Manufactured stone is a very popular product for both the interior and exterior of homes and buildings. There are many manufacturers of this type of cladding system, Cultured Stone® and Coronado Stone® among the most recognized names. A man-made stone manufactured primarily for decorative purposes, these systems are typically comprised of cement, natural aggregates and iron pigments. In order to give manufactured stone a realistic appearance and shape it is often created by using molds of actual real natural stones. Like many building materials, the use of manufactured stone has both advantages and disadvantages, and installation is vital to its long term success.
The obvious benefit of using manufactured stone versus a natural stone is that manufactured stones are much less expensive and much lighter in weight than real stone. The lighter weight allows for an easier and quicker application as well as decreased load on the foundation of the building. When using manufactured stone, there is typically no ledge required on the foundation as would typically be needed for a brick or natural stone installation. The back of the manufactured stone product is flat allowing for surface contact with base coat and installation similar to that of stucco.
A manufactured stone cladding on the exterior of a home or building is aesthetically pleasing and many developers have recently preferred to use manufactured stone over stucco or an EIFS system due to the perception of potential buyers regarding the past problems that have been related to stucco or EIFS applications. The problems with these systems are well documented and include improper and/or inadequate drainage, expansion joints, caulking around windows and doors and/or no flashings at all in critical areas. This has resulted in water infiltration, structural damage and/or mold conditions.
Unfortunately, manufactured stone is installed in a manner similar as stucco and improper installation can result in similar deficient conditions. It is essentially a porous system that can absorb moisture rather than repel it. Therefore manufactured stone should be installed with a suitable drainage plane and detailing that will help drain water that does get behind the stone to escape through weep holes above windows and doors and through a weep screed set above grade at the bottom of the facade.
Manufactured stone may also experience problems related to cracking. The cracks are typically in the mortar joints between the stones or at the interfaces of dissimilar materials. The cracks will also allow water into the system and may cause significant damage if the underlying drainage system is deficient. Cracks occur when the masonry expands and contracts in response to temperature and moisture changes.
Since water expands when it freezes it will expand the crack up to nine times its original size. Proper mortar mixes and sealants should be used.
Properly installed water resistive barriers and flashings are required to protect the underlying wall from any potential water infiltration. One layer of water resistive barrier is not adequate, two layers are required.
Ideally, manufactured stone should have even more stringent installation detailing compared to that of a stucco or EIFS system because it has some characteristics that help create a more stressful moisture load for walls during wet weather. Manufactured stone is a cement based product that absorbs and holds water.
The thickness of the manufactured stone wall also makes installing the recommended flashings more problematic. If the recommended flashings are not installed as specified, it can be as large of a problem (and maybe worse) than not installing any flashings, as incorrect flashing details may actually trap water.
All flashing areas are critical for manufactured stone installation. The water resistive barrier particularly at window or door sills should extend to the window's edge in such a way that the window flange directs water on top of the water resistive barrier instead of behind the water resistive barrier. Manufactured stone veneer should also have weeps installed at any termination such as windows, doors and a weep screed at the bottom of any system installed above grade. Proper flashing around building penetrations is important as well. Weather and temperature at the time of installation should be closely monitored.
Intersecting dissimilar materials such as manufactured stone and vinyl siding have characteristics that react differently to changes in weather, especially temperature. There are often problems that arise if the joints where these veneers meet are not properly detailed, which can result in a strong possibility of water infiltration at that area.
Manufactured stone can result in a very appealing building appearance and can even be installed to give an older building a new look. There are many styles and textures to choose from allowing for a wide array of appearances. If installed properly, the system has an extended useful life and requires little maintenance; however, if the detailing of the installation of manufactured stone is not proper, trapped water can occur which can lead to damage, water infiltration into the building envelope or even mold growth. Often times, as is the case with stucco or EIFS systems, the problems may not actually surface for years. It is critical that a proper design and specification are followed by experienced installers. It is equally important that the specifics of the building architecture are taken into account to ensure any special detailing is also provided.
Some typical signs of improper installation are:
- Manufactured stone installed directly on top of the roof system.
- Manufactured stone below grade.
- No signs of weep holes along the tops of windows and doors.
- No joints between windows, doors, dissimilar materials and the stone.
- No/improper flashing between the roof/wall flashing and the gutter that abuts the wall.
Damage can be repaired if the problems are caught early on, but this is a far more expensive way to correct the problem then would be the case if the products are properly installed originally.
Several building codes have requirements which relate to manufactured stone veneer, but they are often not enforced. The codes help protect the consumer and assist in understanding the quality of the product they are receiving. The codes prescribe physical and performance characteristics, installation requirements and even raw materials and quality control processes. As stated earlier, when it comes to manufactured stone veneer, most inspectors do not understand the requirements and, as a result, do not focus on enforcement. This potentially creates a credibility/confidence gap for the industry.
Use of non-compliant products can lead to headaches for everyone, including (but not limited to) material failures, warranty claims, expensive tear off and replacement, job stop and liability.