Stucco is a very fashionable building material. In my opinion, it is the chameleon of building materials. In other words, stucco looks just as good on a southwestern style house as it does on a stately English Tudor home. Textures and patterns are infinite in most cases. The talents of the applicator are your only restraint. The durability and beauty of the product was discovered thousands of years ago. Time has simply allowed us to improve the materials and methods of installation.
The Two Types
Stucco is available in two basic forms: cement and synthetic. Cement stucco has been available for thousands of years. It is simply a mixture of Portland cement, sand and lime. Basically it is just fine grained concrete. When it dries it is very hard and durable.
In the early 1970's, synthetic stucco, or EIFS, made its debut.This product is a stucco material used in conjunction with an insulation system. A building is first covered with foam insulation sheets and then with a thin one or two coat layer of synthetic stucco. The use of foam allows a building to be super insulated. In addition, the foam can be layered and sculpted to produce interesting designs and shapes.
Synthetic stucco was a branch of the plastics industry explosion of the 1960's and 70's. The plastics industry was churning out a multitude of products and they took a stab at the stucco market. The synthetic stuccos are primarily acrylic co-polymers which are durable plastics. It worked. The synthetic stucco compounds proved to be super durable and waterproof. In fact, they were too waterproof!
Old Lessons Forgotten
As synthetic stucco usage expanded, the manufacturers seemed to forget lessons learned by the cement stucco installers. The cement stucco industry had long ago learned how to control water infiltration into their systems. They knew that if you didn't control and rechannel the water back to the surface, there could be catastrophic damage to the wood framing systems behind the stucco. The old cement stucco masons used tar paper and metal flashings. In addition, the cement stucco was a breathable material. If it got wet or saturated, it would allow the trapped water vapor to escape to the exterior, even if painted. The synthetic stucco people didn't seem to pay attention to these details.
What's Rotten in NC?
There has been much publicity lately about discoveries with rot problems in conjunction with EIFS houses in North Carolina. A random check of other houses across the USA that are covered with EIFS found similar problems. The EIFS material, the acrylic polymers, seem to work too well. They will not allow water to easily escape. In fact, some allow virtually no water vapor transmission whatsoever. Furthermore, several major manufacturers abandoned the use of any waterproof membrane or paper between the wood framing and the insulation board. Thus, if water enters the system around a window, door, flashing, etc. It can begin to damage the structure from the inside out!
Water Management Systems
The USG Corporation conducted a study not too long ago. The results of their study prompted them to be the first company to react to the deficiencies of the first EIFS products. They currently are the only EIFS manufacturer that is producing a total system which utilizes the lessons learned over time by the cement stucco masons. Their EIFS system promotes the use of a breathable acrylic compound, the use of cement board and insulation board as a substrate, a water barrier paper and metal flashings. It is my understanding, that the other major manufacturers are rapidly modifying their product line in response to the rot problems.
The Bottom Line
Stucco is a great material. If you have it installed correctly, it will very likely outlast you. The key is to choose which material suits your tastes. Then make sure you install it so that water which will invariably get behind the stucco can get out before it damages the wood framing of your home.