method for adding onto a historic structure. Probably because it’s one of the most obvious! Think: Frank Gehry (who designed MoPOP) and REM Koolhaas (who designed the iconic Seattle Central Library). Or less vividly, imagine you see a historic stone or brick library with a glassy, modern addition. That’s intentional opposition. (Though, it could be Abstract Reference, too, depending on the design!)

Modern Kitchen in a Craftsman Home – Board & Vellum
An Example of Intentional Opposition

For the kitchen remodel and addition on this home, we opted for a modern box form (hence this project’s name: Modern Kitchen in a Craftsman Home). It doesn't hide or attempt subtlety – it stands out on purpose.

Intentional opposition doesn’t reference the historic structure at all, or it plays up the differences between old and new.

We know how great a well-considered addition can look, even when it’s quite different from the look of the original home. Across the board, intentional opposition can be aesthetically successful, and lead to some interesting and beautiful juxtapositions. It can look out of place within its context – but sometimes that’s the point!

Which approach is right for you?

Wherever you fall on the compatibility and differentiation balance, there no one right answer for how to add to your home. (There is a lively debate between modernism and contextualism for those who really want to nerd out on architectural theory!) But we can help guide the design process to a beautiful and functional outcome. Each of the methods mentioned in this post has its place and each one comes with its own set of advantages and challenges. Whatever your preference (even if it’s none of the above), we’d love to work with you to find the right approach for your tastes and situation!


This post is part of a series about what you should know when updating an historic (or just an old) home.

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Updating Historic Homes Through Compatibility and Differentiation

When it comes to updating historic homes, there are a lot of routes you can take. Many approaches to designing remodels and additions of historic homes seek to balance two concepts: compatibility and differentiation. Let’s explore what these concepts mean and how do they play out in design.

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