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- a new construction technique

using nylon fishnet and cement


Bill Birdsall



     Around 1975, the adventure began. I purchased some undeveloped land on a mountaintop in Puerto Rico and began to make it my home. It was a beautiful area, with a panoramic view of mountains and valleys covered with lush green tropical forest. On one side, about a tenth of a mile away, the paved road ended, and my nearest neighbors, mostly coffee farmers, lived. On the other side were hundreds of acres of forest extending to the river below.


    For various reasons, there was no access road to the building site in those days, and I often had to haul in materials by hand from up to a tenth of a mile away. To meet my immediate shelter needs, the first structure up was a one-room, 12 X 16 ft. plywood cabin, raised about 3 1/2 ft. off the ground on cast concrete posts. Design-wise, its major features were a sleeping loft to leave more floor space open, and plywood windows that pivoted up and were held open by prop sticks, creating a shade awning effect when open, and a secure closure when down and locked by heavy pins.


    Although I now have public water, electricity, and telephone service, for my first eight years I had only water. Light was provided by gas lights, kerosene lanterns and candles. Regular telephones did not appear in our barrio until about five years ago. Until then, there was only a radiotelephone at the "colmado" (small general store) a couple miles away.


     For those first eight years, I dedicated my time mostly to practicing various fine arts, such as painting and sculpture, and clearing some of the forest to plant a variety of fruit and nut trees. Since trees take so long to produce, I wanted to get them in right away.


     Fortunately, due mostly to distance from society, I was able to operate in a way that might not be tolerated in a major city. Basically, I was able to develop my ideas spontaneously, testing experimental and alternative ways of doing things. My home grew organically, based on general principles, but no rigid building plan. Learning through experience, my success rate with experiments improved over time.


    I had several general ideas that I was working with. For one thing, due to it being the tropics, there are some problems with wood, such as termites, "polillas" (like invisible termites), and wood rot. To some extent, those problems are avoided these days by using treated wood, but when I began my building there wasn't much of that, and the material most people preferred was cement.


    Standard cement construction in Puerto Rico consists of a massive foundation, with heavy cement block walls, and a cast cement slab roof. This involves a lot of material, and due to the distance factor, hauling that much material in on my back was not a very enticing idea. Also, due to the weight of the structure, any foundation slippage can cause serious cracks in the heavy walls. Furthermore, the low cement slab roofs tend to absorb a lot of heat during the day and radiate it down at night, making the environment for sleeping less than ideal.


     Due to the distance factor and the need to transport materials in by hand, one of my guiding principles was to do the most I could with the least amount of material; to look for thin shell solutions wherever possible. Also, I had been influenced years before by the concepts of geodesic domes, and ferro-cement boat building. Geodesic domes tend to leak, though, due to expansion problems at their joints. About the only kind of domes that didn't have major leak problems were cement domes.


     Domes also have the advantage of giving the maximum amount of internal volume, with the minimum of surface area material. I also liked the high ceilings in domes, something which would help keep rooms cooler in the tropics, given a heat escape opening at top. The spaciousness of domes felt comfortable to me, and as studio workspace goes, it would allow me to work on big projects indoors, if the doors were big enough to get things out.


    The complex curvature of domes also gives them a lot of strength that the same amount of material in a flat configuration would not have. Think of how difficult it is to crush an egg between your hands, and how easy it is to snap a cracker. In hurricanes, also, a dome shape tends to part the wind, whereas a flat wall would act as a sail. Also, domes have no roof overhangs for hurricane winds to grab hold of.


     While all of these background ideas were gestating over the years, several of our hurricane seasons, and a few close calls had come and gone. Although my plywood cabin was solidly built, I felt that my safety would be best served by making a hurricane shelter. The opportunity to try my hand at ferro-cement construction, and maybe a sample dome structure attracted me, so I began what was eventually to become my adventure with nylon-cement.


* The Hurricane Shelter:


   Floor areas in my home were all excavated by hand using a pick, "coa" digging bar, hoe, shovel, and wheelbarrow to dump the earth off to the side, and to extend the patio areas. From the door of my cabin, looking up the ridge to the south, I began to visualize the shelter being half-submerged into the earth, and a large patio area between the cabin and the shelter. After a lot of "good exercise", that came to pass.


     Ferro-cement means iron and cement. Ferro-cement boat construction is done by making the inverted boat shape as a basket-like grid of iron rods, tie wired together at their intersections, and covered with three layers of chicken wire to hold plastering with cement. After plastering inside and out with a 3:1 ratio of sand and cement (with a little lime added for extra hardness), the walls are about 1 1/2 inch thick.


     At the time I made my hurricane shelter, I was not yet thinking of using nylon fishnet as a substitute for chicken wire in cement construction, so the dome roof of the shelter was done with standard ferro-cement techniques. The carved earth areas, though, were shaped somewhat like rocks, and I liked their natural appearance. Chicken wire, in close proximity to the ground, would probably have rust problems over time, and as iron rusts it expands and damages the cement. Furthermore, chicken wire is not very flexible. To get it imbedded in the cement, the cement layer would end up being fairly thick, and the rocky contours I was hoping to preserve would be lost.


    The solution to the problem finally came to me when I remembered the nylon fishnet catalog I had mailed away for, suggested by one of the "Final", "Last", "Ultimate" Whole Earth Catalogs. If the nylon mesh material could be substituted for the iron mesh material, then the rust problem would be avoided. Furthermore, the fishnet should be much more flexible than chicken wire, allowing for a thinner layer of cement, and a closer following of the contours of the carved earth. If the cement did crack, the nylon fibers would hold the pieces in place; and at the same time, the cement would protect the nylon from harmful ultraviolet sunlight radiation. Thus was born the concept of nylon-cement. I tried it, and it worked.


* A World of Possibilities:

     OK, things start getting a little bizarre now. This was exciting! I had what was, as far as I knew, an original material combination, and I was eager to explore all of its potential uses. I began envisioning projects above, on, and below ground level.


     Due to the flexibility of the material, there were no limitations as to form; something that attracted me no end as an artist. Any shape I could carve into the earth, I could preserve with about a 1/4 inch thick layer of nylon-cement. That could include floors, stairs, outdoor furniture, ponds, septic tanks, walkways, retaining walls, and who knew what else?


     Above ground, so long as the fishnet could be supported until the cement hardened, any form was also possible. Growing out of ferro-cement technology, the first support material that came to mind was iron rods, which is what I used to make the above-ground portion of my house. In recent years, I have also been stretching the netting out like a tent over pole supports, and then removing the poles after the cement hardens. This has an advantage in that it completely avoids any future problem with iron rods rusting and damaging the cement.


     I have always loved caves, and so thinking of taking nylon-cement underground, and making tunnels was a natural evolution of its potential for me. I began to visualize digging something like a deep well between the plywood cabin and the hurricane shelter, horizontal tunnels leading to a hillside entrance, and then a big dome room which would unite the cabin, the hurricane shelter, and cover the opening to the vertical shaft.


* The Vertical Shaft:


     In order to have good lighting for digging the vertical shaft, I decided to postpone making the roof of the main dome room until the shaft was completed.


     The next problem was how to dig the shaft, since I was living and working alone. The horizontal tunnel I was imagining would eventually pass underneath the plywood cabin. In order to feel secure that the whole thing would not just collapse, I eventually ended up going down 30 ft. from the floor of the main room to the floor of the tunnel, before starting to dig sideways.


     Although with the nylon-cement, I could make a perfectly cylindrical shaft, I decided, mostly for esthetic reasons, to carve the dirt like rock boulders. This would also give me the advantage of being able to rock climb the walls in order to get up and down, instead of having to work around a ladder. This solution ended up working very well.


     The problem of how to raise the dirt I dug, and how to dump it off to the side of the shaft was solved in an inventive sort of way that smacks of Rube Goldberg. Basically, I welded up two vertical pipes and a horizontal pipe that passed over the shaft, connected to the tops of both poles. Pulleys were attached to the horizontal pipe. An arm that hinged on one of the vertical pipes, and was controlled by ropes dangling down into the shaft from the pulleys, had a hook and releasing mechanism for holding a bucket on a rope. From the bottom of the shaft, using only ropes, I could hoist buckets of dirt, have them hook onto the arm, swing to the side of the hole, dump the dirt behind a barrier, return over the shaft, disengage, and return to the bottom of the shaft for more dirt. The bucket could also be used for sending down loads of cement for plastering the walls.


      For safety's sake, I dug the shaft in sections, about 5 ft. at a time. After plastering one section, I would dig the next, and plaster it leaving some overlapping of the nylon-cement layers. Having finished the vertical shaft, I postponed digging the horizontal parts of the tunnel, giving priority to the construction of the above ground parts of the house.


* The House Foundation:


    The nylon-cement technique I was using for the main room included the use of a basket-like grid of iron construction rods about 10 inches apart, as in ferro-cement boat building. I was convinced that, because of the relatively thin walls, and the strength of the complex curvature, there would be little need for a massive foundation. The main purpose for the foundation would be to prevent undermining of the walls from erosion. I ended up doing a foundation only about a foot deep, and maybe eight inches wide.


     Suspended off the bottom of the foundation trench was an iron rod. Tie wired to that rod were pieces of rod shaped like staples, their legs aimed up. Those rod stubs were the base upon which further rods were tied to begin defining the walls-to-be. Although I didn't actually fill the foundation trench with concrete until most of the rod work was up, I now normally pour foundations, locking in the rod stubs, before defining the walls.

* Defining the Form of the House:

    Standard architecture, in most of the world, is composed of boxes, and I am more than a little tired of seeing so many boxes cluttering up the beauty of nature. To me, the most esthetically pleasing architecture is invisible architecture, or failing that, at least architecture that combines gracefully with nature.


     One sees very few straight lines in nature, and therefore all the straight lines in conventional architecture stand out like sore thumbs on the landscape. The flexibility of nylon-cement allowed me to compose using free-form curves, and irregular, sculptural forms, which combine much more gracefully into the environment.


     On the ground, nylon-cement is not poured into straight-edged wood molds, but is rather laminated over sculpted earth shapes. In the air, the easy shapes to make are domes, or tent shapes.


     Frames to define door openings were made out of welded pipe, and set in the foundation concrete. I experimented with a variety of heavy-duty hinge systems. Each of the doors is made in place out of cement, the same as the walls, and weighs on the average about 600 lbs.

For security, and other reasons, I decided not to have a lot of windows. There are some skylights (street light lenses) set into the walls with silicone rubber to avoid cracking from different thermal expansion rates. For the most part, the very large, gate-like doors take the place of windows.


     Surprisingly, there are not many truly bothersome insects out in my neck of the woods, if one is very careful not to breed mosquitoes in carelessly discarded trash. Living as far as I do from my nearest neighbors, I don't share the community mosquitoes that they breed. I have no need for screens on my windows, little to no need for a mosquito net at night, and I leave the doors open most of the time for ventilation. The line between indoors and outdoors is intentionally blurred in my house design.


     The design for my house evolved over time. Every morning, I would open the door to my original cabin, visualize the possibilities, and work spontaneously. There was no master plan, and directions were free to change as inspiration came. The construction process was a non-stop adventure.


     A normal house, given a construction crew, and a blueprint, goes up relatively quickly, and when things are up they tend to stay up. There is not much design flexibility once construction begins. Working alone with my new techniques, however, the form evolved fairly slowly in the first stage of making the iron rod support structure. Unlike a blueprint on paper, this 3-dimensional representation of what the house was going to be like could be walked through and experienced prior to finalizing the form with cement. If I rubbed my shoulder on the wall in passing, I could always untie the rods and change them.


     Just as boxes can be boring, perfectly symmetrical domes can get to be uninspiring also. Therefore, I distorted the basic dome concept in ways that helped better meet my needs and esthetics, and better conform the structure to the lay of the land.


     Storage of possessions is always a problem. In most houses, overhead space under the roof goes to waste. I solved a lot of my storage problem, and avoided the expense of cabinets throughout much of the house by setting iron rings in the walls and ceilings. The rings are firmly attached to the iron rods inside the walls, so they can support tremendous weight safely. Using iron "S" hooks, rope loops, and sometimes sacks, I can hang almost anything overhead (usually light-weight things) or on the walls. Also, to multiply the number of rings to hang things from overhead, I welded up big link chains out of more rod material, and attached the chain from ring to ring in the ceiling. Each link in the chain gave me a new point to hang things from.


     Another design element in the house is the sloping floor. The slope is not great enough to interfere with normal floor use, but it all slopes for drainage, so the house can be easily hosed out if desired. Also, the slope connects the patios on either side of the house in such a way that there are no steps to deal with in getting from one elevation to another.


     The traffic pattern in a boxy house tends to include a lot of right-angle turns. In my house, the traffic patterns tend to spiral around, with no need to slow down for corners. Also, there are changes in elevation that make for interesting variations in point of view. On the way up to the upper story bedroom, for example, after climbing the steps behind the vertical shaft, there is a stop at a loft area in the main room. The main room has a 15 ft. high ceiling. From the loft you can look down into the main room, and also about 40 ft. straight down to the bottom of the vertical shaft -- a breathtaking sight. A spiral stairway then leads up through a hole in the ceiling to the bedroom upstairs.


    The bedroom has a spectacular, treetop level view out over the valley, through big, cave-like window openings. The floor of the bedroom is domed, not flat, and the bed hangs off the floor by cables from the ceiling, and swings like a hammock. One has access to the rooftop by climbing out the windows and up a little stairway. Vines cover the exterior of the house, making it more invisible, shading it, and providing some fruit.


     I use both cement-base and elastomeric roof sealers on the exterior of the house. On the inside, I do not color surfaces with paint. Instead, I splatter on pigment-tinted cement. Interestingly, although I find that spiders build webs on painted surfaces, they don't seem to like raw cement. Without any maintenance, the walls and ceiling appear just as they did when new.


     My original plywood cabin served me well, and it was nice to have at least a little flat and level floor, and standard storage areas. Eventually, the plywood roof needed replacing, but by that time, it had been partially locked in by the cement part of the house, and could not be replaced without leak problems at the joint with the cement. I solved that problem by tearing off the rotten part of the roof, and building a whole new cement dome room which completely enclosed the old cabin and attached more easily to the newer, cement part of the house. The end result is a very interesting utilization of space, which combines boxy and rounded elements.

     To begin with, I removed some of the original plywood wall areas, to allow better ventilation in the room, and visual entertainment from see-through areas. Then, since the old plywood window closures were no longer needed, I removed them from their overhead, hinge-up positions, and moved them to the bottom of the window openings, suspended "outside" the openings for use as table surfaces. This gave me a lot of table area without sacrificing any floor space. Since the plywood room is up on stilts, one can easily walk underneath the tables on the other side of the wall.


* The Outdoor Bathroom:

     During my first years on the land, I had a very simple bathroom solution -- a shovel to dig and fill latrine holes in the woods. During that time, I came to prefer the spaciousness of my bathroom to the more cramped quarters you find at most homes. The sights and sounds of nature were more entertaining than wallpaper designs.


     When my mother decided to visit me, though, she informed me that a basic prerequisite for her visit would be a "civilized" flush toilet. Thus was born my compromise solution, which has become the most popular element of the house tour.


    First off, being the do-it-myself person that I am, I decided to make my own flush toilet. Secondly, since I would be the one using it most of the time, I decided to put it outdoors, where I liked being. Acknowledging that it is sometimes nice to have a roof over one's head when it rains, I also decided to put a sort of glass umbrella over it.


     The toilet bowl was formed with nylon-cement over a sand pile mold (kind of like a sand castle shape). The tank is a plastic drum with standard toilet valve hardware located at a sort of half way height between that of a modern toilet and the old chain-pull type. It has very good water pressure, and flushes nicely.

The septic tank next to the toilet is an eight-foot deep nylon-cement lined hole with a leach line, and is covered with a hollow fake rock with an access door. The bathroom area is quite large, and although open to sky, trees, and birds, is now completely surrounded by a privacy wall. The shower is in sort of a grotto area off to one side.

Bathroom maintenance is not very time consuming. There is no tile to clean. Basically, I just go in about once a month and rake the leaves out.

* Walkways, Stairs, and Retaining Walls:

Weeds grow fast where I live, and clay dirt trails can be slippery when it rains. To solve both problems, taking advantage of the economical nature of nylon-cement ( 1/4 inch of cement, and free, discarded fishnet ) I ended up plastering most of my trails and hillside stairways.

Usually, carving anything into a hillside results in a vertical cut face on the uphill side, and a need for a retaining wall to keep dirt from eroding down on the walkway below. With nylon-cement both horizontal and vertical surfaces can be plastered at the same time. Although retaining walls can be shaped in any form, I usually carve the dirt to look like rock boulders, to keep things looking natural.

To avoid erosion undercutting of the edges of patios, walkways, and retaining walls, I usually dig a shallow trench at the edge, and wrap the nylon-cement down into the trench. After back filling the trench, the edge is buried, and protected from undercutting.

Since I live in the mountains, a lot of my walkways include stairs. I have come up with an unusual stair design that is an improvement over normal stairs for steep slopes.

With normal parallel stairs, as the slope increases, the height of each step increases, and the available space for placing the foot decreases. My solution was to take the stairs and carve them in such a way that they intersect with each other at a 90-degree angle. That allows for more steps, so the height of each step is reduced. It also gives the diagonal distance on the step for placing the foot, so there is more room for the foot. Most visitors find the stair design to be more comfortable and safe than standard stairs would be on steep slopes.

* Trash Rocks:

Probably, one of my best ideas has been involved with trash disposal. Recycling, and the world's inundation by trash have been big concerns of mine over the years. On my personal level, I have solved that problem by making "trash rocks" out of the waste materials I cannot recycle otherwise.

To begin with, the nylon fishnet I use to make trash rocks is a discarded waste of the fishing industry. What I do is a constructive reuse of material that is otherwise not disposed of in ecologically sound ways. I cut out sections of net, and sew them into big sacks. I then fill the sacks with my un-recyclable trash, sew them closed, take them where I want them, and plaster them with cement.

The end results are cement "rocks" that can be used for benches, tables, statue bases, landscaping, or for building walls. They are strong, and have at least some thermal insulation.

* The Underground Tunnel:

Fortunately for me, the ground where I live is composed of clay soil and a relatively soft rock known as "tosca", which is kind of like hard clay. It is soft enough to dig through and, although there is always some risk of cave-ins, I felt secure enough tunneling through it as I aimed to connect with the bottom of the vertical shaft in the main room of the house.

After using some primitive surveying techniques to decide where to start the tunnel on the hillside, I dug a patio area where I could mix cement. Digging the patio also let me get to the tosca, below the soft topsoil layer, in order to safely begin tunneling.

The tunnel was designed with a slight slope toward the doorway, so that any water in the tunnel could always find its way out. Instead of making it a straight tunnel, I decided to make it snake around in an interesting way. I wanted walking through the tunnel to be an esthetic experience. Straight tunnels are not as interesting as curved ones.

The tunnel has, basically, an arched ceiling, which is a strong shape. It averages about 4 ft. wide, and about 7 ft. in height. The tunnel, from the hillside entrance to the vertical shaft, is about 100 ft. long. There is an oval room, about 8 ft. wide and 12 ft. long half way along the tunnel, and a branch tunnel that goes about 50 ft. off to one side. I suppose I have spent about 4 or 5 years working underground.

Due to entering soft material, and a cave-in problem at the end of that tunnel branch, I had to finish it by making another vertical shaft to the ground surface above, and covering the hole with a dome roof. It has a skylight, a ventilation opening, and an emergency escape hatch.

All branches of the tunnel have ventilation, which reduces humidity, but there is still too much humidity for leaving many things down there. Mildew does not attack cement, but it does attack most other materials. Even though I wouldn't live down there full time, it is a comfortable place to spend time and do things, especially during hot summer days.

* Technical Information:

I have left this technical information for last, since many people may not be interested in actually working with nylon-cement. For those who do love to roll up their sleeves and get on. I am, by no means, an engineering expert, but here are some of the game rules I have played by.

First, here is some basic information about cement. Sacks of cement, fresh from the production plant, are hot. Fresh cement is hot, dry, and powdery. From there on, a process of hydration and hardening up takes over. Whether or not it hardens up to the maximum depends on the conditions under which it absorbs water, and the time it has for crystals to form in the process.

In Puerto Rico, cement comes in paper sacks, with no plastic lining inside, so over time the cement can absorb water from the air and go bad. At first you find little rocks of hard cement mixed in with the powdered cement. Eventually, the whole sack hardens up. Obviously, you can't mix hard old cement like you can fresh cement, so you either want to use the cement as soon as possible, or you want to protect it from atmospheric humidity. This can be done by putting the sacks in plastic trash bags, or in my favorite containers, 5-gallon plastic buckets with lids.

When you mix cement with water, crystals begin to form within the cement, and eventually turn the cement into a rock-like substance. Cement begins to harden fairly quickly, and the hardening curve is pretty steep in the first few days, but then it levels off pretty much and only slowly reaches its maximum hardness, after about 28 days, I believe. Anyway, keeping the cement moist for the first day, or two is important. If it dries out, hardening stops, and getting it wet again doesn't continue the hardening process.

When cement dries out, it becomes a porous material. Between the latice-work of crystals, where the extra water was, air takes the water's place. The denser that latice of crystals is, the stronger the cement will be. For that reason it is good to not use more water than necessary when mixing cement. Runny cement has its uses at times, to penetrate where thicker cement won't go, but if thicker cement will do the job, use it.

When cement dries out, not only does it become porous, but it also shrinks. In order to avoid excessive shrinking, and cracking, a non-shrinking filler material has to be added to the cement. A good way to remember the correct ratios for mixing the components is to think "1-2-3". For mixing concrete (for foundations), it is 1 part cement, 2 parts sand, 3 parts gravel. For mixing cement for plastering (most nylon-cement uses), the ratio is 1 part cement (to) 3 parts sand.

Also, from what I have read, throwing in about a shovel full of construction lime to each sack of cement mixed for plastering will help the finished cement harden up more. The lime and cement react with carbon dioxide in the air to form the mineral aragonite. It is hard for me to tell the difference, but I always throw in a little lime when I mex cement for plastering jobs. Since this benefit of lime only works in the presence of atmospheric carbon dioxide, there is no reason to add lime to massive jobs of poured concrete in foundation ditches, etc.

I mixed all the cement for my house by hand. To do that, you need a good mixing surface (like my front patio area), a source of water, and a square-nose shovel. First, dump your sand on the mixing area and spread it out a little with the shovel. Then, dump your cement in the middle of that. Add a little lime, if you choose to. Walk around the pile, turning it over with the shovel to mix the dry materials. I usually make a little mound, tossing each shovel of sand and cement on the side of the pile, letting them mix as they slide down the side.

When you get the dry material roughly mixed and in a pile, take the shovel and open up a hole at the top of the pile. This is where you will add the water, filling it like a lake at the top of a volcano. Experience will tell you how much water to add, and usually the safest way to avoid adding too much water is to use less than necessary at first, adding more little by little until you get it right.

When the cement is mixed, shovel some into the buckets for carrying it to the work site (5 gallon plastic pails are what I use). Basic tools for plastering include a trowel (I make my own out of PVC plastic), and rubber gloves. Cement will eat holes in your skin, so be careful with it. Heavy-duty long-sleeve rubber gloves are best. Unfortunately, most stores only sell short-sleeve gloves. I sometimes cut the sleeves off of old gloves and use them as sleeve extensions, using heavy rubber bands I also cut from old rubber gloves to hold them in place.

To put a layer of nylon-cement on the ground, first you have to shape the ground. A pick, shovel, hoe and machete are useful shaping tools, and a broom tidies up the surface. Next, usually working in the late afternoon, so that the cement will harden in the cool humidity of the night without further attention from me, I splatter down a soupy "paint coat" of cement and water, flinging it down with a big cement worker's brush. If the color of the dirt shows through, the mixture is too watery. If it doesn't splatter easily, the mixture is too thick.

After letting the splash coat harden overnight, it can be walked on the next morning. Spread out the fishnet and trim the edges. If the fishnet has a very fine mesh, I sometimes do a first coat with soupy plastering mix, working it through the mesh with a gloved hand, and then a thicker, second coat immediately over that. To provide better traction, when the cement starts to harden up a little, I usually give it a little texture by brushing it with a broom.

When plastering fishnet in the air, it needs to have the weight supported until the cement hardens. If a grid-work of iron rod is used as the support material, I usually try to keep the tie wire snags on the inside of the structure, so that I can stretch the fishnet over the rods without dealing with snags all the time.

First, I stretch the fishnet and attach it to the rods with wire. The fishnet is still, basically, a loose skin over the rods. If one begins plastering the fishnet, from the bottom up, eventually the weight of the cement will stretch the fishnet, it will form ugly wrinkles, the cement will crack, fall off, and the air will be filled with foul language. To avoid that problem, one has to rub cement over the rods, through the fishnet, to adhere the netting to the rods. That way, after the cement hardens over the rods, whatever is done to any square in the grid will not affect neighboring squares.

Keeping in mind that one has to prepare the area that way in advance of plastering the walls, what I then do is plaster the outside as far up as I can reach the first day (using a gloved hand to apply the plaster and the trowel to smooth it some). On Day Two, I plaster the inside up to that height. On Day Three, I stand on a 55-gallon drum and plaster the outside as high as I can reach. On Day Four, I plaster the inside of that. On Day Five, I can lean a ladder against the wall and do the next stage. On Day Six, I plaster the inside of that. On Day Seven, I can start climbing onto the cement, and on alternating days do inside and outside until I reach the center. Toward the center of the roof, one needs bamboo poles, or other supports, to keep the weight of the cement from buckling the dome ceiling downward, until the cement hardens.

In plastering the underground tunnel, I had to use a modified technique, especially on the ceiling. Those who have ever plastered a ceiling know that some areas of wet plaster inevitably let go and plop to the ground. If they are connected to a big piece of fishnet, they can pull the whole thing down, which can be very, very frustrating. I solved that problem by using a two-stage plastering process, which also resulted in thicker and stronger walls. I also found that bigger mesh fishnet, about 1 1/2 or 2 inch mesh was best, because the cement has to penetrate the holes easily in order to stick to the ceiling and walls.

The two stages for tunnel plastering are as follows. First, the walls and ceiling are plastered without fishnet. Lots of staple-shaped pieces of wire are embedded in the cement, with their legs sticking out. When the cement hardens, these wires are used to hold the fishnet in place. If plaster on the ceiling lets go and starts to pull on the fishnet, the disaster will run only as far as the next holding wires. I have learned to use lots of these holding wire points in the ceiling.

The tent-like technique for above ground structures, which uses no iron rods, is actually pretty simple. One has to use a fine mesh netting. After locking the base of the netting into the foundation concrete, poles are used to stretch the netting out like a tent. Then, using a can on the end of a pole, runny plastering mix is dribbled over the tent. It can be applied by hand in areas where one doesn't have to lean against the structure. When the outside layer is hard, the inside can be plastered, leaving the removal of the poles, and touch-up in the cavities they make for last. In the garage I made with this technique, I used treated wood in the door frame, and stapled the fishnet to the wood.

* Some Final Thoughts:

To me, the extreme design flexibility of nylon-cement liberates fantasy. What I have done with it is only my fantasy. It would be fascinating to see a world that took nylon-cement potential to its limits.

One of my experiments was to put a dome on top of a dome; the bedroom on top of the main room. I can imagine cities built something like piles of soap suds, with dome rooms of different sizes, and ventilation and light access kept in mind with the over-all design. Such cities might grow over time, with people occupying the outer layers, and the more antique cores used for storage, or other purposes.

Given the usefulness of nylon-cement for lining tunnels, I can also imagine underground communities. There are already troglodyte communities in different parts of the world, mostly in drier climates than Puerto Rico, so maybe my underground humidity problem would not be a problem elsewhere.

Nylon-cement material, in thin layers on the ground, is also fairly easy to break up and remove, so that replacement as future needs evolve is not difficult. Old nylon-cement material makes pretty good fill material in roads, if nothing else.

Also, nylon-cement technology is not especially difficult, and the strength of the material can allow for practical success even in less than optimal designs. I think it would be a good self-sufficiency technique for all of society to know. It would perhaps reduce the need for contractors, for one thing, the cost of housing, and the cost of living. If children made their own schools with it, they would learn how to meet their own needs later in life.

Since cement doesn't have to be worked in large quantities at one time, it is potentially within the strength capabilities of women and children. Not only could it provide more independent self-sufficiency for people in general, but also for women in particular. Construction is, at the moment, a male-dominated industry. Nylon-cement techniques could change that.

My adventures with nylon-cement have provided me with some of the most interesting years of my life. Necessity being the mother of invention, I was always inventive, exploring for new and better ways of solving problems. The experiments were, for the most part, successful, and I hope my experience will inspire others to continue where I have left off. A free-form world of nylon-cement would certainly be an interesting world, and maybe a better one.