Morris Arboretum Tree Adventure / Metcalfe Architecture & Design

© Paul Warchol

Morris Arboretum’s Tree Adventure exhibit Out on a Limb, designed by , was the 2010 AIA Philadelphia Design Excellence Gold Medal Winner, 2010 AIA Pennsylvania Architectural Excellence Award, 2010 “Best of Philly” Award, and the 2010 American Association of Museums Excellence in Exhibition Design Award. Suspended 50 feet above the forest floor this network of walkways (450-feet in length) provides a bird’s eye view of the forest, complete with a giant Bird’s Nest, Squirrel Scramble rope, and many vista platforms.

Follow the break for photographs, drawings, and renderings of Out on a Limb.

Architects: Metcalfe Architecture & Design
Location: Philadelphia, Pennsylvania, USA
Consultant: Forever Young Treehouse, Inc
Structural Engineers: CVM Engineering
Construction Managers: CVM Construction
Civil Engineers: Hunt Engineering Company
Lighting Designers: Grenald Waldron Associates
Exhibit Designers: Sparks Exhibits and Environments
Photographs: Paul Warchol

© Paul Warchol

Tree Adventure takes place throughout the 92-acre Morris Arboretum at the University of Pennsylvania, engaging visitors in the science, history and culture of caring for trees. The centerpiece of the exhibition is Out on a Limb, accessible journey into the treetops.  Metcalfe Architecture & Design used a “play-to-learn” strategy to drive home the Tree Adventure message – we need trees and urban trees need us – and make it resonate with visitors.

From an architectural standpoint, Alan Metcalfe, AIA, LEED AP, firm principal, created places that encourage people to stop, look, turn, move and linger – offering them a chance to “play” with something so familiar yet seen in a new way. Being five stories above the forest floor affords views normally reserved for squirrels, arborists and other tree-dwelling critters.

site plan

Metcalfe Architecture & Design incorporated a high standard of tree and site protection throughout the Out on a Limb exhibit. The structure, made of recyclable metal and wood, does not touch the trees. Rather, it ‘tiptoes’ through the root systems using small foundations called “micro-piles” delicately located amongst the trees.

Off-site pre-fabrication also minimized site (and tree) disturbance. Pieces arrived by truck and were boomed in by a 160-ton crane and bolted to the foundations.


All pieces are independent making the exhibit structurally independent. If a tree falls and destroys part of the deck, the rest of the project will remain safely standing. The lightweight structure can also be relocated and reassembled without totally starting over.

Western Red Cedar, a truly green siding material, was used extensively in the screen surrounding the pavilion. It is 100-percent renewable and sustainably harvested.


The Boardwalk consists of sustainably harvested and locally cut back locust wood decking. This wood is naturally bug and rot resistant, and has been used over the centuries for fence posts. It has gained a new popularity because it is locally available and does not need chemical treatment like pressure treated lumber that has been used over the last 30 years (this could be harmful to little children who are sitting on it).

LED lighting offers lower energy consumption, smaller size, longer life and greater brightness than conventional incandescent lighting.

Cite: Minner, Kelly. "Morris Arboretum Tree Adventure / Metcalfe Architecture & Design" 14 Dec 2010. ArchDaily. Accessed 24 May 2015. <>
  • Holcim Awards

    Wow, what a wonderful and playful piece of architecture. This is a perfect integration with the surrounding context and a fun way to get people to interact with both architecture and trees. This should be submitted to The Holcim Awards for Sustainable Construction: