Tejon Addition

Project Overview

Location: Colorado Springs, Colorado Architect: Compass | TDG Architecture Type: Residential Addition, Existing Building Interface

This project involved a substantial addition to a Victorian-era multi-story residence in Colorado Springs: increasing the home’s square footage by approximately 50% through a full-height addition with a new basement and a full-width covered porch spanning the rear of the structure.

The architectural vision required the new construction to feel integrated with the original home both aesthetically and structurally. That integration created the project’s central engineering challenge: how to connect a new modern basement to an existing mass stone foundation without compromising either system.

Existing Foundation Interface

The original home was built on a mass stone foundation typical of late 19th and early 20th century Colorado construction: a rubble and coursed stone bearing wall with lime mortar, significant mass, and zero engineered reinforcing. These foundations perform well in pure compression but have limited capacity for the lateral and overturning forces that accompany large additions.

At the new building interface, Frontier designed a new basement wall sister connection: a reinforced concrete wall built directly against the face of the existing stone foundation to share and redistribute the bearing and overturning loads generated by the addition. The sister wall was designed to engage the existing stone passively in compression while taking the net overturning demand through its own reinforced section and new footing.

The high overturning load condition at this interface (driven by the full-height addition bearing down and the porch roof spanning out) required careful load tracing to confirm that the combined system remained stable under all lateral and gravity load combinations without overstressing the original stone.

Covered Porch and Addition Framing

The full-width covered porch at the rear of the addition required a long clear-span beam to avoid columns in the middle of the porch deck. The beam bears on new posts integrated with the addition framing and transfers load cleanly to the new foundation without engaging the original structure.

The addition’s floor and roof framing was coordinated with the architect to match the existing floor elevations and roof pitch, ensuring the two structures read as one from both inside and out.

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