California is home to a remarkable inventory of historic buildings — Mediterranean Revival courthouses, Spanish Colonial estates, Craftsman bungalows, mid-century modern landmarks, and Victorian commercial buildings that define the architectural character of cities from San Diego to San Francisco. When these buildings require new or replacement doors and windows, the specification challenge is clear: preserve the historic character while delivering the structural performance, energy efficiency, and code compliance of contemporary construction.
Custom steel is, in many cases, the ideal specification for historic California buildings. Here’s why — and what you need to know to specify it correctly.
Why Steel Was Used Originally
Before the widespread adoption of aluminum in the 1960s and 70s, steel was the standard material for slim-profile windows and doors in significant commercial and residential buildings. The metal-sash windows in California’s historic courthouses, school buildings, and estate homes from the 1920s through 1950s were steel — fabricated with the same profile logic HERRERO uses today. Restoring or replicating these windows with the same material honors the original design intent in a way that wood, fiberglass, or aluminum cannot.
The Historical Line: Built for Restoration Work
HERRERO’s Historical Line features heavier profiles and divided-lite configurations that reference the visual language of traditional steel sash construction. Unlike the spare contemporary profiles of our Pure Line and Slim Line, the Historical Line carries the visual weight and detail density appropriate for traditional architectural styles — the kind of presence that makes a replacement window look like it belongs in a 1930s building rather than a 2020s specification catalog.
The Historical Line is used for historic building renovation, Craftsman-influenced contemporary designs, and any project where the design intent calls for architectural warmth and material presence rather than minimalist abstraction.
Historic Preservation Code Considerations
Buildings in California Historic Resource Registers or National Register of Historic Places listings may be subject to Secretary of the Interior’s Standards for Rehabilitation — federal guidelines that govern what can and cannot be changed in a historic structure undergoing rehabilitation. Windows and doors are among the most regulated elements under these standards, because they are character-defining features of most historic building types.
Key considerations for historic work: replacement windows and doors should match the original material, profile dimensions, and divided-lite pattern as closely as possible. Steel replacement of original steel sash is generally consistent with the Standards; replacement of original steel with aluminum or vinyl typically is not, because the profile dimensions and visual characteristics are different. Always coordinate with your State Historic Preservation Office (SHPO) contact or a qualified historic preservation consultant before finalizing specifications for listed buildings.
Energy Code Compliance for Historic Buildings
California’s Title 24 energy code applies to historic buildings in most permit situations, but the California Building Code includes provisions allowing alternative compliance pathways for buildings that are California or National Register listed. In some cases, the California Historical Building Code (Part 8 of Title 24) provides additional flexibility.
Even when standard Title 24 prescriptive requirements apply, custom steel with a full thermal break and appropriate Low-E glass can typically achieve compliance while maintaining the slim divided-lite profile characteristic of historic steel sash. HERRERO provides NFRC-certified performance data for historic-profile products upon request for energy modeling.
The Installation Challenge in Historic Buildings
Historic California buildings present installation challenges that standard new construction does not. Rough openings are rarely plumb, square, or level — they’ve had a century to settle. Wall assemblies are often non-standard: masonry without WRB systems, plaster on wood lath, or composite assemblies that don’t fit cleanly into standard installation method categories.
HERRERO installation specialists with historic renovation experience are available for complex California restoration projects. These specialists understand the specific challenges of installing precision-fabricated steel units in imperfect historic openings — and how to achieve the required clearances, water management performance, and operational quality without damaging the existing historic fabric.
Begin Your Historic Project Consultation
Historic preservation projects require more upfront consultation than standard new construction — but the result, when done well, is a building that honors its architectural heritage while performing to contemporary standards. HERRERO works with architects, preservation consultants, building owners, and contractors throughout California on historic renovation projects. Contact our team at doors@herrerodoors.com to discuss your specific project, or get a starting-from estimate at quote.herrerodoors.com.
