Introduction: Pipe Trellis
This project is part of a much larger one that I assisted with for the past year. My wife is a member of the Penn State Lycoming County Master Gardeners and was the chair of the committee to build a Sensory Garden in Montoursville, PA. Through her involvement, I ended up helping with many facets of the project. When the group asked me to review some preliminary quotes they had received for materials I volunteered to head up the project.
Step 1: Design & Planning
I was provided with a picture of a similar structure as a starting point. From there I used my favorite program; Trimble SketchUp Pro© and commenced the design of the project with input from my wife. After a number of iterations using various dimensions, materials, and styles a concept design using copper pipe was completed and approved by the committee. After this came the budgetary concerns. Various configurations of the structure were designed and estimated using different fittings and fastening combinations to reduce the cost without reducing the strength or utility of the assembly.
Once the final design was complete, I shopped around for prices and ended up using a number of vendors to get the most competitive prices for the requisite materials.
Step 2: Materials & Tools
Since the materials & tools lists are quite extensive, I have provided them in a pdf file format to view separately.
Step 3: Excavation & Concrete
There was some difficulty finding a place that could bend the Type L copper to the designed configurations. Type L copper has a thicker wall than Type M which is used in normal residential plumbing. Because of the greater wall thickness, it can withstand greater pressure and is used for underground piping and in commercial applications. Though no internal pressure would be put on the pipe, the greater wall thickness makes it more rigid, which was desirable for this project. This same rigidity makes it difficult to bend without kinking. Ironically, after a couple weeks of searching, a company was found that could perform the work located only a half mile from my house.
During the search time the bulk of the copper (pipe & fittings) had been delivered and I had gone to the other vendors and collected the remaining fittings and materials.
While waiting for the arches and curves the holes were excavated and concrete was placed for the supporting legs. The structure connects the new Sensory Garden to the existing Demonstration Garden and once its extents were determined and marked with paint, stakes were placed with string lines to indicate the two parallel sides of the structure. Along these lines, measurements were taken and marks were made indicating where the center of each Sonotube© concrete form would be located. When the marking was completed I had assistance from students from the Penn College Construction Management (BCM) program in Williamsport, PA to perform the strenuous part of the project.
The students used an Easy Auger© with 8” and 12” bits to drill the holes for the Sonotube forms. The ground was very hard and rocky which necessitated the use of an electric jackhammer and pry bars to excavate to the proper depth. The horizontal position of the forms was maintained using the original lines and the elevation was held by measuring from the line to the bottom of the holes. Once the proper depth was attained the elevations were checked with a transit. The forms were cut to length, set in place, and soil was backfilled around to hold them in place.
When the forms were secure the concrete was mixed using an electric mixer and poured using buckets and a wheelbarrow. The project was then barricaded and members of the Master Gardeners took turns keeping the concrete moist for a few days.
Step 4: Finials
While the concrete was allowed to set, work was done on the finials that form the tops of the handrail sections. The finials consisted of a 1.25" copper cap, 2" brass ball, brass finish washer, threaded brass rod, and brass nut.
The 2” brass balls were hollow and had a hole in them when purchased. The holes varied in size, so each was drilled out with a 13/16” drill bit and then threaded with a 1/4" – 20 tap. The same drilling and tapping was done to the 1.25” copper caps. A 3’ threaded brass rod was cut into 16 - 2” lengths and each was threaded approximately 1/2" into a brass ball. At this point the threaded rod was soldered to the ball. A brass finish washer was placed on the rod and then the cap was threaded along with a nut. The cap and nut were tightened and then the rod was soldered again. This was done in an attempt to stop someone from just twisting off the brass balls and taking them.
One of the major irritants on this project was removing all the stickers and shipping adhesive from each piece of the project. This was accomplished using a two adhesive removing products and scraping with a plastic putty knife.
Step 5: Layout
The next step on site was to set up batter boards so that proper layout and positioning of the flanges could be done. Each galvanized flange had a 1.25" male thread-female fitting attached and was positioned on the 8” diameter concrete footings (one for each of the twelve main supports). The flanges were positioned in their proper places and the mounting holes were marked on the concrete and anchoring holes were drilled using a 3/16” masonry bit. Some of the forms had moved slightly during the pour, so the concrete was ground off using a right-angle drill and concrete grinding bit to level out the surface. The remaining imperfections were dealt with using a bullseye level to plumb up the fittings. One quarter inchgalvanized washers were utilized to shim up the flanges and Tapcon© screws were used to fasten them to the concrete.
Because the tops of the concrete footings had some variance in height, it was necessary to attain the elevation of each, so that the lengths of the legs could be cut to ensure the structure would be level. A transit, tripod, and leveling rod were used, as well as assistance from my lovely helper.
Step 6: Erection & Bracing
Erection of the project started with cutting each vertical leg to a rough length and soldering a union to one end. I used the elevations shot in the previous step to adjust each of the legs for length. Each of the twelve legs were set in one of the male thread-female fitting without soldering. At this point I decided to put the arches in place on the ground instead of after the legs were soldered in place. This was done because the copper came from the suppliers with some imperfections in the straightness and the parts that were bent for the project had variances. This would have made it extremely difficult to match up the legs and ends of the arches while standing on a step ladder. I was also able to perform the assembly by myself on the ground, while doing it after would require two people on ladders.
After installing the vertical members, the entire assembly was braced to keep each part in position. This was done with 2x4s and galvanized strapping material that went around the parts and were screwed into the wood. After everything was plumbed and leveled, the vertical members were soldered to the flange assemblies.
Step 7: Horizontals & Fastening
Next were the 1.25” horizontals that ran the length of the main section. There was one at 2’-0” above the top of concrete and a second at 4’-0” above it. These horizontals tie into the handrail sections as will be seen in the next section. As mentioned previously, it was determined that these pieces would be mechanically fastened to avoid the number of copper fittings. Therefore, holes were drilled through each leg and the horizontal and 1/4" brass machine screws, finish washers, and nuts were installed at each intersection.
After the horizontals were installed, work commenced on the arches. The 1/2" lengths of copper pipe were installed at approximate 20 degree increments around the arch. To make this manageable for one person, I used wire ties and a wire tie twister to temporarily hold the lengths in place while they were drilled and bolted. Note: A wire tie twister is normally used to hold reinforcing in place for concrete work.
After the mechanical fastening was complete, the ends of the pipes were cut off at a uniform length and 1/2" caps were installed and soldered in place. The remaining soldering of the main structure was also completed at this time.
Step 8: Handrails
The position for the handrail flanges were located on the 18” concrete footings using the original layout lines. The same procedure previously described in Step 5 was implemented to level and anchor all sixteen flanges. Once they were in place the vertical members were placed and adjusted accordingly using levels and clamps. All of the members were cut to length and fit in place prior to soldering. After everything was checked for plumb, level, and square, each handrail unit was disassembled, cleaned, sanded, had flux applied, and reassembled. Everything was then soldered starting at the bottom and working up. A ratchet strap was used to hold things secure and square when needed during this process.
Step 9: Completion
The final step was to clean the pipe and fittings. The entire structure was wiped down with acetone to remove excess flux and any remaining shipping adhesive. It was wiped with a cotton cloth and Tarn-X©. This provided a uniform, shiny appearance for the grand opening of the Sensory Garden the next day.
Note: I saw the trellis just shy of two weeks from the grand opening and was surprised how much it had tarnished during this time. The color will change to somewhere between brown and black in the future and should eventually acquire a green patina through oxidation. A picture is provided for a comparison.
Step 10: Sensory Garden
It's not part of the project, however, I have provided pictures of the Sensory Garden for those who might be interested. It is a wonderful area for people with disabilities, the elderly, children, and all others to come and experience nature with all of their senses.
Second Prize in the
Outdoor Structures Contest