This is the third of a three-part series on Usonian concrete floors. Links to the other parts are at the bottom of this page.

Starting in the mid-1930s, concrete floors were an important component of a large majority of Wright’s subsequent buildings, both residential and non-residential. In the Usonian house, its concrete slab served as the the medium through which the house’s radiant heat flowed, it was the base for installation of the wood walls of the house and it was the finished surface of the floor. Wright’s practice of making construction elements serve multiple purposes is both a manifestation of his genius and a challenge to stewards as they maintain their buildings.

It cannot be overstated that each restoration project is different. There is no one solution that fits all projects. The information given here is to provide building stewards an understanding of the original, typical process of floor installation, show examples of restoration and an give an overview of common maintenance protocols. It is hoped this information will help inform building stewards as they plan their own restoration and maintenance strategies.

Feel free to share your comments and questions about this information through the link at the bottom of the this page.

Maintenance

Cleaning needs will vary from house to house. A public site will have much more traffic than single-family household. At two of the sites mentioned in the precious article the following products have been specified:

The Building Conservancy has conducted an informal survey of cleaning protocols used by building stewards. Comments included:

  • I vacuum and mop the floors using plain, warm water. We do not wear our outdoor shoes inside the home. I try to wax them every other year using a regular acrylic wax. I’ve found this is best done while the floor heat is off. Otherwise, the wax dries cloudy rather than clear.
  • Current maintenance protocol: cleaning, waxing, etc. We mop it with cold water biweekly; clean with vacuum and Swiffer as needed. We strip and renew the Johnson EZ-Care coating every five years.
  • When we completely re-poured the concrete floor of the living room wing, including the entranceway and hallway leading into it, back in the mid-eighties, a red powder called Corundum, a concrete hardener, an aggregate, that is available in various colors, was applied to the surface of the newly poured concrete [see the discussion of currently available products in parts 1 and 2 of this series]. And as we watched it instantly absorbed, we were confident that the surface would need no further treatment; and since then it has indeed remained unchanged, resistant to abrasion!! For the bedroom wing, Mr. Lindsay, a friend of Mr. Wright, and founder of Lindsay Paints, recommended a color to match that of the living room , an acrylic satin enamel called Krilguard! It has held up well and for both floors we continue to use nothing more than vinegar mixed in water for cleaning!! 1/4 of a cup of white vinegar to a quart of water.
  • I wax and polish the floors as needed by hand. I have run out of the original red wax used by the former owner. I mix a paste wax roughly 3:1 with a carefully chosen red shoe paste wav. This seems satisfactory. I have been unable to find a source for an appropriate red wax.
  • For interior floors, coat with paste wax, and follow by polishing. (We put on some old crew socks, and just dance around). Clean with wet swiffer, or mop with mild dish soap. Wax creates the right sheen and still allows the variation of color and texture to be revealed. Exterior floors exposed to the elements require a concrete sealer, which should be applied every year. I usually do this in the autumn. I use a semigloss to create a slight “wet look”.
  • We also tried waxing some of the floors with a colored wax but after a number of slips and one broken arm (not one of ours) we decided that wax was not a good solution with children, pets and nannies. Other than damp mopping the concrete every few weeks we plan to leave the floors as is. As mentioned earlier, we have come to like the lived in weathered look.

According to Jill Greenough at the Weltzheimer House in Oberlin, they use an Italian product called Livax Rossa from Nuncas. “This wax is the best we’ve found for color, no streaks, and no film build up.” Unfortunately, this product does not appear to be available in the US and may require a field trip.

Curator Nathaniel Allaire at Samara, the Christian House, provided a very complete synopsis of the protocol used there:

We have two regular maintenance measures on our interior concrete floors. Every two weeks between the months of April and November, we mop our floors with a soft nylon bristle broom and a water solution using lavender-scented Fabuloso (1/4 cup of Fabuloso with a gallon of water). Dr. Christian loved the lavender scent (along with fig, strawberry, and anything Hawaiian or Polynesian-like smells). We use the broom instead of a mop because it can clean the control joints well and doesn’t “wick” water onto the wood splashboard on the base cabinets. We do not wipe up the excess water and soap as the color tends to “lift” if wiped or scrubbed too vigorously. We allow the floor to air dry for 30 minutes, and we will open one window near the center of the house for 5 minutes.

About every eight months, we hand-apply a thick layer of S.C. Johnson paste wax with a rag using a circular motion. We let it dry for at least 5 minutes and work in 8’ sections. Then, we return with a lamb wool padded electric random orbital buffer at medium-high speed. (it is done by a handheld model, not a standing one). In corners where the buffer can’t reach, we use a horsehair brush using swift horizontal motions to buff those areas. A microfiber towel is used to blend the textures together. If space doesn’t allow for a swift motion, I have found using a felt dry eraser (used on whiteboards) will do the trick but will “clog” quickly with excess wax.
If we ever get “gunk” on the concrete (chewing gum, tree sap) or have wax that starts flaking and looks slightly brownish, we do a wax correction as needed. This involves boiling some hot water, dunking a terry rag into the water, and laying it down on the problem area. We will wet it, sit for 5 min, and then immediately use a plastic scraper (with an undamaged scrape edge) to scrape the old wax or gunk. Then, perform a rewaxing. We try to do this the least number of times we can, and we want the wax to build up and have that deep, slightly varied red color that Wright adored.

Regarding exterior concrete, it is a little tricky, and we are still figuring some things out. Generally, in the morning on days we have tours, we will use a low-powered leaf blower to clean any dirt, sand, or leaves from the concrete. On rainy days, we will keep a broom on hand to keep worms from the main walkway to the front door, so they don’t “crust” to the concrete. If there are bird droppings, we attend to those immediately by the end of the day using a non-scratch blue Scotch Brite sponge and a bucket of water. The yellow ones will leave micro scratches in the finish for some reason. Every spring (early April) we will spray the concrete down with some water and then mop with a short nylon bristle broom and a water solution using lavender-scented Fabuloso (1/4 cup of Fabuloso with a gallon of water). We clear leaves at least once a week from the lanai and terrace areas so leaves don’t adhere to the concrete and during the winter, we do not use sand or salt, ice chippers, or any snow blowers. If the snow is fluffy we will leaf blow the snow off from the main walkway. If the snow is wet we will use a plastic-blade (no metal) shovel and then a rubber squeegee to prevent ice formation. All floor mats outside (except at the front door) are brought inside during the winter or after a rainstorm; then, we will put them back down after the concrete has dried (usually a day).

When it came to wax, several respondents noted that care should be taken to avoid slippery floors. As one homeowner put it: “We also tried waxing some of the floors with a colored wax but after a number of slips and one broken arm (not one of ours) we decided that wax was not a good solution with children, pets and nannies.”

 

Exterior Maintenance

Maintaining exterior concrete is another challenge for building stewards. While continuity of floor finish from interior to exterior is an ideal, the obvious effects of the water, snow, salt and other elements will cause noticeable deterioration of exterior concrete.

At the Building Conservancy’s 2012 conference the late Dan Chrzanowski, Building Conservancy board member and owner of the Dobkins house, presented his experiences:

When we purchased the Dobkins house in 1997, it had all the usual problems associated with Wright houses of that vintage – poorly maintained flat roofs, deteriorating masonry and exterior wood in need of conservation. But while we were undertaking that restoration, I kept looking at the surfaces of the house’s three concrete terraces, which were covered with multiple coats of paint that had sadly deteriorated. A few cracks also existed, and the concrete’s module lines were filled with building sealants. In addition, the surfaces were covered with ground-in dirt, moss, mold and bacterial growth. Upon investigation, I discovered why the terraces looked as they did. The handyman charged with their maintenance simply swept the surface, popped a can of paint, and set to work, completing the job in less time than it took for another to cut the lawn – a clearly inadequate methodology. I set about remedying the situation, utilizing one approach among those available that proved to be satisfactory to myself and my wife. What follows is my suggested approach, should you choose the methods that I employed.
Although, in a climate such as we have in Ohio, actual work cannot start in the wintertime, that season offers a good opportunity to plan the task ahead, including the purchase of stain and sealer, which may be on sale at this time of year. Sherwin Williams carries the stain and sealer that I utilized, as well as most of the other necessary supplies.
Once you determine to commence the work, you will need patience, since the project requires low humidity and five to seven days of dry weather. First, the existing coatings will have to be stripped off. I used a strip-and-peel product called “Peel Away-1” that is manufactured by Dumond Chemicals and is available on Amazon, as well as other paint-stripping products, manufactured by Prosoco: Safety Peel-1 (which has a neutral pH), Saf Strip and Heavy Duty Paint Stripper. Some stripping products are highly alkaline, and will have to be neutralized so that the resulting surface has a neutral pH of 5.5 to 6.5. Otherwise, the coating will likely fail. PH papers and pens can be used to check the pH level. Neutralizing solutions can be made of one pound of baking soda and five gallons of water. All building sealants must also be removed. I found it useful to focus on completing one module at a time, so as not to become overwhelmed by the amount of work required.
Once the surface has been stripped, power wash two times at a low psi, using TSP, bleach (to remove any remaining mold and bacteria) and water. At this time, you may also wish to address cracks, opening them up, cleaning them, applying a bonding agent, letting the agent dry, and then filling the cracks with a Portland cement and sand mix. Alternatively, a silicone building sealant can be used. In my experience, small hairline cracks remain a perennial problem.
A minimum of two days with low humidity of 55% or less is then required for the concrete to dry, with temperatures of 55 to 90 degrees. Because of the climatic requirements, late spring or summer may provide the best time for the work, since falling flowers, leaves and pollen are a problem at other times.
Once the concrete is dry, stain can be applied. I used H&C solvent-based stain sealer. Spread the material on hands and knees with a brush and not with a roller or spray equipment, which requires too much masking. In areas where additional build-up was needed in fine recesses, I used a discarded plastic credit card. Be sure to have knee pads or some other cushion for your knees while applying the stain and sealer. A foam pad or cushion for the hand bearing your weight while you apply the materials is also helpful.
A minimum of two coats of stain sealer is necessary. Between coats, be sure to clean the surface. A leaf blower works well for that purpose. Module lines can be cleaned with a whisk broom. Once the work was completed, I have maintained it with a solution of four ounces of TSP, one quart of household bleach, and three quarts of water.
Postscript

  • I used “H&C (Low Organic Volatile) Stain and Sealer” purchased from Sherwin Williams. “Horney / Caruso” were the original producers of the product.
  • This is a single product…a stain and sealer all in one.
  • The Prosoco products are neutral ph.( a good thing) If an alkaline stripper is used , it is important to neutralize.
  • The H&C stain sealer is solvent-based. Xylene is the solvent.
  • After stripping and during the power washing stage I use TSP with household bleach.
  • I cannot stress enough the importance of proper preparation. The success or failure is not so much the product being used as it is on the prep work.

The late Dan Chrzanowski at work on the Dobkins House

At the Kraus House, stewards are in the process of discussing paths forward for the terrace concrete. It could be argued that the current condition of the concrete (as long as it is not a safety hazard or would promote additional deterioration to the house or terrace) is a natural function of the building’s age and should be left as is. The disparity between interior condition and exterior condition is highly noticeable. It can be argued that this is detracting from the mission of the site to interpret Wright’s design goals, which in this case would focus on continuity between interior and exterior.

Options for treatment include:

  • Complete removal and replacement of the concrete
  • Applying a tinted coating to the surface, such as was used at the the Christie House
  • Applying a clear coating to the surface to maintain the current condition and minimize future deterioration

As is usually the case with restoration options, each has its pros and cons. These will have be be weighed by the Kraus House stewards in the context of their overall conservation planning, as they decide how to move foreword.

Worn exterior concrete at the Kraus House

Interior concrete at the Kraus House

Please Note: Each restoration/maintenance/repair situation involving a Wright building requires analysis and research to identify the correct approach. The Conservancy is sharing the information so it may be of use to others as they evaluate their own specific situation and may consider these and other approaches. The Conservancy strongly recommends that owners consult with a design professional and an experienced contractor to determine which method is best for their specific projects.

Further, the provision of this information or mention of a specific product or products does not constitute endorsement, recommendation, preference or approval by the Conservancy.

Usonian Concrete Floors 101 - Part 1 Background and Original Installation

Usonian Concrete Floors 101 - Part 2 Repair and Restoration

Posted February 8, 2024