The Ennis House Slabs

Making Faux Concrete in Memory of

Frank Lloyd Wright...

 

In 1924, Frank Lloyd Wright, the scion of American architecture, built a house for Charles Ennis in Los Angeles. The architect and his client were of one mind that the house should reflect a pre-Columbian style. Wright used a unique cast concrete "textile block" technique to create a structure evocative of a sacred Mayan temple. His result seems uncanny and fascinating even today. It has no match in the 80 years since its construction. Look at some images of this remarkable dwelling:

You may not realize it, but you likely have seen this house before. The interior has served as the backdrop for many movies, commercials and music videos. You can see it in Blade Runner, Twin Peaks, House 2, and more than 3 dozen other Hollywood productions. Do you recall now the subliminal memory of those repetitive, Mayanlike blocks that comprise the walls and columns of the entire house? Imagine how cool it would be to spend a quiet evening alone in this dwelling!

I wanted to recreate this particular cast "textile block" motif inside my own home, in vertical fashion on one particular high, narrow wall section in our living area. The original Ennis slabs were about 16" square, probably not more than an inch or two thick, and mine would be roughly the same dimension. I needed to somehow stack them on top of each other and attach them to sheetrock, so they had to be really light. But I wanted to copy the same rough concrete/stone look, texture, "apparent" mass and ancient-seeming age of the originals. I needed to achieve the same depth of relief on my slabs. So I studied photos of the original Ennis block details carefully. I was able to glean enough information from photographic images to let me figure the proportions of the details and the likely "elevation" of each layer of the relief.

I created a crude plan for making a positive model for the mold for my slabs. Looking at it again 10 years later, I am guessing the numbers represented the measurements I took off the photo I was using, to be scaled up to whatever size the final block would be. And I reckon the colors must have been a code for the relief height. I fabricated a full-scale positive model using thin, flat lath molding nailed to a square wood panel. I added a gracious draft angle to the sides of all the pieces using wood filler, and used filler in any gaps and cracks in the pieces to allow easy parting of the eventual casting. I slapped about 3 separate coats of varnish on it to make it really smooth and slick. Then I clamped sides around the model, greased it up real good with petroleum jelly, and poured regular artist's plaster of paris onto it. I think I recall putting some thin metal tubes in there to act as reinforcing "rebar". Once dry, I managed to carefully pry the hardened plaster away from the model without breaking it. It was pretty heavy; I hadn't scrimped on the paster.

Up to this point, I didn't have a concrete notion (pun intended) as to what the actual molding material would be. Pure plaster would be much too heavy, and the pure white finish would not look much like old concrete, much less ancient Mayan stone. But I knew a plaster base would probably be best, possibly mixed with a matrix of something else, with a lot of air inside. So I bought a huge bag of cellulose-based insulating material - you can't buy a small bag, but it was dirt-cheap nonetheless. This stuff is made from finely shredded newsprint. You can still see printed letters on some of the wee pieces of paper. There are also tiny bits of more colorful materials, possibly rags or other type of colored paper stock. The shreds are really mixed together thoroughly and are fluffy as all getout -- it's insulation, after all. A huge bag of it is light as a feather!

I did a lot of experiments to try to determine the proportions of cellulose and plaster to use, to get something that would have enough strength to stay together and not be too brittle once it dried. This mix was basically just papier maché that you knew and loved as a kid. But papier maché, while light in weight, is very crumbly and doesn't have very good strength. I wasn't hitting on any successful combination of these two ingredients, so I started adding other things to the mix. When I tried some liquid latex floor leverer additive that I had leftover from a previous fixup job, that seemed to do the trick. Here is the final formula for my casting media:

    3 parts (by volume) of cellulose (newsprint) insulation
    1 part (by volume) of Plaster of Paris
    15-20% latex leveler solution (diluted with water)

I made removable side boards to go around the plaster mold. I then smeared a liberal application of petroleum jelly over the surfaces of the mold as a parting compound, topped with a good stiff shot of canned spray silicone -- just to make sure. I put a batch of the dry cellulose insulation, measured out by volume (in an uncompressed "fluffed" state), into a pail, added the plaster of paris, then mixed thoroughly so that the cellulose was well-coated with the white plaster particles. I "laid up" the dry material a small handful at a time into the mold, starting in a corner, and used a garden sprayer to soak each handful down with the latex solution. I tamped it down with my fingers good and hard when it was soaked. I continued to add the material and spray it, handful at a time, until I reached a marked line on the sides of the mold, making the slab about an inch thick. According to my notes, it took a total of about 30 ea. 16-oz. containers of cellulose for each slab. (But there were about a million ounces in the bag I bought!) The smell of the latex was pretty overpowering until it dried completely -- that took several days.

I found I could remove the mold sides immediately to help the material dry -- I can be a very impatient person. It took at least 30 minutes before the slab had hardened enough to remove it safely from the mold. I did this very carefully, using a flat paint scraper around the edges to aid its release. I trimmed the ragged edges around the back side a bit to make the edge thickness a little more consistent all around. The front side was a joy to behold: You would swear this was old concrete! The grey tones and tiny speckles of different colors were great.

So I was well-pleased with the "concrete" appearance of this medium. And best of all, it was light, light, light -- and pretty darned sturdy. The latex addition did a good job in giving the slab some tensile strength; the end result was not brittle at all.

To attach the slabs to the wall, I drilled two small holes in the top and bottom edges of each slab at a certain distance from each side, to accept a short stud. I sawed off the heads of of some long, skinny threaded toggle bolt screws, and installed them in small metal L-brackets using little lock nuts. The attachment of the slabs was sequential, from the bottom to the top of the column. The nice thing about this hardware arrangement was that I could butt the slabs up almost right next to each other, going up the wall. The hardware is virtually invisible:

I was pretty proud of the results. Here are a couple of photos I took of the final "Mayan column":

 

Postscript: The Ennis house suffered some significant damage in a 1994 earthquake, and is being restored through contributions from private citizens and some grants from philanthropic organizations. You can "adopt a block" to help this important preservation project along. See the links page.

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Interior Ennis House photograph from Frank Lloyd Wright Design, Maria Costantino (Barnes & Noble Bookds, 1993)