Ferrocement Photo Gallery

Ferrocement Photos

Ted Baumgart's Curved & Cantilevered Stairway


29 files, last one added on Feb 01, 2005
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Random files - Ted's Gallery
Photo 211315 viewsPictured from the left is myself and my son Dan. We have just completed thelast step. In work sequence I chose to mud the bottom step first, then startfrom the top and work down, because the bottom step appeared most forgivingfor the learning curve. We were using untried PVA rec15 fibers in our mix,pushing this through layers of 1/4" woven wire steel mesh, a potentialnightmare. The lowest step is the easiest to reach, rests firmly on anon-flexing concrete foundation, is small in volume, and has a minimum ofunderside to hand finish. The other four are flexible, larger, and have alot of underside to finish. To begin with I wanted the best chance to adjustour mix and application methods, and clock the application time beforetackling the more critical stair steps.
Photo 191060 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 241287 viewsLook for the pasty yellow looking thing under the step, that's my armworking from below. I spent more time below than above because there wasmore surface area to finish, and it wasn't flat work, but rather on-my-backconvex and curvilinear finished surfaces. Did I mention that each step tookhalf a day to mud, including cleanup? If this were sprayed into a mold itwould have been a half hour.
Photo 291609 viewsThe goal was to create a simple, modern, and clean looking stairway. Curved and cantilevered, floating effortlessly, goal achieved.
Photo 081010 viewsAfter lifting off the wooden mockup as a unit and putting it aside, we are now looking at the steel armature that appears more interesting than the final product might. This is like looking at a painting being made and noticing that the painter's pallet looks better. I could walk away now exclaiming "Eureka, this baby's done!", but it wouldn't function as a stairway. I saved the particle board templates created as guides used for plasma cutting the steel brackets to exacting dimensions. The squiggles on the top edges were designed to increase the mechanical interface between the steel plate and the FC treads yet to be built. I didn't want to create a straight parting line where forces might accumulate and form a crack. A good marriage has many ties. Posing oddly with sledge hammer and screw gun is one of the best structural welders I've met, Mario Perez. He took knowledge of metallurgy to the molecular level, careful not to weld completely around the pipe, and mainly on one side of each bracket. The mark of experienced structural welders is not how much weld metal they throw into the work, but how little, the weld being the weakest part. He didn't want to generate cracks, or warp things in the process. This is seen in the photo of the sandblasted frame. Notice that the brackets encircle the pipe to physically grab the entire circumference like a strap, transferring the loading all around the pipe. The brackets will work as true torsion arms when you step on the stair treads cantilevered off of the pipe's side. But why is Mario holding a sledge and screw gun? "If it doesn't go in one way, it's going in another. You try screwing into 1/2" plate." We joke.
Photo 10992 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 091149 viewsI liked the frame with the rust on it before sandblasting. Next step is powder coating. The client wanted it a gray cement color. This is a project about projecting modern clean lines, restraint, and simplicity through illusion, smoke, and mirrors. We are making magic.
Photo 15993 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.

Last additions - Ted's Gallery
Photo 291609 viewsThe goal was to create a simple, modern, and clean looking stairway. Curved and cantilevered, floating effortlessly, goal achieved.Feb 01, 2005
Photo 281580 viewsThe stairway is complete but it's good to keep a perspective. It's just another day in the life with Willie, and Willie knows what's important.Feb 01, 2005
Photo 261370 viewsDoes this look like bliss or purgatory? I was singing and soaring withnature's forces.Feb 01, 2005
Photo 271699 viewsBelow is the mix low down, and above is another view of work in progress. After completion I wet cured the steps for a full 30 days before use. A temporary ramp with barriers protected the steps from all use. The steps were covered with plastic sheet and plywood mockup cutouts. The work was also tented tightly in 6 mil plastic sheet with 2 large shallow water filled plastic cement mixing tubs placed inside to keep the air humidity high for 30 days. The weather was Southern California December, 52-60 degrees F shaded from sunlight by the house eves and surrounding trees for great slow sets and a long, strong cure.ECC MIX MATERIALS:
1) Graded feldspar silica blasting sand, bagged and dry mixed in nearly equal portions by weight: #16, # 20, #30, #60, #90, #120 grit
2) Portland cement, low alkali, type II/V
3) 100% Acryl 60 (no water)
4) PVA (Poly Vinyl Alcohol) REC15 fibers 1/4" grid woven wire steel mesh (M/Steel, 4 X 4, 1.190 wire, roll 36"W x 111'L)MIX RATIOS BY WEIGHT:
The first batch was weighed with a scale in ounces, each separate ingredient placed on the scale in plastic Straus brand yogurt containers: 317 oz sand (combined weights), 60 oz cement, 4 to 7 oz PVA fibers (under 2% by weight), 19 oz Acryl 60 or more but kept to the bare minimum possible except in the batches being pushed into the interior of the space frames.
MIX RATIOS BY VOLUME: The weights chosen closely resemble the volume ratio of 1:3 cement/sand.MIX TOOLS:
A) Milwaukee heavy duty 1/2" angle drive drill, 4.5 amps, 0-500 rpm
B) Onebone style mixer, homemade, metal blades on all-thread
C) 5 gallon plastic buckets, half filledMIX METHOD:
The dry mix was given a short stir with the Onebone mixer, the liquid was immediately added, and all mixed for 30 to 60 seconds at 150 to 300 RPM.SET CONTROL:
Cool days and the Acyrl 60 gave us an hour to apply each batch of mix as long as it was spread out and not massed in any container where chemical reaction heat could accelerate the set. (Each stair step took 4 to 6 buckets half filled.)BUBBLES: Slow rising air bubbles were a problem if the surface was float-troweled too long. The Acryl 60 did not let bubbles rise and dissipate easily. Various vibration techniques were briefly tried but not liked. Short slow power mixing, the no-air-encapsulation mud application technique previously mentioned, and a quick and efficient trowel finish on the top were the answers to bubble potential. "Johnny, don't play with your potatoes!"
Feb 01, 2005
Photo 241287 viewsLook for the pasty yellow looking thing under the step, that's my armworking from below. I spent more time below than above because there wasmore surface area to finish, and it wasn't flat work, but rather on-my-backconvex and curvilinear finished surfaces. Did I mention that each step tookhalf a day to mud, including cleanup? If this were sprayed into a mold itwould have been a half hour.Feb 01, 2005
Photo 251176 viewsThe most spiritual part of the job was in smoothing out the convex cuppedlooking areas underneath each step, largely hidden from view. Because of thelittle rod trusses previously mentioned, each step had regularly spacedbumps under them to deal with. They created little convexities between them.I grabbed the smooth Mexican beach pebbles you see as shaping and smoothingtools. I quickly began hearing surf sounds in my head, while slurping andsliding, and gliding the smooth rock over wet mud. An occasional spritzingwith the water spray bottle lubed the process. I began connecting sculpturalshaping with nature's forces, feeling like a magnetism was pushing my hand.I also realized I had been under the steps too long and had a long way togo. Go with the flow I say. I began singing.Feb 01, 2005
Photo 231359 viewsHere's the nitty gritty. This was the biggest bear to fight, getting the mudinto the mesh without voids. On a hunch I stopped by the local OSH hardwarestore and purchased toilet plungers to force the ECC mud. ...Any trick inthe book and then some. While holding four of them in my arms in theshopping isle, the guy next to me commented on the plumbing problem I musthave. He was a concrete engineer and we talked for an hour. He approved ofmy 'manual hydraulic mortar emplacement tool'. I'll explain how one must'roll' the mud into place to avoid voids. I learned it decades ago in dentallab on the plaster bench. Like a slow motion tsunami wave you push orvibrate the wet material outward directionally, never gulping air, neverencapsulating air or creating bubbles. You watch the leading edge of your'wave' as it consumes everything in it's path in slow-mo. Doing this with atoilet plunger was a new wrinkle. The 3 sizes of trowels were helpful butcouldn't generate the pressure needed to get the mud thoroughly through thewire mesh and protruding out below, like a meat grinder making hamburger. Weare talking about very physical work here. Given the time constraints ofinitial set, we really put our weight into the job. When satisfied withpenetration we then plopped on a mound of mud and spread it out on top,level with the aluminum angle forms. Last I floated a smooth finish andcrawled under the step to begin smoothing out the bottom. We are talking areal hump job here, given the time constraints of the setting ECC mortar. Ithelps that we had three of us, one continually mixing small batches, and twoothers schmushing and finishing. Also the days were cool, slowing the set.Feb 01, 2005
Photo 221303 viewsTalk about getting 'at one' with the work, I'm 'into it'. Notice thealuminum angle as edge forms for crisp corners. You can get away with lessprecision if you somehow strike clean edge lines on your work. The angle iswaxed and then tie-wired in place to the mesh, to be removed after ECCplacement and cure. Notice how they hang loose until packed with ECC. That'sto give the precise space for the ECC to cover the mesh. You can see plasticsheeting under the plywood, it's covering the exposed mesh to slow therusting in the rains we had been having. I used that plastic later to coverour newly troweled ECC steps too. I didn't want plywood to sit on the curingECC sucking moisture. The pipe plug is protecting the threaded stainlesscoupling inside the ECC. That coupling is the means of attachment for ahandrail should one be desired. The clamps are holding more aluminum angleserving as crisp forms where mud will meet the steel plate brackets.Feb 01, 2005