top of page

owner/ lead designer


Mary "Allison" Prehn Henson


             aving grown up in Fredericksburg, Allison is glad to be back “home”. A favorite piece of her six-generation-heritage in the Texas Hill Country is her family’s peach orchard that she helped operate as a kid.

"It both grounded and equipped me with skills required later in life.”

     After graduating from Texas A&M with a degree in Environmental Design and minor in Business, she landed a job with the top-ranked architecture firm HKS, in Dallas. It was there that she worked alongside world-class professionals and clients and advanced quickly from working in the role of “Intern” to managing large projects and teams. After a stint in HKS’ hospitality department, she moved to the healthcare sector, taking on various roles related to the design and construction of hospitals across the United States.

     “My dear friend in architecture school lived with a lifelong debilitating disease. A close view into her world profoundly influenced my career choices - understanding that while I could not alleviate she and her family’s pain, what I could do was help create spaces that could make people in similar positions more comfortable, both functionally and aesthetically. My own experiences with medical facilities only then highlighted my understanding of the profound impact those spaces can have on us - for better or worse.”

     While Allison was designing in a corporate world by day, her personal time consisted of "dressing" homes - for herself, family and friends. Whether it was shopping for antiques, arranging flowers, selecting paint colors or fabricating handmade pillows, her creative mind rarely rested.

     This made for a smooth shifting of gears in working from the other part of her heart - homes. While raising her young son she performed contract work for a residential architect, and then when it was time to move “home” to Fredericksburg, residential interior design was the logical next step. “I was so fortunate to get to work professionally doing something I loved to do in my spare time... and learned so much in the process.”

     She is now combining the various pieces of all her experience to form Mary Allison Designs, where thoughtful design will drive a seamless transition between a project’s exterior and interior. 

HKS                                                 Dallas, Texas

   Ireland Army Community Hospital   
Fort Knox, Kentucky   :::   550,000 sf
  Project Architect
(acting role/ non-licensed)  

   Benjamin Russell Hospital for Children Birmingham, Alabama   :::   760,000 sf
  Medical Equipment Coordinator, Junior Construction Administrator

   Texas Health Presbyterian Hospital
Flower Mound, Texas   :::   180,000 sf
  Junior Project Architect, Junior Planner, Job Captain 

   Charles E. Schmidt Medical Center   
Boca Raton, Florida   :::   1,000,000 sf
  Junior Planner, Job Captain

   The Cove at the Atlantis Resort
Paradise Island, Bahamas  
  Intern Architect

Olsen is now Demesne:
  contract work as: Architectural Designer, Drawing Coordinator, Project Documenter

   Interior Designer / High-end Residential
  work included:  interior finish + fixture selections • exterior finish + fixture selections • space planning • collaboration with clients, architects, contractors, vendors • furnishing selections: custom, antique, ready-made • design + construction drawings • furnishing installations


Olsen Studios                                    Dallas, Texas

Slaughter Design Studio         Fredericksburg, Texas

bottom of page