An ornamental iron tree fence provides a barrier to protect trees from hazards such as soil compaction and mechanical damage, which can shorten a tree's lifespan. This specification provides materials, fabrication, and installation method for the ornamental iron tree fence and shall be used by engineers, consultants, and private developers to protect street trees and enhance the streetscape. The ornamental iron tree fence requires a public space construction permit and should be installed by a licensed contractor for DDOT approved streetscape improvement projects.
This work consists of furnishing and installing 18-inch high ornamental iron tree fences with a top row of rings. The ornamental iron tree fence shall meet or exceed the following specifications: ASTM A-787, ASTM A-653, ASTM A-607, as pictured below.
Photo Notes: 3” space between the sidewalk and bottom rail, tree box flush with grade, and the street sign outside of tree box. Ornamental O-rings are optional.
Materials shall meet the following requirements:
- Posts – above grade: 1 inch x 1 inch x 1/8 inch tubing, 18 inches in length
- Posts – below grade: ¾ inch solid steel bars, 18 inches in length
- Top rail embellishment: 1 inch x 1/8 inch flat steel channel
- Top rail: 2 inches molded steel bars
- Mid-rail: 1 inch x ½ inch x 1/8 inch steel channel punched to accept pickets
- Bottom rail: 1 inch x ½ inch x 1/8 inch steel channel punched to accept pickets
- Pickets: ½ inch x ½ inch solid steel bars
- O-Rings: 4 ½ inches tubing
- Finish: all materials are welded and primed with 1 coat of Red Oxide primer and 1 coat of Black Satin paint (Sumter Coating) mixed with primer
Fabrication and Installation
Construction Requirements - Fence shall be 3-sided unless otherwise specified, open side facing the curb:
- Top-to-mid rail spacing – 5.75 inches o.c.
- Mid-to-bottom rail spacing – 8 inches o.c.
- Bottom rail shall sit approx. 3 inches above grade surface
- Post-to-picket spacing – 5.25 inches o.c.
- Picket-to-picket spacing – 5 inches o.c.
- Space O-ring tubing according to picket and post locations; all O-rings shall be welded to adjacent pickets, posts, and rails
- Weld 1 inch x 1 inch x 0.125 inch post tubing at ends and corners and weld an additional post along the length at mid-point. If tree box length exceeds 12 feet, posts should be welded every 4 feet along the length
- To provide below-grade support in concrete, weld ¾ inch solid steel bars to all 1 inch x 0.125 inch post tubing
- To deter seating, weld 1 inch x 0.125 inch flat steel channel to 2 inch top rail
- For existing tree boxes, openings must be measured prior to fabrication to ensure that fences will fit just inside the boxes. The side panels must be fabricated with a minimum setback of 6 inches and 10 inches from back edge of existing standard curb and narrow curb respectively, to allow sufficient room for car doors to swing
- For new tree boxes installations, fence dimensions shall be standardized based on length and width of proposed openings (e.g. 4 feet x 9 feet, 6 feet x 10 feet, etc.), however, the setback for the side panels shall remain consistent at 6 inches and 10 inches from back edge of existing standard curb and narrow curb respectively, to allow sufficient room for car doors to swing
- Use Sonotube forms as per manufacturer’s specifications to set concrete for footings.
- Concrete footings shall be approx. 10 inches wide by 24 inches deep. Concreting shall be performed in accordance with the manufacturer’s specifications.
- Strength: 3000 psi with a slump of 3 inches
- Air entrainment: 5 percent to 8 percent
- Aggregate size: ¾ inch max.
- Mortar compressive strength at 28 days: 4,400 psi
- Meets ASTM C 150, Type 1
- Finished concrete shall be 2 inches below existing grade and pitched to direct water away from posts.
- See DDOT's Standard Drawing 608.13 for details.
- See DDOT Standard Specifications for Highways and Structures 608.06, for specification.