Something different in these four walls

July 20, 2005

By DANE GOLDEN
ARGUS-COURIER STAFF

What do the Arc de Triomphe, the Mission San Juan Capistrano, the Petaluma Library and a King Street home built from bales of straw have in common?

They all use St. Astier lime plaster, extracted from the same mine in the Bordeaux region of France.

Lime plaster is an age-old type of wall exterior, which is gaining a renewed foothold in the U.S. as it is becoming used in place of concrete stucco. And it's an example of how we can look to history to help us in the future.

In the United States, the St. Astier lime plaster is distributed by one company, TransMineral USA of Petaluma, owned by Michel Couvreux.

Couvreux, a resident of Petaluma and a native of Bordeaux, said the natural hydraulic lime (also known as NHL), has been extracted from the same mine since 1851, and has been used to restore all the great monuments of France. Since he began offering it in the U.S. in 1997, American contractors have begun using it to restore treasured older American structures and to build new, environmentally sound homes and commercial buildings.

NHL is becoming a favored product of the Green movement, in part because its production process creates 80 percent less carbon dioxide than cement. It has been used with success in the construction of homes made from straw bale construction, a growing trend in environmentally conscious building. The overall cost of NHL is 15 percent higher than concrete.

"Any common contractor can use it," said Couvreux.

As long as they follow the guidelines, that is. Since most U.S. contractors haven't worked with the older process, they need to follow the simple, but specific process of the all-natural product.

"We don't have any additives to compensate for people who want to cut corners," he said. But he makes it clear that the results are well worth the small effort it takes to learn the process.

As Couvreux explains it, lime plaster was commonly used in the United States until the late 1900s, when stronger concrete use developed as a method for building our early skyscrapers. The use of lime plaster gradually fell away, essentially becoming extinct in America. But its use is making resurgence for several reasons; it pollutes less in production, it's more malleable, and it breathes. And when used as a plaster in place of stucco, it's longer lasting,

Lime is also very helpful when it comes to using mortar between bricks on masonry buildings, or plaster in place of stucco, because as a structure settles, lime moves with it, instead of cracking, which causes weakness. Additionally, lime is a more breathable product, so it is a preventative measure against dry rot and mold.

"It is a catastrophe," said Couvreux, when concrete is used to repair these older masonry structures.

NHL is not without its challenges, though. One problem is that while lime becomes somewhat hard initially, it gains its greatest strength over time, not reaching full strength for up to two years. This has created more than one misunderstanding with building inspectors, who are often unknowledgeable about the product. But after Couvreux describes the process to them, they always approve the structures.

Since there are no additives used in St. Astier natural hydraulic lime, and it breathes so well, Couvreux is also promoting its use in wine cellars as a preventative measure against TCA, a problem of cork contamination. Lime floors are more frequently seen in European wine cellars.

(Contact Dane Golden at dgolden@arguscourier.com)

TRANSMINERAL USA

President: Michel Couvreux

Founded: 1997

Location: 201 Purrington Road

Employees: 2

Phone: 769-0661

Web: www.limes.us

PETALUMA BUSINESSPERSON PROFILE:

MICHEL COUVREUX

A resident of Petaluma but raised in France's Bordeaux region, Couvreux received his masters in architecture at L'école des Beaux-Arts de Bordeaux. He sailed around the world for eight years with his wife Janis and their two sons. In 1990, they moved to Sonoma County and Michel restarted his architecture practice. In 1997 he became a distributor of St. Astier natural hydraulic lime. He enjoys the small town feel of Petaluma and that it has a lot of very nice, open-minded people. He also enjoys the climate. One of his sons is a sailor on the America's cup K-Challenge team, and the other is studying kinesiology at UCSF.