Using greenboard as a tile substrate or a moisture barrier in showers has been a controversial topic in the construction industry. Greenboard is a type of drywall that is moisture-resistant, but it is not designed or intended for use in wet areas like showers. Instead, it is commonly used in areas with high humidity, such as bathrooms, to provide some resistance to moisture.
Here are some points to consider regarding the use of greenboard in showers:
1. Not Suitable for Wet Areas: While greenboard is more water-resistant than regular drywall, it is not completely waterproof. In a shower, where there's constant exposure to water, moisture can still penetrate through the greenboard, leading to potential water damage, mold growth, and structural issues over time.
2. Recommended Alternatives: The standard practice for shower walls is to use cement backer board (commonly known as cement board or tile backer board). Cement board is specifically designed for wet areas and provides an excellent substrate for tile installation. It does not deteriorate when exposed to moisture, making it a more suitable option for showers.
3. Waterproof Membrane: In addition to using an appropriate tile backer board, it's essential to use a waterproof membrane to protect the underlying structure from water infiltration. Common waterproofing materials include products like Schluter Kerdi, RedGard, or similar waterproofing membranes. Strato-mat, as you mentioned, might be one of those waterproofing membranes.
4. Follow Industry Standards: Building codes and industry best practices often dictate the appropriate materials and methods for constructing showers. It's crucial to adhere to these guidelines to ensure the long-term durability and safety of the shower.
5. Professional Installation: Regardless of the materials used, proper installation is critical. This includes ensuring the waterproofing is correctly applied, seams are sealed, and all components are integrated correctly to create a watertight enclosure.
In summary, while your builder may claim to use greenboard with a strato-mat membrane, it is not a recommended or standard practice for shower construction. To ensure a durable and watertight shower, it's best to use cement backer board as the substrate and apply a proper waterproofing membrane. If you have concerns about the materials used in your shower construction, it's essential to discuss them with a professional contractor or a certified tile installer to assess the situation and make any necessary improvements.