Ferrocement Photo Gallery

Ferrocement Photos

Photo 011210 viewsThis particular little stair design is about a marriage of 1/2" steel plate and 8" diameter pipe to ferro cement treads in a live loading situation. There are easier choices in materials and methods for this situation but I wanted to test this combination out of curiosity regarding future projects. As people walk on these stairs the loading of the cantilevers asks the materials including the mechanical joint between steel plate and ferro cement to perform reliably in tension, compression, and for extra fun, torque. I didn't create molds for this job because this is a 'one off' project and each stair step is shaped differently. Using molds in a slightly different application would have been the better way to go for efficiency, labor savings, structural quality, and surface treatment. In the past I've cast metal structural frames into molds in a variety of venues from partial acrylic/ dentures and crowns/bridges in dental lab prosthesis to hidden epoxy 'belly boards' for 'flying' Superman patrons (hydraulically) at Universal Studios. These are similarly continuous live loaded appliances using metal frames molded into a plastic medium. This particular ferro cement stairway project proved to be intense in labor, but 5 molds would have been another major fabrication step for a stairway made exclusively for one site. I will reserve molding FC onto metal for similar but far larger projects. Anyway, I wanted to re-experience the pain and agony of wiring mesh, pushing mud into it, this time with PVA fibers in the mix.
Photo 10991 viewsI applied special heat tape to mask off the powder coated paint from covering areas to be in direct contact with the ferro cement. I pondered this decision. You want the cleanest, most direct contact between all metal and the cementitious material. This is for reasons of adhesion, and to not introduce materials with different expansion and contraction heat coefficients that would work the materials apart (cement and steel being beautifully similar). But in this situation we will have a metal frame that is not completely encapsulated by mortar, leaving a potential gray area (pardon the pun) open to the intrusion of wicking moisture up into the uncoated metal. The metal would then expand with rust, and crack the mortar eventually leading to disintegration of the structure's integrity. Solution? I masked so that paint areas would be covered about an inch with 100% Acryl 60 mixed mortar, a compromise strategy. This situation is downward facing, and would be sheltered deeply under each tread. I also later shaped the mortar so condensate is encouraged to fall from the cement before running down onto the painted metal plate surfaces. I would never risk this design in a wet geographical climate because of wicking upward potential. Also, just prior to mortaring I sprayed a coat of rust converter onto this 'gray area' to stabilize any metal oxides present. What else for a potential Achilles heel? If this becomes a problem down the road, we'll all be gone to 'ferro cement heaven' and the house itself will be remodeled. I give this FC/steel interface area of the project 100 years before trouble, and the vacillatudes of fashion will do this work in faster than any other force on the planet.
Photo 11937 viewsFinally at the site, the awkward 'beast frame' took six guys to lift off the truck, carry down a long narrow walkway, through several gates, down some steps, to carefully nudge and block into the correct position. After I welded structural steel angle at both ends of the frame (you can see some protruding out of concrete), I built forms in the soil and poured concrete footings, encapsulating the frame at both ends. Although the two footings are resting on their own soil independent of the house foundations, I also drilled and pinned with rebar the one under the porch to the existing foundations before pouring. Once the concrete set I also bolted the hidden metal frame at the top of the stairs to the porch joists underneath, running straps back to the third joist, blocking them in between with wood. Anticipating earthquakes, everything is massively tied together in concert. If the frame started moving at odds with the house, it would mash the house. We guessed the metal frame weighs 450 to 500 lbs without it's concrete footings. She was an awkward curvy shape to carry in and here she finally has found her resting place. Note the lower foundation in the foreground. This is where that plate visible in earlier photos has been encapsulated along with scrap angle and rebar. The visible rebar pins sticking up are for attaching the lowest step tread which will hide this footing.
Photo 12879 viewsAn illustration can be superior to a photograph by focusing on the topic and excluding everything else. In this illustration all foundation work will be hidden, particularly the steel angle frame emanating from beyond the upper step. This will be hidden under the porch, and the foreground foundation hidden under the bottom step. The entire unit is self supporting and braced against movement in all directions. The 8" schedule 40 pipe is not overkill. A lighter pipe would have necessitated a foundation that connects the two foundation 'feet'. The prop company had this pipe on hand as leftover from a job and donated it to the cause.
Photo 13932 viewsTo begin rod work, I took the full sized plywood step treads from the shop mockup and cut and welded my 3/16" cold roll steel rod on each plywood step. I compensated for the thickness of the future mesh and mortar by bringing in the rod work about 1/2" all around. I kept handy my little garden spray bottle filled with H2O to put out the wood fires as I welded the rod laying directly on the plywood. After welding in triangulation rods to stiffen the work, I took the new 5 metal steps-to-be to the site, ready to weld onto the armature, just as you see in the lower illustration. The widest step is about 8'/4" long.
Photo 14963 viewsUsing a level and tape measure I carefully tack welded each step to each bracket with little vertical pieces of 3/16th, being careful to get each step leveled left to right, tilted forward 1/4" in 12" (for water runoff), and exactly 7-1/2" above one another. I also filled rod in under the ends of each. I can still stick weld rod faster than Benihana can chop meat at your table, but this work had to be exact.
Photo 15991 viewsAfter completing this I went back and rewelded each connection nice and tight. That took me a day. Why so much rod? This assembly will serve immediately as a functional temporary stair using the same mockup plywood now wired on top as treads. This gives everybody a break. At the house there is an ongoing remodel with contactors, not to mention the family and pets who live there. In this in-between state of being the rod must not warp or move. Notice the little rod trusses under each step to give support out to the edges. Underneath that are long horizontal rods pegged out from the 1/2" plate brackets for attaching the wire mesh. Now we are ready for mesh. Walking on these at this point tested their sea-worthiness. To dampen all vibration I additionally welded one hidden, short piece of 1/2" cold roll steel rod to the back of each step, connecting it to the huge pipe directly below it. This amounted to 'tripoding' each tread to the pipe dampening vibration in two axis. Wondering what the smaller pipe is protruding left under the bottom step? It's a hefty steel pipe, 1" diameter/ 3/8" wall, acting as a torsion arm attachment for a hand railing. I used a stainless threaded schedule 40 1" pipe coupling at it's end that set flush with the final FC/ECC mortared tread surface.
Photo 161028 views1/4" grid woven wire steel mesh is tie wired to all surfaces, including mesh strips down inside the rod work stretching from tread front to tread back, and mesh layers on the inside of all rod work, tightly encapsulating sandwich-like all the rod, two sides. This operation took two men almost 4 days to do my way. As far as labor goes, I really like gun spraying GFRC (glass fiber reinforced cement) into molds. Yet the woven wire mesh system with the thin rod inside will be stronger in this application. Extra insurance on stairways is a good thing in my book.
Photo 17914 viewsHere's a closer view of mesh on rod. It was nice to sit on the plywood covers below the work at hand. I spent years in the Rose Parade Biz welding rod or attaching wire to rod up in the air with little to stand on but more wanky rod.
Photo 181099 viewsFunctional yet temporary, the plywood covered mesh steps languished in this state of incompleteness longer than I care to admit. They functioned well however, and didn't deform or move at all.
Photo 191055 viewsThe rod was there longer than the mesh as this closer view reveals rust on the rod but not so much on the mesh. Although not really needed, we wire brushed everything in case there was loose rust or scale. We then sprayed a thin coat of rust converter on the few heavier rusted areas. We are now ready for mud.
Photo 02974 viewsThese plans are the 'first pass' at design within the site's dimensions. You can see that I was going to make metal tread trays and simply fill them with a cement material. But why do it the easy way, I wanted to save tread weight and play with ferro cement. When complete the treads minus their steal plate weighed an average of 84 lbs. each, but could hold 2000 lbs. I figured a gathering of friends for a photograph on these stairs could load a tread 1000 pounds. Add jumping up and down, and a pet elephant...
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