XTEN Architecture is an award-winning international architecture firm based in Los Angeles, California and Sissach, Switzerland specializing in custom residential, cultural and commercial buildings. The full-service firm is led by President and Founding Partner, Monika Haefelfinger and Principal, Scott Utterstrom. Founded in 2000 by Monika and the late Austin Kelly (1966-2015), XTEN approaches architecture with Swiss precision and rigor along with the progressive and experimental spirit of Los Angeles.

Through thoughtful design analysis, our architects distill the parameters of site and project brief into meticulously structured plans that are then developed into distinct sculptural forms. Interior and exterior spaces flow seamlessly, creating a strong connection to the landscape and the buildings’ immediate environment. Our designs are developed using innovative and refined materials implemented at the highest level of craftsmanship; we design with the ideology that advanced structural strategies and sustainable technologies are key in creating buildings for the future.

XTEN Architecture has received numerous architectural awards from American Institute of Architects, the Chicago Athenaeum/ European Centre for Architecture, the National AIA Housing Award, the IV Miami+Design Bienal Architecture Award, the Los Angeles Architecture Award, the Bloomberg Luxury Property Award among others.

The work of XTEN Architecture has been published extensively appearing on the covers of Architectural Record, Architectural Digest, Elle Décor, Architektur & Wohnen and across top-tier media outlets including but not limited The New York Times, Wallpaper, Interior Design, FORM, Interni and AD Mexico. In 2013 work by XTEN Architecture was exhibited in “A New Sculpturalism: Contemporary Architecture from Southern California” at the Museum of Contemporary Art (MOCA) Los Angeles.

Néstor Montenegro. Architect. Partner
Toni Gelabert. Architect. Partner

Team members

Laura Barros
Alfredo García
Paula Maján

Building Engineers

Joan Bonet
Javier González
Javier Mach