Thorsen, William R., House
Also known as: Sigma Phi Place
Why it's listed
Set at the corner of Piedmont Avenue and Bancroft Way in Berkeley, this house was designed by the California architects Charles and Henry Greene and dated to 1909 in the nomination. It has an L-shaped plan, dark weathered wood shingle walls, a maroon clinker brick foundation and heavy timbers framing large windows and doors. Long sills and extended rafters give it a sense of elongation. Inside, Burmese teak paneling, oak floors and exposed joinery reflect the architects' craftsmanship. Alterations include an asbestos shingle roof added after the 1923 Berkeley fire, a porch enclosure by Charles Greene in 1927, and bathroom remodeling around 1945. The listing rests on its standing as the only fully developed Greene and Greene bungalow in Northern California and one of six major designs from the height of their careers. It shows how the architects adapted their vocabulary to Berkeley's climate and site, and offers a basis for comparison with their Southern California work.
Significance in brief: The nomination argues it is a fine example of Charles and Henry Greene's work and the only Greene and Greene building in Northern California that shows their fully developed bungalow style. It is one of six major designs from the peak of their careers. Its design and craftsmanship differ from their Southern California houses because it responds to Berkeley's climate, site and client.
Machine-generated summary. This summary was generated by a language model from the official nomination document and has not been reviewed line by line by an editor. It may contain errors. Check the source document before relying on any detail. Source: nomination document (PDF) · National Archives catalog entry. NRHP reference 78000646, listed November 20, 1978. Summary generated October 2026 (model claude-sonnet-5-5, prompt v1.0-2026-10-29, confidence high).
Key facts
| Address | 2307 Piedmont Ave., Berkeley |
|---|---|
| County | Alameda County |
| Listed | November 20, 1978 |
| Reference number | 78000646 |
| Resource type | Building |
| Period of significance | 1900- |
| Architect / builder | Greene & Greene, Architects. |
| Architectural style | Greene and Greene "bungalow style" |
| Areas of significance | Architecture |
| Level of significance | State |
| Status (as stated in the nomination) | Occupied; described as moderately altered and in process of restoration and adaptive use. Owned by an alumni association. |
| Acreage | 0.4 |
| Coordinates | 37.86893, -122.25184 (NPS GIS) |
What listing means for this property
National Register listing is honorary for a privately owned home: it does not by itself restrict what an owner may do with their own money, and it does not require public access. Restrictions come from local landmark or historic-district ordinances, which are separate (how they differ).
Owner-occupied houses are not eligible for the 20% federal rehabilitation tax credit, which applies to income-producing buildings, but many states offer credits for homeowners. Listing also opens the door to preservation easements and to buying a plaque. Start with what listing means for homeowners, renovating a listed house and selling one.
General information, not legal or tax advice. Rules change; confirm with your State Historic Preservation Office or a qualified adviser.
Sources and further reading
- National Park Service, National Register of Historic Places database (snapshot May 2026), reference 78000646.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q7796737
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.