| WALLS & CEILINGS Magazine February 2000 |
"A Cure for the Common Wall"
by Sarah Mazure
Processes and techniques breathe new life into one of construction's oldest finishes.
An office building under construction in Southern California and a thousand-year-old church in Europe have something in common. Both are covered with the beauty of limestone.
But the newer structure, known by its address, 888 San Clemente, in Newport Beach, benefits from the use of a relatively new product that allows an installer to apply a limestone finish without pillaging or enslaving any hapless townspeople. It is covered with Le Décor, a product that offers the finish and durability of limestone sans the high costs and labor demands.
Le Décor, a recent import from France, has been used in Europe for approximately the last 15 years. One of the first contractors in the United States to use the product is The Raymond Group, of Orange, Calif. Raymond is applying the exterior on 888 San Clemente.
Applying the finish
Sean Tousseau, senior estimator for Raymond, says the application process on 888 San Clemente and the other limestone-finish buildings the contractor has completed or recently undertaken, began with a substrate system similar to standard commercial stucco systems.
Raymond's crew installed the metal-stud framing, the Dens-Glass sheathing board, and 3.4-pound galvanized metal lath with a cement scratch coat and fiber shorts. The only difference is that the metal stud framing system needs to be more rigid in Le Décor than a plaster system, Tousseau says. Le Décor requires L/480 studs, which provide lateral deflection, rather than the standard L/360 for plaster, to aid in minimizing cracking.
"Once we get past that point, we come in with the Le Décor limestone finish," he says. "The limestone mixture consists of one bag of hydraulic limestone binder to two bags of pure limestone aggregate. The portions are mixed together with water to a similar consistency of a plaster, and it is applied over the cement scratch coat with a nominal thickness of approximately a half-inch, either gun or hand applied.
"The material is applied to the wall, very similar to plaster, and after a two- to three-day initial curing we then use mechanical grinding wheels to remove the smooth surface. We sand off the smooth plaster skin to expose the limestone aggregate underneath."
The timing of the removal of the smooth surface is critical to the look and texture desired, Tousseau explains. "For example, for a medium-textured limestone finish, like we have on the office building, we would wait two to three days to start the sanding process. The longer you let it cure, the more of a honed finish you're going to get.
"After we've achieved the desired texture, we then lay out and utilize routers or saws to cut the desired grooves or joints," Tousseau continues. These grooves provide the look of limestone blocks, in either running-bond or stack-bond patterns, depending on the architect's specifications. 888 San Clemente called for a running-bond pattern. Raymond's crew uses a standard routed V joint, approximately 3/8-inch wide by 1/4 inch deep.
"It comes out of the bag an off-white color," says Tousseau. "We were the first to incorporate the use of a faux coloring technique and the use of mechanical tools for the cutting and grinding of the Le Décor system."
Once the desired textures, grooves and reveals are set, Raymond's team of artists moves in to complete the look. Using a Dunn Edwards custom acrylic sealer product tinted with standard paint pigments, they color the stone by hand, with rags, brushes and, in the case of 888 San Clemente, even sponges.
Making it
Raymond's color innovation is no surprise to Michel Couvreaux, president of TransMineral USA Inc., the Petaluma, Calif.-based supplier for Le Décor.
"Raymond spent a lot of time and money in development," Couvreaux says, referring to the 50 1-foot-by-1-foot samples of different colors and textures the contractor spent an entire year creating to win the bid on 888 San Clemente. "We have to teach that to the French people. In France, all the time it's the same. Here in the United States, we have a lot of different approaches."
Maybe that's because France and the rest of Europe are sticking to the plainer look that has served them well since the use of limestone in construction began 2,000 years ago.
"All of the old buildings in Europe are done with lime-based product," says Couvreaux. "The problem they have is that in the old times in order to have the binders, they had to cook the limestone. The cooking is a very important process."
But it was also a process that left a lot room for error, especially in controlling the slaking, which means re-adding the water after the limestone had been cooked in the oven and crushed. The result was buildings that still stand tall after 1,000 years, and some that crumbled right away. Today, Couvreaux explains, water is added by the drop and everything controlled by computer.
Once you mix this back together with water, the chemical composition turns back into limestone.
Today, Le Décor's creators understand that when they cook the material it loses its carbon dioxide content. Once they add water to the chemically hot material, the material cools. Carbon dioxide from the surrounding air returns to the mix naturally.
"It's an old technique that has been revived," Couvreaux says. "It has been perfected in the last 10 or 15 years. We know exactly what we're going to have, and that's the beauty of it."
Proven professionals
Le Décor doesn't trust this beauty to just any contractor.
"We must assure the quality of the people applying the product and the quality of the results," says Couvreaux. "We don't sell the product on the open market. The contractor has to be trained. Usually we choose one reputable contractor per state. It's a big incentive for them."
In addition to California, Le Décor's territory now covers Nevada, Oregon, Washington, Florida and Georgia. Operations are starting in Texas and Illinois. When Le Décor's careful growth is completed, it will have 50 major contractors installing its product, plus a number of smaller contractors for the residential market.
"We are very careful not to have conflict between the contractors," Couvreaux says. "We have all these contractors who are not in competition with one another. If one contractor finds a nice finish, he's going to share that with the other contractors."
Le Décor screens its contractors based on a number of factors.
"Mainly we look at companies where they have highly skilled plasterers to lead the teams," says Couvreaux. "They understand the tradition and they understand the time you need to work with the material. But it's not only a matter of skill level, it's finding someone who is very conscientious. The trick about the material is you cannot cut corners. They have to follow procedures, follow the rules."
They also have to follow their guts. They must be sensitive to the timing nuances of the textures and sanding, he explains. "A contractor who does not have that sensitivity is going to have a very hard time with the product."
As a contractor for a number of interior finishes and exterior finishes including stucco and EIFS, The Raymond Group considers Le Décor another option in its repertoire, as well as another option for owners who like the look of limestone, granite and precast but can't afford these high-ticket products.
Cost was the selling point for Le Décor on 888 San Clemente.
"Initially they wanted to use real limestone; it was over budget," says Tousseau. "Then they went to precast; that was over budget. When we went over the budget numbers on the limestone finish it was pretty close."
According to Jeff Larsen, senior associate partner at McLarand, Vasquez & Partners Inc., the Irvine, Calif., architect for 888 San Clemente, Le Décor proved to bring more to the building than the expected cost savings. It added a completely different look based on its ease of use.
"Returns and soffits are always really expensive to do on a limestone building," Larsen says. "If we were using a real limestone or cut stone material, the building would have to have been dimensionally flatter. It wouldn't have as many ins and outs."
These ins and outs include hundreds of returns around recessed windows, shaped sills and angular cornices, as well as terraces on each of the building's four floors, which offer a view of a golf course and the ocean.
"Le Décor added a lot of movement on the building," Larsen says of the classically inspired structure. "It allowed us to develop the kind of stone appearance we were after."
It also allowed building owners to command top prices for rent, based on all of the extras that became affordable, like the terraces.
"We wanted to take advantage of the climate and also the views," claims Larsen. "I would have had a building that wouldn't have been able to do that if we had stayed with the natural stone material."
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